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Is CO2 a good proxy for indoor air quality in classrooms? Part 1: The interrelationships between thermal conditions, CO2 levels, ventilation rates and selected indoor pollutants
Abstract
Current indoor air quality (IAQ) guidelines in school buildings are framed around thermal conditions, carbon dioxide (CO2) levels and corresponding ventilation rates without considering specific indoor pollution levels. Drawing on detailed monitoring data from a sample of 18 classrooms from six London schools, the aim of this paper is to highlight behavioural and environmental factors that affect pollution levels in classrooms, and evaluate the adequacy of CO2 as an overall predictor for IAQ using multilevel modelling. Together with elimination of indoor emission sources, keeping the temperatures below 26℃, and preferably below 22℃ depending on season, may limit total volatile organic compounds below thresholds associated with sensory irritations. The models suggested that after removing dust reservoirs from the classrooms, lowering average indoor CO2 levels below 1000 ppm by increasing ventilation rates can limit indoor airborne particulate matter concentrations below recommended annual WHO 2010 guidelines. Uncontrolled infiltration rates may increase indoor NO2 levels and microbial counts of fungal and bacterial groups, whose presence is associated with wet and moist materials. Overall, indoor CO2 levels were a useful proxy for indoor investigations as they can prevent overheating, dilute pollutants with indoor sources and purge concentrations of airborne particles; however, they were a poor predictor of traffic related pollutants. Practical implications of the findings on the UK policy and building design industry are discussed.
... Previous research conducted by Chatzidiakou et al. [17,18] found that CO 2 can be used as a proxy for indoor air quality in classrooms, considering that low CO 2 concentration is correlated with the dilution of indoor pollutants and the purge of airborne particles. It is relevant to note that, although a correlation between CO 2 concentration and cognitive performance has been found [19], it is not clear that CO 2 concentration is the cause of the decline in performance [20]; therefore, CO 2 is considered a proxy for indoor air quality [17,18,[21][22][23][24], not as a contaminant. ...
... Previous research conducted by Chatzidiakou et al. [17,18] found that CO 2 can be used as a proxy for indoor air quality in classrooms, considering that low CO 2 concentration is correlated with the dilution of indoor pollutants and the purge of airborne particles. It is relevant to note that, although a correlation between CO 2 concentration and cognitive performance has been found [19], it is not clear that CO 2 concentration is the cause of the decline in performance [20]; therefore, CO 2 is considered a proxy for indoor air quality [17,18,[21][22][23][24], not as a contaminant. ...
... Measurements were obtained using a Delta Ohm HD32.3 instrument that registered dry bulb temperature (Ta), globe temperature (Tg), relative humidity (RH), and air velocity (Va) at 5 min intervals during the occupied period (0900 to 1500) in all classrooms. CO 2 concentration was measured with Hobo Carbon Dioxide Logger at the same interval, considering it as a proxy for indoor air quality [17,18,[21][22][23][24], not as a contaminant. Table 3 summarizes the characteristics of the equipment. ...
Between the ages of 6 and 18, children spend between 30 and 42 h a week at school, mostly indoors, where indoor environmental quality is usually deficient and does not favor learning. The difficulty of delivering indoor air quality (IAQ) in learning facilities is related to high occupancy rates and low interaction levels with windows. In non-industrialized countries, as in the cases presented, most classrooms have no mechanical ventilation, due to energy poverty and lack of normative requirements. This fact heavily impacts the indoor air quality and students' learning outcomes. The aim of the paper is to identify the factors that determine acceptable CO 2 concentrations. Therefore, it studies air quality in free-running and naturally ventilated primary schools in Chile, aiming to identify the impact of contextual, occupant, and building design factors, using CO2 concentration as a proxy for IAQ. The monitoring of CO2 , temperature, and humidity revealed that indoor air CO 2 concentration is above 1400 ppm most of the time, with peaks of 5000 ppm during the day, especially in winter. The statistical analysis indicates that CO2 is dependent on climate, seasonality, and indoor temperature, while it is independent of outside temperature in heated classrooms. The odds of having acceptable concentrations of CO2 are bigger when indoor temperatures are high, and there is a need to ventilate for cooling.
... 1) Selected schools in this study are naturally ventilated as the main source of ventilation in most UK schools is windows. Variations in temperature, relative humidity and indoor pollutants from mechanical ventilation and air-conditioning (MVAC) [55][56][57] can limit the understanding of buildingrelated factors on VRs, therefore naturally ventilated buildings are selected for the aim of this study. ...
... Selected schools are within a considerable distance to the main road to have the regional Road Noise, LAeq 16h, less than 55dB according to England Noise Map Viewer [64]. 3) Schools were selected in areas with low Daily Air Quality Index (DAQI) according to Air pollution Forecast by the Met Office [65], because window operation can be limited due to pollution or odour [21,51,55,60,61,66]. 4) Buildings were selected with different architectural features so that different potentials for ABs and natural ventilation are provided. ...
... Concerns about global warming, energy consumption and maintaining a healthy indoor environment have resulted in a growing interest in NV buildings [50,51,111]. However, natural ventilation is affected by contextual factors [52]; it can only be applied to certain climates [50][51][52] and it might be limited due to high background noise level [21,49,51,[58][59][60][61][62] or pollution [21,51,55,60,61] because 'outdoor air' into the building may not be 'fresh air' [26,27]. Therefore, this study, as explained in methodology, has selected schools in low-polluted and quiet areas. ...
Indoor Air Quality (IAQ) in classrooms is assessed by CO2 levels and Ventilation Rates (VRs). Factors affecting VRs fall into Contextual, Occupant and Building (COB) related factors. This study investigates how VRs are affected by COB factors in 29 naturally-ventilated classrooms in the UK during Non-Heating and Heating seasons. Building-related factors classify classrooms with high or low potentials for natural ventilation, with 45% of classrooms having high potentials. Contextual factors including season, operative temperature (Top), outdoor temperature (Tout), ‘Top-Tout’ and air density can limit or increase VRs. Occupant-related factors classify occupant's good or poor practice of environmental adaptive behaviours. ‘Open area’ as a reflection of all COB factors is strongly correlated with ventilation rates. Results show that 12% and 19% of variations in ventilation rates are explained by open areas during non-heating and heating seasons, respectively. Findings highlight that to have VR of 8 ± 1.28 l/s.p during non-heating seasons and VR of 8 ± 1.07 l/s.p during heating seasons, average open areas of 3.8 m2 and 2 m2 are required, respectively. This difference can mostly be explained by temperature difference between inside and outside. Results show COB factors need to be considered holistically to maintain adequate VRs. Classrooms in which all COB factors are met provide average VR of 11 l/s.p and classrooms in which none of COB factors are met provide average VR is 3.1 l/s.p. This study highlights that 40% of classrooms according to EN 13779 and 80% of classrooms according to ASHRAE Standard fail to provide adequate VRs.
... Adequate ventilation must be ensured for providing safer and healthier classroom environment for students, because during classroom hours, the occupation density is high (close to 1.8 m 2 /pupil) and students inhale more indoor air (Theodosiou and Ordoumpozanis, 2008). Although CO 2 is not an air pollutant, but still can be considered as a proxy for classroom air quality (Chatzidiakou et al., 2015), maintaining proper ventilation to maintain better air quality in classroom. Majd et al. (2019) found that physical defects in the school building, such as cracks and holes in the walls, broken windows and peeling wallpaper or paint, were associated with higher indoor NO 2 concentrations. ...
... School playgrounds expose children to particulate matter and other vehicular emissions due to their closer proximity to roads or their location along a major road (Famuyiwa et al., 2018).. Some other structural measures include relocating the playgrounds and free flow spaces to the less polluted areas of the school premises, relocating pedestrian entrance, co-ordinating start and finish time with nearby schools, and providing additional space for scooter or cycle parking (Toolkit, 2018). Chatzidiakou et al. (2015) found in their study that providing hard-tiles flooring may lead to an average of 38 μg/m 3 and 29 μg/m 3 lower indoor PM 10 and PM 1 respectively, as compared to the carpeted floor. They suggested that replacing the carpeted floor with hard-tiles, proper selection of cleaning products and fleecy cleaning cloth introduced in the classroom can limit the exposure to TVOCs.. School buildings play an important role in maintaining better IAQ and to prevent health problems in students, therefore, school infrastructure upgradation should be carried out by schools at regular interval. ...
Students spend nearly one third of their typical day in the school environment, where they may be exposed to harmful air pollutants. A consolidated knowledge base of interventions to reduce this exposure is required for making informed decisions on their implementation and wider uptake. We attempt to fill this knowledge gap by synthesising the existing scientific literature on different school-based air pollution exposure interventions, their efficiency, suitability, and limitations. We assessed technological (air purifiers, HVAC - Heating Ventilation and Air Conditioning etc.), behavioural, green infrastructure, structural, school-commute and policy and regulatory interventions. Studies suggest that the removal efficiency of air purifiers for PM2.5, PM10, PM1 and BC can be up to 57 %, 34 %, 70 % and 58 %, respectively, depending on the air purification technology compared with control levels in classroom. The HVAC system combined with high efficiency filters has BC, PM10 and PM2.5 removal efficiency up to 97 %, 34 % and 30 %, respectively. Citizen science campaigns are effective in reducing the indoor air pollutants' exposure up to 94 %. The concentration of PM10, NO2, O3, BC and PNC can be reduced by up to 60 %, 59 %, 16 %, 63 % and 77 %, respectively as compared to control conditions, by installing green infrastructure (GI) as a physical barrier. School commute interventions can reduce NO2 concentration by up to 23 %. The in-cabin concentration reduction of up to 77 % for PM2.5, 43 % for PNC, 89 % for BC, 74 % for PM10 and 75 % for NO2, along with 94 % reduction in tailpipe emission of total particles, can be achieved using clean fuels and retrofits. No stand-alone method is found as the absolute solution for controlling pollutants exposure, their combined application can be effective in most of the scenarios. More research is needed on assessing combined interventions, and their operational synchronisation for getting the optimum results.
... The CO 2 concentration is an indicator of the retention of harmful substances, as its concentration increases with inadequate ventilation in buildings [18][19][20][21][22]. Many countries have regulatory standards and guidelines to maintain CO 2 concentrations below a fixed level (around 1000 to 1500 ppm) within buildings such as offices, schools, and houses [18,22,23]. ...
... 2.1. CO 2 Concentration as an Indicator of IAQ CO 2 concentration is widely utilized as a comprehensive indicator of air pollution in IAQ [18][19][20][21][22]. Table 1 summarizes the CO 2 concentration standards and guidelines for various countries [18,22,23]. ...
Indoor air quality (IAQ) in houses is often deteriorated by chemical substances emitted from heating, building materials, or other household goods. Since it is difficult for occupants to recognize air pollution, they rarely understand the actual conditions of the IAQ. An investigation into the actual condition of IAQ in houses was therefore conducted in this study. Carbon dioxide (CO2) concentrations in 24 occupied houses was measured, and the results from our analysis showed that the use of combustion heaters increased the concentration of CO2 and led to indoor air pollution. Results indicate that as outdoor temperature decreased, the frequency of ventilation decreased simultaneously, and CO2 concentration increased. Results of the questionnaire survey revealed that the actual IAQ in each house did not match the level of awareness its occupants had regarding ventilation. Along with this difficulty in perceiving air pollution, the lack of knowledge about ventilation systems and the effects of combustion heating may be additional barriers to IAQ awareness.
... Seppänen, Fisk, and Lei [23] conducted 24 case studies and concluded that a 2% decrease in productivity is observed for a 1 °C increase in air temperature above 25 °C. Charzidiakou et al. [24] suggest that IEQ assessments be mandatory as part of building regulations due to the interrelationship between thermal condition, indoor pollutant levels, ventilation rates, and CO2 concentration. In their studies focusing on educational buildings, it is observed that keeping temperatures below 26 °C in summer and 22 °C in winter by outdoor air ventilation can limit the amount of Volatile Organic Compounds (VOC) below the threshold, above which sensory irritation is likely to occur. ...
... There is a correlation between high indoor air temperature and occupants' productivity as noted by Singh, Ooka, and Rijal [18]. Indoor air temperature and CO2 concentration may be related because there is a higher likelihood of a space overheating above 25 °C when CO2 concentration are above 1500 ppm [24]. Persily and de Jonge [5] identify that CO2 accumulation in the space from occupants can cause indoor air quality concerns. ...
Indoor air quality and thermal conditions are important considerations when designing indoor spaces to ensure occupant health, satisfaction, and productivity. Carbon dioxide (CO2) concentration and indoor air temperature are two measurable parameters to assess air quality and thermal conditions within a space. Occupants are progressively affected by the indoor environment as the time spent indoors prolongs. Specifically, there is an interest in carrying out investigations on the indoor environment through surveying existing Heating, Ventilation, Air Conditioning (HVAC) system operations in classrooms. Indoor air temperature and CO2 concentration in multiple lecture halls in Toronto, Canada were monitored; observations consistently show high indoor air temperature (overheating) and high CO2 concentration. One classroom is chosen as a representative case study for this paper. The results verify a strong correlation between the number of occupants and the increase in air temperature and CO2 concentration. Building Energy Simulation (BES) is used to investigate the causes of discomfort in the classroom, and to identify methods for regulating the temperature and CO2 concentration. This paper proposes retro-commissioning strategies that could be implemented in institutional buildings; specifically, the increase of outdoor airflow rate and the addition of occupancy-based pre-active HVAC system control. The proposed retrofit cases reduce the measured overheating in the classrooms by 2-3 °C (indoor temperature should be below 23 °C) and maintain CO2 concentration under 900 ppm (the CO2 threshold is 1000 ppm), showing promising improvements to a classroom’s thermal condition and indoor air quality.
... The generalization of findings to the entire Region is not possible due to the dearth of data for many low-income and lower-middle-income nations. High CO2 levels in a closed learning environment divert students' attention and make them queasy in classrooms (Chatzidiakou et al., 2015). A classroom study with a controlled environment found that students' learning status improved on different tests in a room with a good level of ventilation and decreased levels of CO2 (Haverinen-Shaughnessy & Shaughnessy, 2015). ...
The research aimed to determine the effects of Micro-Environmental Factors (MEFs) on students’ learning. Students’ learning was measured in controlled and uncontrolled MEFs within classroom. Researcher explored the effects of MEFs on students’ learning and find out the relationship between them. For this study, the experimental research design was used. In the first step, The Classroom Environmental Monitoring System (CEMS) was developed using (COTS) sensors to measure MEFs like temperature, CO2, humidity, and luminosity. In second step a test was conducted to evaluate students' learning. Data were collected by experiment in twelve (12) government and eighteen (18) private colleges of division Bahawalpur. Data analysis was performed in python using Logit, Probit Regression models, and Artificial Neural Network (ANN). The result of this study reveals that MEFs have impact on the students’ learning and both the variables are correlated. Henceforth, monitoring the MEFs during teaching learning process ultimately enhanced the learning of students.
... The relationship between IAQ conditions in enclosed spaces and the susceptibility of building occupants to sickness and disease transmission is supported by a long history of evidence [9][10][11][12][13]. For decades, indoor C02 concentration has been accepted as a proxy for indoor fresh air rate and found to negatively impact cognition at high indoor concentrations [14,15]. Recent studies have begun to identify correlations between poor IAQ and COVID-19 vulnerability and mortality as well [16][17][18][19]. ...
Transmission of airborne disease is a concern in many indoor spaces. Recent studies have identified correlations between poor indoor air quality (IAQ) and COVID-19 vulnerability and mortality. Studying the role building design and ventilation play in both the spread and mitigation of airborne viruses in high-density spaces is thus imperative. However, guidance for IAQ improvement and COVID-19 risk mitigation is general and insufficient for specific application in at-risk spaces like British Columbia’s (BC) patient settings and long-term care homes. What remains underdefined is a workflow for translating site specific data on indoor aerosol spread into actionable tools health officials can use towards building retrofit and intervention planning. The objective of this project was thus to develop a library of ‘digital twin’ models of at-risk indoor spaces that can provide accurate and rapid investigations of indoor air quality improvement measures using computation fluid dynamics (CFD) software. To calibrate these models, 41 repeated controlled experiments of aerosol dispersion and removal were conducted to assess the ventilation patterns of a 4-bed hospital room. From these experiments, a 3D CFD model of the room was created using the RhinoCFD modelling package, calibrated with measured IAQ sensor data, and validated against the results of the live study. This paper presents the methodology and in-progress results of this CFD modelling process.
... Opening a window can be an efficient way to remove hot indoor temperatures. On the other hand, good ventilation improves the thermal environment and helps remove indoor pollutants from a building (Chatzidiakou et al. 2015;Lipczynska et al. 2015). Performing this method will help improve thermal comfort and health. ...
Thermal comfort is linked to our health, well-being, and productivity. The thermal environment is one of the main factors that influence thermal comfort and, consequently, the productivity of occupants inside buildings. Meanwhile, behavioural adaptation is well known to be the most critical contributor to the adaptive thermal comfort model. This systematic review aims to provide evidence regarding indoor thermal comfort temperature and related behavioural adaptation. Studies published between 2010 and 2022 examining indoor thermal comfort temperature and behavioural adaptations were considered. In this review, the indoor thermal comfort temperature ranges from 15.0 to 33.8 °C. The thermal comfort temperature range varied depending on several factors, such as climatic features, ventilation mode, type of buildings, and age of the study population. Elderly and younger children have distinctive thermal acceptability. Clothing adjustment, fan usage, AC usage, and open window were the most common adaptive behaviour performed. Evidence shows that behavioural adaptations were also influenced by climatic features, ventilation mode, type of buildings, and age of the study population. Building designs should incorporate all factors that affect the thermal comfort of the occupants. Awareness of practical behavioural adaptations is crucial to ensure occupants' optimal thermal comfort.
... Most studies on interactions have been undertaken in schools or offices, and between IAQ and thermal quality. [104][105][106] For example, Chatzidiakou et al. 107 developed a model to demonstrate the relationship between indoor air temperature and CO 2 concentration. They found that a high CO 2 concentration (e.g. ...
Because of COVID-19, the indoor environmental quality (IEQ) in sports facilities has been a concern to environmental health practitioners. To develop an overall understanding of the available guidelines and standards and studies performed on IEQ in sports facilities, an extensive literature study was conducted, with the aim of identifying: (1) indicators that are being used to assess IEQ in different sports facilities; (2) indicators that are potentially interesting to be used to assess indoor air, in particular; (3) gaps in knowledge to determine whether sports facilities are safe, healthy and comfortable for people to stay and perform their activities. The outcome indicates that most current standards and previous investigations on IEQ in sports facilities mainly focused on dose-related indicators (such as ventilation rate), while building-related indicators (such as ventilation regime) and occupant-related indicators (such as IEQ preferences) were rarely considered. Little attention is given to the fact that ventilation systems may play an important role in the air quality of the location, and few investigations have been performed on the transmission of SARS-CoV-2. This study recommends more research into both occupant and building-related indicators as well as cross-modal effects between various IEQ factors for developing future standards on sports facilities.
... Recognizing that several factors related to IEQ can influence health and well-being of older adults, as a proof of concept, we decided to test our data collection platform by focusing on indoor thermal environment (i.e., temperature and humidity) and air quality because of their well-established influence on short-and long-term outcomes related to health and wellbeing, and availability of low-cost and easy-to-use smart sensors to measure them. Further, recognizing that there exist many indoor air pollutants with substantial impact on occupants' health and wellbeing, as a proof of concept, we selected CO 2 concentration because it is a measure of overall indoor air quality and adequacy of natural and/or mechanical ventilation (Batterman & Peng, 1995;Chatzidiakou et al., 2015;Scheff et al., 2000). Table 1 details the specific physiological variables and outcomes related to health and wellbeing that we aimed to collect. ...
Technology provides new opportunities to understand and optimize the relationship between the home indoor environmental quality and health outcomes in older adults. We aimed to establish proof-of-concept and feasibility of remote, real-time, high-frequency, and simultaneous monitoring of select environmental variables and outcomes related to health and wellbeing in older adults. Thirty-four participants (27 were female) with an average age (SD) of 81 years (±7.1) were recruited from community and supportive housing environments. Environmental sensors were installed in each home and participants were asked to use a wearable device on their finger and answer smartphone-based questionnaires on a daily basis. Further, a subgroup of participants were asked to complete tablet-based cognitive tests on a daily basis. Average compliance with the wearable (time worn properly/total time with device) was 81%. Participants responded to 69% of daily smartphone surveys and completed 80% of the prescribed cognitive tests. These results suggest that it is feasible to study the impact of the home thermal environment and air quality on biological rhythms, cognition, and other outcomes in older adults. However, the success of non-passive data collection elements may be contingent upon baseline cognition.
... For example, multilevel modelling was used to discuss the impact of behavioural and environmental factors on pollution levels. The study stated that the elimination of emission sources, increasing ventilation rates and adjusting the temperature depending on seasonal variations can help in controlling the Total Volatile Organic Compounds (TVOCs) level [21]. Also, the multi-criteria approach was used to investigate the influence of passive spaces on the environmental performance of buildings and optimization scenarios during the renovation process [22]. ...
... The average values of N 2 O concentration measured in laboratory are consistent with the typical atmospheric concentration of ~330 ppb [6] but slightly lower. The average values of CO 2 concentration are almost double compared to the typical outdoor CO 2 concentration ~400 ppm [45], but the measured values are consistent with the typical indoor CO 2 concentration [46]. In fact, in closed environments, the CO 2 levels strongly depend on the carbon dioxide emitted in human breath (~4-5 % of total exhalation) [47]. ...
We report on a gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) able to detect multiple gas species for environmental monitoring applications, by exploiting a Vernier effect-based quantum cascade laser as the excitation source. The device emission spectrum consists of ten separated emission clusters covering the range from 2100 up to 2250 cm⁻¹. Four clusters were selected to detect the absorption features of carbon monoxide (CO), nitrous oxide (N2O), carbon dioxide (CO2), and water vapor (H2O), respectively. The sensor was calibrated with certified concentrations of CO, N2O and CO2 in a wet nitrogen matrix. The H2O absorption feature was used to monitor the water vapor within the gas line during the calibration. Minimum detection limits of 6 ppb, 7 ppb, and 70 ppm were achieved for CO, N2O and CO2, respectively, at 100 ms of integration time. As proof of concept, the QEPAS sensor was tested by continuously sampling indoor laboratory air and monitoring the analytes concentrations.
... It is debated whether these associations exist because the higher indoor CO2 concentrations are correlated with higher levels of other indoor-generated pollutants which are the causative agents of the adverse effects (Mudarri 1997;Persily 1997). Yet, as suggested by Chatzidiakou et al. (2015), CO2 concentration can be used as a good proxy for overall IAQ, with the exception of traffic-related pollutants. Moreover, other studies have underlined the direct negative impacts of CO2 on occupants, in the range of concentrations typically found in buildings. ...
... To date, several studies investigated the association between CO 2 and other indoor pollutants to test if CO 2 is an overall indicator for IAQ (Branco et al., 2019;Ramalho et al., 2015;Chatzidiakou et al., 2015;Zhao et al., 2008;Szczurek et al., 2015;Batterman and Peng, 1995;Liang et al., 2020). All these studies unanimously have come to the conclusion that CO 2 is a good indicator of bio-effluents from human occupants, but it is a poor predictor of other indoor air pollutants, such as particulate matter (PM) and volatile organic compounds (VOCs) emitted from non-human sources. ...
Daycare centers (DCCs) are where infants and toddlers (0–4 years old) spend the most time besides their homes. Given their higher susceptibility to the effects of air pollutants, as compared to older children and adults, indoor air quality (IAQ) is regarded as an essential parameter to monitor in DCCs. Recent advances in IAQ monitoring technologies have enabled the deployment of low-cost air quality monitors (LCMs) and single sensors (LCSs) to continuously monitor various indoor environments, and their performance testing should also be performed in the intended indoor applications. To our knowledge, there is no study evaluating the application of LCMs/LCSs in DCCs scenarios yet.
Therefore, this study is aimed to assess the response of five types of LCMs (previously not tested) and five LCSs to typical DCCs emission activities in detecting multiple IAQ parameters, i.e., particulate matter, carbon dioxide, total volatile organic compounds, temperature, and relative humidity. These LCMs/LCSs were compared to outcomes from research-grade instruments (RGIs). All the experiments were performed in a climate chamber, where three kinds of typical activities (background; arts-and-crafts; cleaning; [in a total of 32 events]) were simulated by recruited subjects at two typical indoor climatic conditions (cool and dry [20 ± 1 °C & 40 ± 10%], warm and humid [26 ± 1 °C & 70 ± 5%]).
Results showed that tested LCMs had the ability to capture DCCs activities by simultaneously monitoring multiple IAQ parameters, and LCMs/LCSs revealed a strong correlation with RGIs in most events (R² values from 0.7 to 1), but, for some events, the magnitude of responses varied widely. Sensirion SCD41, an emerging CO2 sensor built on the photoacoustic sensing principle, had a more accurate performance than all tested NDIR-based CO2 sensors/monitors. In general, the study implies that the selection of LCMs/LCSs for a specific application of interest should be based on emission characteristics and space conditions.
... A wide range of techniques exists to evaluate ventilation and indoor air quality. For single zones buildings, like shelters, the CO2 indoor concentration technique is widely adopted (Chatzidiakou et al., 2015;Batterman, 2017;ASHRAE, 2019). The use of CO2 as a tracer contaminant has been suggested from existing literature (Persily et al., 1997;Parent, et al., 1998;Gids de et al., 2010;Batterman, 2017). ...
In built environments, thermal comfort has a significant influence on human health, safety, and productivity. Its importance is more valued in thermally stressed environments that are characterized by extreme climatic conditions, where considerable amounts of energy are consumed to achieve indoor thermal comfort. The worldwide increased demand for energy and the environmental consequences of such a trend highlights the importance of this topic.
Energy and Environment are global and interrelated issues that are unconstrained by political borders. Hence, countries of the whole world must cooperate in order to find solutions to ensure the sustainability of natural resources for future generations. This reveals the importance of scientific gatherings like the 2nd International Conference of Comfort At The Extremes, [CATE’21], which was organised by the College of Engineering, Sultan Qaboos University, on 24th-26th October 2021. The conference provided a forum for scientists and researchers from different countries of the world and strengthens collaboration between them in the field of thermal comfort in thermally stressed environments. Researchers from more than 19 countries contributed to CATE’21 reflecting global interest in the subject.
These countries are from the MENA region (The Middle East and North Africa), the UK, Europe, Russia, Asia, the USA, and South America.
The conference attracted a good number of articles. From 83 submitted abstracts, 59 had been accepted with a retention of 71%. The accepted abstracts formed 44 papers, 15 abstracts, and 8 keynote speakers. Moreover, 8 of the papers had been further modified to be published in a special issue in The Journal of Engineering Research (TJER), published by the College of Engineering at Sultan Qaboos University (https://journals.squ.edu.om/index.php/tjer/issue/view/294/78).
... A wide range of techniques exists to evaluate ventilation and indoor air quality. For single zones buildings, like shelters, the CO2 indoor concentration technique is widely adopted (Chatzidiakou et al., 2015;Batterman, 2017;ASHRAE, 2019). The use of CO2 as a tracer contaminant has been suggested from existing literature (Persily et al., 1997;Parent, et al., 1998;Gids de et al., 2010;Batterman, 2017). ...
... CO 2 is often monitored as a proxy for occupancy in rooms [13,14]. People produce CO 2 proportionally to their body mass and metabolic rate. ...
CO2 is customarily used to control ventilation as it is a proxy for bio-effluents and pollutants related to the presence and activity of people in the room. However, CO2 could not be a satisfactory indicator for pollutants that do not have a metabolic origin, i.e., emissions from building materials or emissions from traffic. A methodology to select pollutants besides or instead of CO2 is presented in this article. This methodology sets to study (i) the suitable location to measure air pollutants and (ii) which parameters to measure. The answers to these two questions are based on correlation analysis between pollutants and indoor/outdoor ratios.
Measurements of CO2, air temperature, relative humidity, formaldehyde, and particulate matter have been taken in an office, an industrial kitchen, and a gym and are used to show how to apply the methodology. Correlations were studied in detrended (pre-whitened) time series. Studying correlations in detrended time series via cross-correlation functions is recommended because correlation coefficients may be overestimated because of the trends in the time series. In contrast to Pearson's correlation coefficient, the cross-correlation function studies the correlation between pollutants concurrently (as Pearson) but also at different time lags.
From the measurements we can conclude on the need to measure at least one parameter representing: 1) pollutants related to human activities 2) pollutants that infiltrate from processes like combustion or traffic outdoors, 3) pollutants related to combustion indoors, 4) pollutants related to degassing from building materials, 5) pollutants related to other “non-combustion-related activities” indoors and moisture loads.
https://authors.elsevier.com/a/1eEtu1HudN4EEL
... Las aulas escolares al ser espacios que albergan muchas personas por altos periodos de tiempo han sido estudiadas para tener óptimas condiciones de ventilación a partir del análisis del CO2 como medida relativa de ventilación, según publico la escuela de salud pública de Harvard [18] y aplicado por el Consejo Superior de Investigaciones Científicas para garantizar la adecuada ventilación en las aulas escolares de España [23], entre otras recomendaciones [24], [25]. Estudios previos sobre las concentraciones de CO2 y la calidad del aire para la actividad de la educación ya han sido estudiados previamente, independientemente de la nueva contingencia por el COVID-19 [26]- [29], con guías de implementación como la publicada por la Federación europea de calefacción, ventilación y aire acondicionado [30]. ...
The global pandemic due to the COVID-19 disease has led to the study of school classrooms as possible vectors of contagion. The CO2 has been established with an easily captured indicator to determine the adequate ventilation of these spaces. However, continuous ventilation can cause a lack of comfort in students and therefore be detrimental to their cognitive development. Therefore, it is necessary to study an optimal way to ventilate and the objective of this study is to evaluate the CO2 of a school classroom to optimize natural ventilation, minimizing the loss of comfort and thus reducing the risk factor for COVID-19. CO2 and air flow measurements were carried out in three study days in a secondary school in Madrid in which tests were carried out on the closing and opening of doors and windows to determine the opening time necessary to reach an optimal level of CO2.
Resumen
La pandemia mundial por la enfermedad del COVID-19 ha llevado a estudiar las aulas escolares como posibles vectores de contagio. Se ha establecido el CO2 con un indicador de fácil captura para determinar la adecuada ventilación de estos espacios. Sin embargo, la ventilación continua puede ocasionar falta de confort en los estudiantes y por lo tanto ir en detrimento de su desarrollo cognitivo. Por lo tanto, es necesario estudiar una forma óptima de ventilar y el objetivo del presente estudio es evaluar el CO2 de un aula escolar en aras de optimizar la ventilación natural minimizando la pérdida de confort y así disminuir el factor de riesgo ante el COVID-19. Se realizaron mediciones de CO2 y caudal del aire en tres jornadas de estudio en un colegio de secundaria en Madrid en el cual se realizaron pruebas de cierre y apertura de puertas y ventanas para determinar el tiempo de apertura necesario para llegar a un nivel óptimo de CO2.
... Indoor air quality (IAQ) in college classrooms has been recognized as a major factor that affects student health (Aziz et al. 2015;Cichowicz et al. 2015;Stabile et al. 2017) and academic performance (Brink et al. ; Twardella et al. 2012). The IAQ is primarily indicated by indoor carbon dioxide (CO2) and particulate matter (PM) concentrations (Chatzidiakou et al. 2015;Liang et al.). In buildings, CO2 concentration is closely linked with occupants' physiological responses (Allen et al. 2016;Zhang et al. 2016), and high CO2 concentration greatly reduce both cognitive performance and learning efficiency (Kenichi et al. 2018). ...
In China, natural ventilation is a common way of improving indoor air quality (IAQ) in college classrooms. However, until now, the effects of both manual airing strategies and architectural factors on IAQ in classrooms have not been well explored. The present work aimed to investigate the effect of manual airing strategies, such as opening doors and opening exterior or interior windows, on the concentrations of both carbon dioxide (CO2) and fine particulate matter (PM2.5) in classrooms using field measurements. Through simulation, the effects of floor level, room orientation and the height of interior windows on CO2 concentration were also analysed. The results of this study revealed that (1) simultaneously opening doors and exterior windows or opening the doors alone could effectively reduce the indoor CO2 concentration, but the same effect could not be achieved by opening interior windows only; (2) the indoor PM2.5 concentration was primarily affected by the level of outdoor PM2.5, and it may exceed the recommended limit by 33% when the outdoor pollution level is high, even with closed doors and windows; and (3) in winter, both floor level and classroom orientation exerted a significant influence on the indoor CO2 concentration, but the height of interior windows had no effect.
... Kalimeri et al. [6] obtained similar results in Greece. CO 2 is considered an indicator of bioefluents in high-density occupied spaces [41,42] and as a reference for IAQ levels but not as a direct indicator of air pollutants [1]. Other publications use CO 2 level as a primary indicator of the IAQ, as Clements-Croome et al. [43] and Almeida et al. [44]. ...
Indoor air quality in schools has a direct impact on the performance and wellbeing of students. In 2020, the health emergency required the reconsideration of ventilation conditions in indoor spaces, especially for educational buildings. This paper advances previous investigations to identify affordable, sustainable, and healthy designs for the refurbishment and new construction of schools, analysing the design parameters of the buildings and the indoor air quality in a representative sample of schools in the Mediterranean climate. The set of schools represents the regional composition regarding ages, daily scholar schedules and building designs. This study evaluates indoor CO2, TVOCs, PM 2.5 and PM 10, concentration profiles regarding indoor temperature, relative humidity, and occupation rates to identify adequate natural ventilation strategies. The results show a wide dispersion in CO2 concentrations, ranging between 4110 and 5366 ppm (peak values), TVOC mean concentration varies from 206.99 μg/m³ to 589.71 μg/m³ and particulate matter fractions ranging between 1.14 and 15.6 μg/m³ for PM 2.5 and 2.04 and 34.86 μg/m³ for PM 10 during the occupancy period. Concentrations are related to the effect of ventilation actions, the occupation rates and the metabolism of occupants. The combination of values shows how natural ventilation designs can assure adequate indoor air quality within comfort conditions under these mild climate conditions.
... Indoor air quality (IAQ) in college classrooms has been recognised as a major factor that affects student health (Aziz et al. 2015;Cichowicz et al. 2015;Stabile et al. 2017) and academic performance (Brink et al. 2021;Twardella et al. 2012). The IAQ is primarily indicated by indoor carbon dioxide (CO 2 ) and particulate matter (PM) concentrations (Chatzidiakou et al. 2015;Liang et al. 2020). In buildings, CO 2 concentration is closely linked with occupants' physiological responses (Allen et al. 2016;Zhang et al. 2016), and high CO 2 concentration greatly reduces both cognitive performance and learning efficiency (Kenichi et al. 2018). ...
In China, natural ventilation is a common way of improving indoor air quality (IAQ) in college classrooms. However, until now, the effects of both manual airing strategies and architectural factors on IAQ in classrooms have not been well explored. The present work aimed to investigate the effect of manual airing strategies, such as opening doors and opening exterior or interior windows, on the concentrations of both carbon dioxide (CO2) and fine particulate matter (PM2.5) in classrooms using field measurements. Through simulation, the effects of floor level, room orientation and the height of interior windows on CO2 concentration were also analysed. The results of this study revealed that (1) simultaneously opening doors and exterior windows or opening the doors alone could effectively reduce the indoor CO2 concentration, but the same effect could not be achieved by opening interior windows only; (2) the indoor PM2.5 concentration was primarily affected by the level of outdoor PM2.5, and it may exceed the recommended limit by 33% when the outdoor pollution level is high, even with closed doors and windows; and (3) in winter, both floor level and classroom orientation exerted a significant influence on the indoor CO2 concentration, but the height of interior windows had no effect.
... Hence, we also study the impact of energy-saving strategies on air-exchange rates and the concentration of indoor CO2, which is a measure of overall indoor air quality [41,42]. ...
Local and state governments find it challenging to adopt aggressive residential building codes that require energy-efficiency upgrades beyond those with a reasonable payback. Thus, economic considerations inhibit the progress towards a more energy-efficient housing stock and often account for direct utility savings. A widely discussed solution is to look beyond energy costs and consider other impacts of energy-saving strategies that affect their financial attractiveness. In this paper, we examine the case of a public housing project in Phoenix, AZ, using several tools to calculate different economic, environmental, and health metrics associated with the three levels of energy efficiency. Our results show that while the payback calculated from direct energy costs may not be attractive, we should consider other savings. We demonstrate that avoided health and climate costs could total around 40% of the direct utility savings. In addition, we quantify how energy-saving strategies can cool the neighborhood, make buildings more resilient to heat, improve indoor air quality, and reduce the transmission of airborne disease. These benefits could be translated to avoid costs in the future.
... Therefore, CO2 is considered a good IAQ indicator, which shows the relationship between ventilation rate and occupancy. In addition, CO2 has been associated with the presence of other pollutants [4,8]. The presence of pollutants like bioaerosols, Particle Matter (PM), or Total Volatile Organic Compounds (TVOCs) [9] is harmful to a pupil's health and productivity [10][11][12]. ...
This paper describes the implementation of a series of ventilation strategies in a nursery and primary school from September 2020, when the government decided to resume the students’ face-to-face activity in the middle of a COVID scenario. Air quality and hygrothermal comfort conditions were analysed before the pandemic and compared for different ventilation configurations in a post-COVID scenario. Ventilation strategies included the protocols issued by the Public Administration, while others were developed based on the typological configuration and use of the school. Results revealed that it is advisable to implement certain strategies that reduce the risk of infection among the occupants of the spaces, without a significant decrease in hygrothermal comfort. Given the importance of maintaining better IAQ in the future within classrooms, and regarding the pre-COVID situation, these strategies may be extended beyond this pandemic period, through a simple protocol and necessary didactic package to be assumed by both teachers and students of the centre.
... [6][7][8] It is debated whether these associations exist because the higher indoor CO 2 concentrations are correlated with higher levels of other indoor-generated pollutants which are the causative agents of the adverse effects. 9,10 Yet, as suggested by Chatzidiakou et al., 11 CO 2 concentration can be used as a useful proxy for occupant-related contaminants. ...
The Covid-19 outbreak has resulted in new patterns of home occupancy, the implications of which for indoor air quality (IAQ) and energy use are not well-known. In this context, the present study investigates 8 flats in London to uncover if during a lockdown, (a) IAQ in the monitored flats deteriorated, (b) the patterns of window operation by occupants changed, and (c) more effective ventilation patterns could enhance IAQ without significant increases in heating energy demand. To this end, one-year’s worth of monitored data on indoor and outdoor environment along with occupant use of windows has been used to analyse the impact of lockdown on IAQ and infer probabilistic models of window operation behaviour. Moreover, using on-site CO 2 data, monitored occupancy and operation of windows, the team has calibrated a thermal performance model of one of the flats to investigate the implications of alternative ventilation strategies. The results suggest that despite the extended occupancy during lockdown, occupants relied less on natural ventilation, which led to an increase of median CO 2 concentration by up to 300 ppm. However, simple natural ventilation patterns or use of mechanical ventilation with heat recovery proves to be very effective to maintain acceptable IAQ.
Practical application: This study provides evidence on the deterioration of indoor air quality resulting from homeworking during imposed lockdowns. It also tests and recommends specific ventilation strategies to maintain acceptable indoor air quality at home despite the extended occupancy hours.
... Ces conclusions valident celles de Fischer (2001) et de Schneider (2002). En effet, la qualité de l'air et la température sont des facteurs intimement liés au taux d'absentéisme (Rosen et Richardson, 1999), à la congestion nasale et à l'asthme (Turunen et coll., 2014 ;Chatzidiakou, Mumovic et Summerfield, 2015), ainsi qu'à d'autres enjeux de santé, en lien avec la forte densité des élèves occupant une même pièce et de l'hypersensibilité de certains aux températures élevées (Zomorodian, Tahsildoost et Hafezi, 2016 ...
Les écoles au Québec font face à un contexte de détérioration des infrastructures et du mobilier qui atteint des seuils allant bien au-delà de ce qui est tolérable. L’état des lieux soulève des questions en matière d’habitabilité et fait plus spécifiquement surgir la question du confort des élèves. En effet, plusieurs recherches en pédagogie soulignent que le confort représente une des fonctions essentielles auxquelles la classe doit pouvoir répondre afin de soutenir l’apprentissage des élèves. À ce jour, le confort en milieu scolaire a surtout été abordé à partir de données objectives de nature ergonomique et architecturale. Or, les avancées en recherche suggèrent de l’envisager sous l’angle de l’expérience en raison des facteurs subjectifs qui le définissent.
Ce mémoire vise à comprendre comment l’expérience de confort est perçue, vécue et imaginée par les élèves et les enseignants, à traduire ces facteurs subjectifs en critères de design et en recommandations, de même qu’à identifier son apport à l’enrichissement de l’expérience éducative. Il aborde ces questions dans 19 écoles primaires du Québec à partir de données du contexte matériel, spatial, ainsi que d’enquêtes menées auprès des élèves et des enseignants.
Les résultats montrent que l’expérience de confort en contexte d’apprentissage est viscéralement contextuelle et subjective. Elle s’articule autour de treize indicateurs interreliés qui s’inscrivent dans quatre dimensions. En classe, le confort passe par un environnement calme et silencieux qui évite les stimuli inutiles, offre une cohérence visuelle, une fluidité de circulation, l’accès à des zones dédiées, ainsi qu’à des espaces personnels pour les élèves. Afin de stimuler le mouvement et l’autonomie des élèves, il ressort que l’environnement d’apprentissage doit aussi préconiser l'intégration d'une diversité de mobilier. Cette offre doit toutefois être rationalisée en regard des préoccupations ergonomiques. D’autres variables sont aussi en cause. Parmi celles-ci, les assises et surfaces de travail, devraient être ajustables spacieuses, mobiles, légères, silencieuses, personnalisables, réparables, nettoyables, durables, stables et simple à entreposer. Les sièges et les dossiers devraient privilégier des matériaux souples et des formes organiques.
Enfin, selon les enseignants, le confort serait susceptible d’améliorer l’expérience éducative, notamment en matière de concentration, de motivation et de confiance en soi.
... In spite of this, neither the public nor private administration has focused special attention on the IAQ of schools, and more surprisingly, it has also been neglected by the educational community and parents' associations. CO 2 is a good bio-effluents indicator, and it could be correlated with the ventilation of a room, therefore, its concentration rate is used as the main indicator of IAQ [15] and to determine the ventilation rate in occupied spaces [16] such as schools. However, if the levels of pollution are higher outside than indoors, CO 2 does not indicate indoor pollutants with health risk [17]. ...
Research studies have shown the potential effects of indoor environmental quality (IEQ) on pupils’ health and academic performance. The COVID-19 pandemic has prompted renewed interest in the assessment of deficient indoor air quality (IAQ) conditions in schools and has become a priority over achieving adequate comfort conditions. Scientific studies confirm aerosols as one of the transmission routes of SARS-CoV-2 so that the possibility of airborne transmission increases in indoor environments with high occupancy, such as classrooms. As a result, international protocols and guidelines have established a requirement for educational buildings to over-ventilate with a fresh outdoor air supply. The main object of this work is to analyse the effects of the COVID-19 pandemic on thermal comfort and indoor air quality, in winter, in two classrooms of southern Spain. Thus, onsite measurements of environmental variables were conducted before and during the pandemic. Both classrooms have mechanical ventilation systems as they are within a recently built primary school (2018). Results shows a decrease of 300 ppm in CO2 weekly average values during the pandemic, when hybrid ventilation is used, and a decrease of 400 ppm when schools are naturally ventilated during all teaching hours. However, the analysis of standards shows that over 60% of hours are thermal discomfort conditions.
... 1. Selected schools are naturally ventilated since windows are the main source of ventilation in most schools in the UK. Furthermore, variations in temperature, relative humidity and indoor pollutants from mechanical ventilation and air-conditioning systems [50,51,53] can impact children's perception of IEQ. 2. Schools were selected in quiet areas with a considerable distance to the main road to not restrict window operation due to high background noise level as recommended by Building Bulletin 93: Acoustic Design of Schools to facilitate natural ventilation [54]. Selected schools have the regional Road Noise, LAeq 16h, less than 55 dB according to England Noise Map Viewer [55]. ...
Indoor Environment Quality (IEQ) is grouped into four main categories: thermal comfort, indoor air quality (IAQ), visual and acoustic comfort. Individual aspects of IEQ are investigated to examine their impact on children's overall comfort in primary schools in the UK. This study has surveyed 805 children in 32 naturally ventilated classrooms during non-heating and heating seasons. This study has calculated the proportion of comfort votes by individual aspects of IEQ, predicted comfort votes by multilinear regression model and estimated the probability of having uncomfortable votes by binary logistic regression.
Results of this study highlight that the proportion of uncomfortable votes should be kept below 10%. The developed multilinear model suggests that for a unit change in Air Sensation Votes (ASVs) and operative temperatures (Top), comfort votes change by 0.28 and 0.12, respectively. Developed multilinear and logistic regression models show that ASVs have a more significant impact on overall comfort than Top. To achieve acceptable comfortable votes and keep the probability of having uncomfortable votes below 10%, ASVs and Top should be kept within these limits: [ASV = very fresh and Top = 19–27 °C], [ASV = fresh and Top = 19–24 °C], and [ASV = OK and Top = 19–22 °C]. The ranges suggest that better perception of IAQ makes up for higher temperatures. It is advised to maintain individual aspects of IEQ, however, dissatisfaction with one aspect of IEQ does not necessarily result in overall discomfort unless that aspect is extremely unacceptable. Investigating the most influential factors on occupants’ comfort suggests which building controls should be prioritized for designers.
... 2) Buildings were selected in quiet areas to not restrict window operation due to high background noise level, as supported in [67,68]. 3) Buildings were selected in low-polluted areas to not restrict window operation due to high pollution level, as supported in [15,16,68]. 4) Buildings were selected with different architectural features as different buildings provide different potentials for practising adaptive behaviours (ABs), Table 1. 5) Schools were selected among both renovated and existing buildings because they should comply with different IAQ standard. ...
Indoor Air Quality (IAQ) is affected by Context, Occupant and Building (COB) related factors. This paper evaluates IAQ as a function of occupant-related factors including occupants’ Adaptive Behaviours (ABs), occupancy patterns, occupant’s CO2 generation rates and occupancy density. This study observed occupant-related factors of 805 children in 29 naturally-ventilated (NV) classrooms in UK primary schools during Non-Heating and Heating seasons.
Occupant-related factors affecting IAQ include occupants’ adaptive behaviours, occupancy patterns, occupants’ CO2 generation rate and occupancy densities. Results of this study suggest that a classroom with high potentials for natural ventilation does not necessarily provide adequate IAQ, however, occupants’ good practice of ABs is also required. Average occupancy densities to have CO2 levels of 1000±50 ppm are suggested to be 2.3±0.05m2/p and 7.6±0.25 m3/p. These values correspond to the classroom area of 62.1±1.35 m2 and volume of 205.2±6.75 m3 with a height of 3.3 m. Mean CO2 level is maintained below 900 ppm when all occupant-related factors are in the favour of IAQ, however, it exceeds 1300 ppm when none of the occupant-related factors are in favour of IAQ.
It is shown that 17% of CO2 variations are explained by open area (m2), 14% by occupants’ generation rates (cm3/s) and 11% by occupancy density (m3/p). IAQ is mostly affected by occupants’ adaptive behaviours than other occupant-related factors in naturally-ventilated classrooms.
... Normally, the indoor CO 2 concentration is from 350 to 2500 ppm, and low-level CO 2 exposure is not a direct factor to health effect [2,3]. Because the source of indoor CO 2 is mainly from human metabolism for the residential buildings [4], the indoor CO 2 concentration was considered as a good proxy of bioeffluents [5,6]. Many scientific papers indicated that there was an association between indoor CO 2 concentration and sick building symptoms (SBS), cognitive performance and physiological responses [7][8][9]. ...
This paper summarizes current literature evidence on the associations of indoor carbon dioxide (CO2) with sleep quality and other human responses at dorms, bedrooms or other sleeping environments. Published literature was identified by searching Web of Science and Google Scholar, using the following keywords including carbon dioxide, sleep quality, ventilation rate, indoor air quality, and health effect. From selected studies, detailed findings were summarized based on subjective assessments and objective measurements. The collected data were then tabulated to observe the associations of CO2 concentration with sleep quality and other human responses. Furthermore, the potential confounding of researches was discussed. The results of the reviewed studies show that there was a tendency that lower CO2 concentration improved sleep quality. Given the findings of this summary, effects of indoor CO2 concentration on sleep quality are worthy for further study to elaborate the dose-response relationship between CO2 concentration and human responses during sleep and “no-effect” threshold of CO2 concentration for good sleeping environment requires further research.
... For many years, most of these papers proposed a simplified evaluation of the indoor air quality just considering the CO 2 concentrations and thermal comfort as main parameters; nonetheless, their negative effects can be merely restricted to students' vigilance and cognitive performances (Allen et al., 2016;Jiang et al., 2018;Mendell and Heath, 2005;Schweiker et al., 2018). Moreover, European standards, providing guidelines on ventilation rates, still adopt the CO 2 concentration as main design parameter (European Committee for Standardisation, 2008) since it is unanimously considered as a good proxy of the IAQ (Chatzidiakou et al., 2015;Satish et al., 2012). This approach is not adequate from a scientific point of view since the CO 2 behaviour (i.e. ...
Indoor school gyms are environments characterized by high concentrations of different airborne particulate and gaseous pollutants. In particular, like other naturally-ventilated school environments, in addition to indoor pollutants children can be exposed to sub-micron particles and gaseous pollutants emitted by outdoor sources and penetrating the building envelope; moreover, high concentrations of super-micron particles can be reached due to the resuspension phenomena related to the physical activity performed therein. The present paper aims to evaluate the effect of different ventilation methods (natural ventilation, manual airing) and the use of air purifiers in reducing the indoor concentrations of different airborne particles and gaseous pollutants in school gyms. To this end, an experimental campaign was performed in two naturally-ventilated school gyms in Barcelona (Spain) of different volumes and different distance to major urban roads. Indoor and outdoor measurements of particle number, black carbon and PM1-10 concentrations were performed as well as indoor measurements of CO2 and NO2 concentrations. The study revealed that the use of air purifiers with windows kept closed (natural ventilation) can lead to a significant reduction in terms of indoor-to-outdoor concentration ratios. In the smaller gym (air changes per hour of the purifiers, ACH, equal to 9.2 h-1) the I/O ratios were reduced by 93% and 95% in terms of particle number and PM1-10, respectively; whereas in the larger school gym (ACH = 1.7 h-1) the corresponding reductions were 70% and 84%. For manual airing scenarios, the effect of the air purifiers on outdoor-generated sub-micron particles is reduced; in particular, for low ACH values (i.e. ACH = 1.7 h-1), the reduction is quite negligible (6%).
The predicted and measured carbon dioxide (CO2) emitted by human respiration into an occupied space has been used as an indicator for controlling buildings' ventilation rates. However, this application assumes a constant emission rate for the entire population. Conversely, new knowledge has shown that this variable depends on the number of people in the room and their sex, diet, height, and above all, body mass and metabolic rate. This paper applies the latter model and a previously used sampling approach to identify the variability of CO2 emission rates and excess CO2 concentrations in school classrooms in Chile, and compares them with those in the USA. This time, we collected data from local sources and public databases to model an evidence-based average classroom of 29 students-15 men and 14 women-following the Chilean regulations and the ASHRAE 62.1 and ASHRAE 241 standards for ventilation. Then, using Python and a Monte Carlo sampling approach, we calculated the emission rates for the local population in the classrooms of children between 5 and 18 years old. Results show that the mean body weights of the USA and Chilean child populations are statistically different, but the excess CO2 concentrations can vary by only 4% between demographics. The difference in excess CO2 concentrations between countries reflects their differences in occupancy densities. Finally, there is a significant difference in excess CO2 concentrations for the two standards but little difference between countries for the same standard.
Plug-in fragrance diffusers are one of myriad volatile organic compound-containing consumer products that are commonly found in homes. The perturbing effects of using a commercial diffuser indoors were evaluated using a study group of 60 homes in Ashford, UK. Air samples were taken over 3 day periods with the diffuser switched on and in a parallel set of control homes where it was off. At least four measurements were taken in each home using vacuum-release into 6 L silica-coated canisters and with >40 VOCs quantified using gas chromatography with FID and MS (GC-FID-QMS). Occupants self-reported their use of other VOC-containing products. The variability between homes was very high with the 72 hour sum of all measured VOCs ranging between 30 and >5000 μg m-3, dominated by n/i-butane, propane, and ethanol. For those homes in the lowest quartile of air exchange rate (identified using CO2 and TVOC sensors as proxies) the use of a diffuser led to a statistically significant increase (p-value < 0.02) in the summed concentration of detectable fragrance VOCs and some individual species, e.g. alpha pinene rising from a median of 9 μg m-3 to 15 μg m-3 (p-value < 0.02). The observed increments were broadly in line with model-calculated estimates based on fragrance weight loss, room sizes and air exchange rates.
Occupants’ use of windows can influence the building energy demand, thermal conditions and indoor air quality. Researchers have made substantial efforts to develop probabilistic models to predict the window open/closed state. However, the hierarchical data structure and the heterogeneity in occupant behaviour have been generally neglected in previous modelling efforts. Multilevel modelling can provide an appropriate framework to handle this type of data structure and variability, but this method has rarely been used in the field. This study investigated room- and apartment-level variations in the effects of outdoor environmental variables on the window open state in low-energy apartment buildings in the UK using a multilevel modelling approach. The results showed that the room-level, rather than apartment-level, variation was statistically significant. Meanwhile, the room type (i.e., living room or bedroom) did not significantly affect the relationship between outdoor environmental variables and the window open state. The strength of this study is that the modelling accounted for the hierarchical structure of the data by simultaneously considering room-and apartment- level behavioural variations. By quantifying the significant diversity of occupant behaviour in the natural ventilation of residences, future research can more accurately estimate the variation in building energy and indoor air quality impacts.
Utilizar espaços internos é inerente aos seres humanos, que passam, em média, a maior parte do tempo nesses locais. As salas de aula são alvo de crescente preocupação científica sobretudo quando submetidas a baixas taxas de renovação de ar. O dióxido de carbono é, tradicionalmente, considerado um indicador da qualidade do ar interior (QAI). No ambiente escolar, altas concentrações desse gás estão relacionadas à diminuição da cognição e do desempenho dos estudantes. O objetivo deste estudo foi fazer uma revisão da literatura de artigos que tratam da QAI e dos níveis de CO2 em salas de aula com ventilação natural. A metodologia adotada foi a Revisão Sistemática da Literatura (RSL). Realizou-se uma seleção de artigos junto ao Portal de Periódicos da Capes e ScienceDirect, que resultou na inclusão e análise de 34 artigos. Como resultados, observou-se que, frequentemente, as salas de aula operam com concentrações médias de CO2 superiores a 1000 ppm, bem como, uma significativa relação pico-média, o que indica a baixa eficiência da renovação de ar. Os trabalhos indicaram que a ação dos usuários, por meio do julgamento subjetivo e do comportamento adaptativo, influenciou o aumento dos níveis desse gás, assim como a abertura de janelas e portas nos intervalos de aula não foi suficiente para manter a qualidade recomendada. Essa temática ganhou relevância devido à pandemia do COVID-19 em 2020, em que ficou evidente a necessidade de estratégias adequadas para a dispersão dos contaminantes.
Healthy building design is an emerging field of architecture and building engineering. Indoor air quality (IAQ) is an inevitable factor that should be considered in healthy building design due to its demonstrated links with human health and well-being. This paper proposes to integrate IAQ prediction into healthy building design by developing a simulation toolbox, termed i-IAQ, using MATLAB App Designer. Within the i-IAQ, users can input information of building layout and wall-openings and select air pollutant sources from the database. As an output, the toolbox simulates indoor levels of carbon dioxide (CO2), total volatile organic compounds (TVOC), inhalable particles (PM10), fine particles (PM2.5), nitrogen dioxide (NO2), and ozone (O3) during the occupied periods. Based on the simulation results, the toolbox also offers diagnosis and recommendations to improve the design. The accuracy of the toolbox was validated by a case study in an apartment where physical measurements of air pollutants took place. The results suggest that designers can integrate the i-IAQ toolbox in building design, so that the potential IAQ issues can be resolved at the early design stage at a low cost. The paper outcomes have the potential to pave a way towards more holistic healthy building design, and novel and cost-effective IAQ management.
Healthy indoor environments influence the comfort, health and wellbeing of the occupants. Monitoring the indoor temperature, relative humidity and CO2 levels in primary schools during the COVID-19 pandemic was mandated by a local authority in Scotland. The aim was to investigate the comfort and safety of the teachers and their pupils. This paper presents the measurements of indoor climate in 20 classrooms in four different primary schools in Scotland. The schools were of different architypes. The classrooms were of different sizes, orientations and occupancy, and had different ventilation systems. Ventilation was achieved either by manually opening the windows, or by a mechanical ventilation system. Indoor air temperature, relative humidity and carbon dioxide (CO2) concentrations were continuously monitored for one week during the heating season 2020/21. Occupancy and opening of the windows were logged in by the teachers. The ventilation rates in the classrooms were estimated by measuring the CO2 concentrations. On the 20 classrooms of the study, data of 19 were analysed. The results show that four of the five mechanically ventilated classrooms performed better than natural ventilation, which indicates that opening the windows depended on the customs and habits. Classrooms in naturally ventilated Victorian buildings have the worst average ventilation rate (4.38 L/s per person) compared to the other classrooms (5.8 L/s per person for the more recent naturally ventilated ones, and 6.08 L/s per person for the mechanically ventilated ones). The results of this preliminary study will be used as the basis to find ways to ensure adequate ventilation in natural ventilated classrooms.
Emerging data indicates that incumbent mechanical/physio-chemical air handling systems inadequately address common indoor air quality (IAQ) problems, including elevated CO2 levels and volatile organic compounds (VOCs), with compounding negative impacts to human health. Preliminary research suggests that active plant-based systems may synthetically address these challenges. However, in order to design system performance parameters, the significance of species selection and biogeochemical mechanisms of growth media design need further characterization towards an effective bioremediative interface with air handling systems. Here, through three different species across three different growth media designs, we investigate trade-offs between CO2 sequestration through photosynthesis and CO2 production by metabolically active root-zones (that may remediate VOCs). Across the species, hydroponic media produced 61% greater photosynthetic leaf area compared to organic media which produced 66% more root biomass. CO2 concentration changes driven by differing plant and growth media (organic vs. hydroponic) treatments were measured within a semi-sealed chamber. Repeated estimations of net CO2 concentrations throughout plant development revealed decreasing influxes of CO2 within the chamber over time, indicating evolving photosynthesis/respiration balances. Multivariate analysis indicates growth media design, through impacts to water availability, air flow rates and plant development, was a more significant driver of bioremediation performance metrics than species selection.
Since the COVID-19 pandemic, the ventilation of school buildings has attracted considerable attention from the general public and researchers. However, guidance to assess the ventilation performance in classrooms, especially during a pandemic, is still lacking. Therefore, aiming to fill this gap, this study conducted a full-scale laboratory study to monitor the CO 2 concentrations at 18 locations in a classroom setting under four different ventilation regimes. Additionally, a field study was carried out in two Dutch secondary schools to monitor the CO 2 concentrations in the real classrooms with different ventilation regimes. Both the laboratory and field study findings showed that CO 2 concentrations varied a lot between different locations in the same room, especially under natural ventilation conditions. The outcome demonstrates the need of monitoring the CO 2 concentration at more than one location in a classroom. Moreover, the monitored CO 2 concentration patterns for different ventilation regimes were used to determine the most representative location for CO 2 monitoring in classrooms. For naturally ventilated classrooms, the location on the wall opposite to windows and the location on the front wall (nearby the teacher) were recommended. For mechanically ventilated classrooms, one measurement location seemed enough because CO 2 was well-mixed under this ventilation regime.
Occupant behaviour (OB) is one of the main causes of the energy performance gap between buildings’ performance prediction versus reality, since, due to its uncertainty and unpredictability, it is often oversimplified in the building performance simulation (BPS). Hence, previous studies developed OB models, mainly in the residential and office contexts, in order to predict and represent human behaviour in BPS. Yet, school buildings are different from other typologies due to contextual factors (e.g., occupants’ age, different daily timetables and group rules) and are in a unique position to promote energy efficiency for tomorrow’s citizens. Assessing OB in schools can lead to an improvement of the indoor environment, especially in naturally ventilated buildings, where window operation behaviour directly impacts on the air change rates and, consequently, on the indoor air quality. This study addresses the knowledge gap on OB modelling for naturally ventilated (NV) and mixed-mode (MM) school buildings. The reviewed papers were organized in three main themes, namely (i) OB models for BPS of NV and MM buildings, (ii) OB research studies in NV and MM school buildings and (iii) potential changes on OB in school buildings due to the COVID-19 pandemic. The analysis focused on three phases of the OB modelling framework: data collection (pre-processing), model development (processing) and model implementation (post-processing). Important research gaps are identified, such as the reduced number of studies that cover the three phases of the modelling framework within the school buildings context and the need to better investigate the teachers’ behaviour and collective actions as important OB drivers in classrooms. Future research topics are also identified, such as which are the potential changes on actions’ drivers due to the COVID-19 pandemic in NV classrooms and to what extent they will be durable or ephemeral.
The majority of education buildings in Poland are equipped with natural (gravity) ventilation, where the air inflow depends on the level of window airtightness. A complete statistical urban population of 50 school buildings in Czestochowa have been examined. The main issue to be clarified is the answer to the following questions: Is it theoretically possible to supply enough air to meet the ventilation requirements with gravity ventilation? What is the airtightness of the windows at which it will be possible? The average technical conditions of windows in the analysed buildings were bad. However, only in the case in which high external air leakage coefficient a = 7.0 m3/(h m daPa2/3) (q100KL = 32.4912 m3/(h m) is the amount of air passing through the leaks similar to the quantitative ventilation requirements for classrooms. The quantity of air flowing from the outside through modernized windows that meet the technical requirements (a = 0.6 to 1.0 m3/(m h daPa2/3)) covers on average only about 12% and about 21% of the ventilation needs. Without installing additional vents in the rooms, or better yet, installing mechanical ventilation with heat recovery, meeting the ventilation norm requirements will be impossible.
Good indoor air quality in school environment is crucial for teaching and learning processes, as well as student development. This study aims to identify the composition of PM2.5 and the main sources of it which influence the indoor and outdoor school environment. The PM2.5 sampling was conducted using a portable low volume air sampler and took place at three different primary schools. The chemical composition of PM2.5 is comprised of water-soluble inorganic ions (WSII) and potentially toxic trace metals. WSII (Cl⁻, NO3⁻, SO4²⁻, Na⁺, NH4⁺, K⁺, Mg²⁺, Ca²⁺) were analysed using ion chromatography (IC) and trace metals concentrations (Al, Fe, Zn, Cr, Cu, Mn, Pb, Ni, As, Co, Cd) using inductively coupled plasma-mass spectrometry (ICP-MS). The results showed that the highest average for PM2.5 concentrations in an indoor classroom was recorded at the school located in the industrial area (23.5 μg/m³) followed by urban (18.6 μg/m³) and suburban (9.58 μg/m³). The indoor to outdoor (I/O) ratio values for PM2.5 concentrations were slightly above one, indicating that open doors and windows highly affected indoor PM2.5 concentrations. Source apportionment analysis indicated that the sources of both indoor and outdoor PM2.5 were mixed of natural (crustal, mineral dust and sea salt) and anthropogenic (vehicle, industrial and biomass burning). The hazard quotient (HQ) value was lower than the acceptable limits. The excess lifetime cancer risk (ELCR) value for all three stations, however, was found to be slightly higher than the acceptable level (1.0E-06) for Cr and Ni.
The effectiveness of the two-dose COVID-19 vaccines has made reentry to in-person teaching, learning, and performing possible, despite singers’ special vulnerabilities to SARS-CoV-2 due to the virus’ airborne transmission route and the high-aerosol generating nature of singing. A number of factors may complicate a return to pre-pandemic conditions. This article provides resources to help teachers, singers, and collaborative pianists safely and ethically navigate a return to in-person singing by considering the following: effectiveness of vaccination and mask use; an update on aerosol risk; environmental risk factors and mitigation; the intersection of the privacy laws FERPA and HIPAA and vaccine hesitancy, and the psychological risks of reentry following the pandemic.
Cognitive functions refer to the set of brain-based skills to execute tasks of various difficulty levels. As people spend substantial time indoors, the indoor environmental quality (IEQ) influences occupants’ cognitive functions and consequently their learning and work performance. Previous studies have commonly examined the effects of IEQ on integrated learning or work performance, rather than specific cognitive skills. The present review decomposes IEQ into five factors—indoor air quality, the thermal environment, lighting, noise, and non-light visual factors. It divided cognition into five categories—attention, perception, memory, language function, and higher order cognitive skills—to better understand the relationship between IEQ and cognition. We conducted a detailed manual review of 66 focused studies and adopted co-occurrence analysis to generate landscapes of the associations between IEQ and cognition factors by analyzing keywords and abstracts of 8133 studies. Overall, results show that poor IEQ conditions are but not always associated with reduced cognition. However, the effects of a specific IEQ factor on different cognitive functions are quite distinct. Likewise, a specific cognitive function could be affected by different IEQ factors to varying degrees. Furthermore, the results suggest extensive inconsistencies in the relevant literature, especially regarding the effects of IAQ or thermal environment on cognition. Additionally, the keyword co-occurrence analysis identified more IEQ factors and cognitive functions emerging in the recent literature. Future studies are recommended to explore the factors causing the inconsistencies that we highlight here.
This chapter discusses the air pollutants that are found indoors, from what materials and sources they originate, their sampling and measurement, and how they affect human health by presenting case studies with an emphasis on residential buildings and schools. It also presents various indoor air quality (IAQ) guidelines, management, and technologies, as well as the impact of indoor environmental quality (IEQ) on health and comfort. Furthermore, the concept of green buildings is highlighted with its features related to building design and management, IAQ guides, organizations, and practices. The need for optimized buildings ventilation, air conditioning systems design, and indoor air purification to ensure IAQ is also presented. Active versus passive control methods of IAQ are reviewed and examples of residential and schools buildings are discussed in relation to sampling guidelines and IAQ practices. In addition, the IEQ, which in addition to IAQ extends to thermal conditions, noise, and light of an interior space, is expounded in view of the design of buildings, which need to function effectively in more aspects than those emphasized in current sustainability guidelines. Although significant progress has been made in the construction industry by following sustainability regulations, the emphasis has been on energy, water, and material savings. The current chapter makes the case that health, psychological, and productivity factors are equally important when considering the design, construction, and operation of buildings and, hence, need to be incorporated in current sustainability regulations.
Indoor Air Quality (IAQ) in classrooms has a significant impact on children’s academic performance, health and well‐being, therefore, understanding children’s perception of IAQ is vital. This study investigates how children’s perception of IAQ is affected by environmental variables and thermal sensation. In total, 29 naturally‐ventilated classrooms in eight UK primary schools were selected and 805 children were surveyed during Non‐Heating and Heating seasons. Results show that Air Sensation Votes (ASVs) are more correlated to CO2 levels than to operative temperatures (Top) during non‐heating seasons and more correlated to Top than CO2 levels during heating seasons. The impact of Top on ASVs decreases with an increase in CO2 levels and the effect of CO2 levels on ASVs decreases with increase in Top. The most favourable ASVs are given when children feel ‘cool’ and have ‘as it is’ preference. By keeping CO2<1000 ppm and Top within children’s thermal comfort band, ASVs are improved by 43%. The study recommends that standards should consider the impact of both temperature and CO2 levels on perceived IAQ. Perception of IAQ also affects children’s overall comfort and tiredness levels, however, this influence is more significant on tiredness level than that on overall comfort level.
Studies have proved that outdoor nitrogen dioxide (NO2) has adverse health effects for people. Nowadays, most people spend much more time indoors than outdoors, and the indoor NO2 concentration is affected by a variety of indoor and outdoor factors. In order to fully understand the relationship between indoor and outdoor NO2 concentrations, which is important for assessing human exposure to NO2, we reviewed and summarized the measured and modeled indoor/outdoor (I/O) NO2 concentration ratio based on a literature search of 218 publications in Web of Science and PubMed. The results showed that the I/O NO2 concentration ratio reported in the literature differed between countries and regions, thus indicating that differences existed in the indoor NO2 source strength and ventilation. The highest I/O NO2 concentration ratios were found for residential buildings, with cooking, smoking, and indoor combustion heating being the main indoor emission sources of NO2. Offices were associated with relatively few indoor sources, and schools had the least number of sources. For the same building type, seasonal differences in the indoor and outdoor NO2 concentrations were mainly due to the air change rate, which was highest during the summer. In this review, we also revisited physical-chemical principles-based models for NO2 and summarized the input parameters. The results of this study will facilitate more accurate estimations of human exposure to NO2, and consequently, better assessments of the health effects caused by NO2.
Building occupants are continuously exposed to multiple indoor environmental stimuli, including thermal, visual, acoustic, and air quality related factors. Moreover, personal and contextual aspects can be regarded as additional domains influencing occupants’ perception and behaviour. The scientific literature in this area typically deals with these multiple stimuli in isolation. In contrast to single-domain research, multi-domain research analyses at least two different domains, for example, visual and thermal. The relatively few literature reviews that have considered multi-domain approaches to indoor-environmental perception and behaviour covered only a few dozen articles each. The present contribution addresses this paucity by reviewing 219 scientific papers on interactions and cross-domain effects that influence occupants’ indoor environmental perception and behaviour. The objective of the present review is to highlight motivational backgrounds, key methodologies, and major findings of multi-domain investigations of human perception and behaviour in indoor environments. The in-depth review of these papers provides not only an overview of the state of the art, but also contributes to the identification of existing knowledge gaps in this area and the corresponding need for future research. In particular, many studies use “convenience” variables and samples, there is often a lack of theoretical foundation to studies, and there is little research linking perception to action.
In the following, measurements of CO 2 levels in seven classrooms in four schools are reported. Measurements were taken for approximately one week in each classroom during the heating season and the time-varying ventilation rates estimated. The results of the experiments show CO 2 concentrations which are far beyond the guideline value of 1000 ppm (the average concentration during the occupied period was 1957 ppm). In some classrooms the level exceeded the range of the detector (4000ppm). Calculated air supply rates vary from unacceptably low levels to rates which are in line with guidance (the average occupied rate was 0.84 ac/h or 1.38 l/s.p). The occurrence of periods with acceptable supply rates, and the rates found during purge ventilation, show that the surveyed classrooms have the potential to provide adequate fresh air. Anecdotal evidence from the classroom teachers suggest that the reason enough fresh air is not being provided is the reluctance of staff to open windows: firstly because of the draughts this might cause, and secondly, because they are unaware of a problem.
The aim of this study was to explore if there is any evidence for demonstrable impacts of school building design on the learning rates of pupils in primary schools.Hypotheses as to positive impacts on learning were developed for 10 design parameters within a neuroscience framework of three design principles. These were tested using data collected on 751 pupils from 34 varied classrooms in seven different schools in the UK. The multi-level model developed explained 51% of the variability in the learning improvements of the pupils, over the course of a year. However, within this a high level of explanation (73%) was identified at the “class” level, linked entirely to six built environment design parameters, namely: colour, choice, connection, complexity, flexibility and light.The model was used to predict the impact of the six design parameters on pupil’s learning progression. Comparing the “worst” and “best” classrooms in the sample, these factors alone were found to have an impact that equates to the typical progress of a pupil over one year. It was also possible to estimate the proportionate impact of these built environment factors on learning progression, in the context of all influences together. This scaled at a 25% contribution on average.This clear evidence of the significant impact of the built environment on pupils’ learning progression highlights the importance of this aspect for policy makers, designers and users. The wide range of factors involved in this holistic approach still leaves a significant design challenge.
This study analyzed the reporting of multilevel modeling applications of a sample of 99 articles from 13 peer-reviewed journals in education and the social sciences. A checklist, derived from the methodological literature on multilevel modeling and focusing on the issues of model development and specification, data considerations, estimation, and inference, was used to analyze the articles. The most common applications were two-level models where individuals were nested within contexts. Most studies were non-experimental and used nonprobability samples. The amount of data at each level varied widely across studies, as did the number of models examined. Analyses of reporting practices indicated some clear problems, with many articles not reporting enough information for a reader to critique the reported analyses. For example, in many articles, one could not determine how many models were estimated, what covariance structure was assumed, what type of centering if any was used, whether the data were consistent with assumptions, whether outliers were present, or how the models were estimated. Guidelines for researchers reporting multilevel analyses are provided.
Numerous epidemiological studies have demonstrated the association between particle mass (PM) concentration in outside air and the occurrence of health related problems and/or diseases. However, much less is known about indoor PM concentrations and associated health risks. In particular, data are needed on air quality in schools, since children are assumed to be more vulnerable to health hazards and spend a large part of their time in classrooms.On this background, we evaluated indoor air quality in 64 schools in the city of Munich and a neighbouring district outside the city boundary. In winter 2004–2005 in 92 classrooms, and in summer 2005 in 75 classrooms, data on indoor air climate parameters (temperature, relative humidity), carbon dioxide (CO2) and various dust particle fractions (PM10, PM2.5) were collected; for the latter both gravimetrical and continuous measurements by laser aerosol spectrometer (LAS) were implemented. In the summer period, the particle number concentration (PNC), was determined using a scanning mobility particle sizer (SMPS). Additionally, data on room and building characteristics were collected by use of a standardized form. Only data collected during teaching hours were considered in analysis. For continuously measured parameters the daily median was used to describe the exposure level in a classroom.The median indoor CO2 concentration in a classroom was 1603 ppm in winter and 405 ppm in summer. With LAS in winter, median PM concentrations of 19.8 μg m−3 (PM2.5) and 91.5 μg m−3 (PM10) were observed, in summer PM concentrations were significantly reduced (median PM2.5=12.7 μg m−3, median PM10=64.9 μg m−3). PM2.5 concentrations determined by the gravimetric method were in general higher (median in winter: 36.7 μg m−3, median in summer: 20.2 μg m−3) but correlated strongly with the LAS-measured results. In explorative analysis, we identified a significant increase of LAS-measured PM2.5 by 1.7 μg m−3 per increase in humidity by 10%, by 0.5 μg m−3 per increase in CO2 indoor concentration by 100 ppm, and a decrease by 2.8 μg m−3 in 5–7th grade classes and by 7.3 μg m−3 in class 8–11 compared to 1–4th class. During the winter period, the associations were stronger regarding class level, reverse regarding humidity (a decrease by 6.4 μg m−3 per increase in 10% humidity) and absent regarding CO2 indoor concentration. The median PNC measured in 36 classrooms ranged between 2622 and 12,145 particles cm−3 (median: 5660 particles cm−3).The results clearly show that exposure to particulate matter in school is high. The increased PM concentrations in winter and their correlation with high CO2 concentrations indicate that inadequate ventilation plays a major role in the establishment of poor indoor air quality. Additionally, the increased PM concentration in low level classes and in rooms with high number of pupils suggest that the physical activity of pupils, which is assumed to be more pronounced in younger children, contributes to a constant process of resuspension of sedimented particles. Further investigations are necessary to increase knowledge on predictors of PM concentration, to assess the toxic potential of indoor particles and to develop and test strategies how to ensure improved indoor air quality in schools.
This study presents the performance evaluation of a tailor-made passive sampler developed for the monitoring of tropospheric ozone.
The performance of the passive sampler was tested in the field conditions in terms of accuracy, precision, blank values, detection limit, effects of some parameters such as sampling site characteristics and sampling period on the field blanks, self-consistency, experimental and theoretical uptake rates, shelf life and comparison with commercial passive samplers.
There was an agreement (R (2) = 0.84) between the responses of passive sampler and the continuous automatic analyser. The accuracy of the sampler, expressed as percent relative error, was obtained lower than 15%. Method precision in terms of coefficient of variance for three simultaneously applied passive samplers was 12%. Sampler detection limit was 2.42 μg m(-3) for an exposure period of 1 week, and the sampler can be stored safely for a period of up to 8 weeks before exposure. Satisfactory self-consistency results showed that extended periods gave the same integrated response as a series of short-term samplers run side by side. The uptake rate of ozone was found to be 10.21 mL min(-1) in a very good agreement with the theoretical uptake rate (10.32 mL min(-1)). The results of the comparison study conducted against a commercially available diffusion tube (Gradko diffusion tube) showed a good linear relationship (R (2) = 0.93) between two passive samplers.
The sampler seems suitable to be used in large-scale measurements of ozone where no data are available or the number of existing automated monitors is not sufficient.
We measured volatile organic compound (VOC) exposures in multiple locations for a diverse population of children who attended two inner-city schools in Minneapolis, Minnesota. Fifteen common VOCs were measured at four locations: outdoors (O), indoors at school (S), indoors at home (H), and in personal samples (P). Concentrations of most VOCs followed the general pattern O approximately equal to S < P less than or equal to H across the measured microenvironments. The S and O environments had the smallest and H the largest influence on personal exposure to most compounds. A time-weighted model of P exposure using all measured microenvironments and time-activity data provided little additional explanatory power beyond that provided by using the H measurement alone. Although H and P concentrations of most VOCs measured in this study were similar to or lower than levels measured in recent personal monitoring studies of adults and children in the United States, p-dichlorobenzene was the notable exception to this pattern, with upper-bound exposures more than 100 times greater than those found in other studies of children. Median and upper-bound H and P exposures were well above health benchmarks for several compounds, so outdoor measurements likely underestimate long-term health risks from children's exposure to these compounds.
In contrast to the growth of fungi, the growth of mycobacteria in moisture-damaged building materials has rarely been studied.
Environmental mycobacteria were isolated from 23% of samples of moisture-damaged materials (n = 88). The occurrence of mycobacteria increased with increasing concentrations of fungi. Mycobacteria may contribute to indoor
exposure and associated adverse health effects.
Measurements of metabolic carbon dioxide concentration made in four classrooms in two schools are reported for both occupied and unoccupied periods. Measurements were taken for approximately one week in each classroom during the unheated season and the time-varying ventilation rates estimated. The results of the experiments show CO2 concentrations that are far beyond the guideline value of 1000 ppm (the maximum concentration during the occupied period was 3756 ppm). Calculated air supply rates vary from unacceptably low levels, to rates that are in line with guidance. The occurrence of periods with acceptable supply rates, and the rates found during purge ventilation, show that the surveyed classrooms have the potential to provide adequate fresh air. Inaccessible windows and ventilation openings, combined with lack of guidance on when and how to apply ventilation seems to be the primary reason for poor ventilation outside the heating season.
SAS PROC MIXED is a flexible program suitable for fitting multilevel models, hierarchical linear models, and individual growth models. Its position as an integrated program within the SAS statistical package makes it an ideal choice for empirical researchers and applied statisticians seeking to do data reduction, management, and analysis within a single statistical package. Because the program was developed from the perspective of a "mixed" statistical model with both random and fixed effects, its syntax and programming logic may appear unfamiliar to users in education and the social and behavioral sciences who tend to express these models as multilevel or hierarchical models. The purpose of this paper is to help users familiar with fitting multilevel models using other statistical packages (e.g., HLM, MLwiN, MIXREG) add SAS PROC MIXED to their array of analytic options. The paper is written as a step-by-step tutorial that shows how to fit the two most common multilevel models: (a) school effects models, designed for data on individuals nested within naturally occurring hierarchies (e.g., students within classes); and (b) individual growth models, designed for exploring longitudinal data (on individuals) over time. The conclusion discusses how these ideas can be extended straighforwardly to the case of three level models. An appendix presents general strategies for working with multilevel data in SAS and for creating data sets at several levels.
This study aims to assess the adequacy of current guidelines, framed around thermal comfort, estimated ventilation rates, and CO2 levels, for the provision of indoor air quality (IAQ) in school classrooms. It draws on detailed monitoring data from a sample of 18 classrooms from 6 London schools. Overheating during the non-heating season was identified in eight south-, south-east-, and east-facing classrooms in two Victorian and two contemporary schools. Four classrooms in these contemporary schools also failed to keep average indoor CO2 levels below 1500 ppm in the non-heating season. During the heating season, eight classrooms exceeded the daily average indoor CO2 levels. Mean indoor particulate matter (PM)10 and PM2.5 levels recorded in all classrooms in both seasons were higher than 20 and 10 μg/m3, respectively, indicating that school exposure during an academic year may exceed annual recommended WHO [2006. Air Quality Guidelines: Global Update 2005: Particulate Matter, Ozone, Nitrogen Dioxide, and Sulfur Dioxide. Copenhagen: WHO Regional Office for Europe; 2010. WHO Guidelines for Indoor Air Quality: Selected Pollutants. Copenhagen: WHO Regional Office for Europe.] guideline values in all classrooms. In both seasons, all classrooms were found to have indoor total volatile organic compounds levels (median: 269 ppb and interquartile range: 64–408 ppb) above guideline thresholds (130 ppb) associated with sensory irritations. Identification of specific volatile organic compounds indicated the presence of strong indoor sources including furniture, cleaning products, and teaching materials. Findings suggest that these school classrooms often have poor IAQ due to a combination of sub-optimal building operation and management practices. Furthermore, while CO2 and ventilation rates are a useful tool for IAQ assessment, findings indicate that consideration of specific pollutants is necessary to ensure a healthy indoor environment.
The overall aim of the study is to provide empirical evidence on indoor pollution levels to assist the formation of indoor air quality (IAQ) benchmarking of school buildings under operational conditions. This article is the second part of the study and aims to quantify seasonal variation of chemical and microbial levels in London schools. Passive diffusive sampling was employed for radon, NO2, and O3 measurements. Fungal and bacterial groups and allergens were sampled with suction-based methods in settled dust and endotoxin levels were sampled in dust collected with natural deposition. Biological contaminants were analysed with molecular, cultivation-independent methods. The strong temporal and spatial variability of outdoor NO2 levels affected indoor levels and is therefore an important consideration when selecting sites for new school buildings. There is a need to further clarify on the effect of finishing, such as wall-to-wall carpeting, which may act as a significant reservoir of irritants and allergens and impact school IAQ.
Researchers in comparative research increasingly use multilevel models to test effects of country-level factors on individual behavior and preferences. However, the asymptotic justification of widely employed estimation strategies presumes large samples and applications in comparative politics routinely involve only a small number of countries. Thus, researchers and reviewers often wonder if these models are applicable at all. In other words, how many countries do we need for multilevel modeling? I present results from a large-scale Monte Carlo experiment comparing the performance of multilevel models when few countries are available. I find that maximum likelihood estimates and confidence intervals can be severely biased, especially in models including cross-level interactions. In contrast, the Bayesian approach proves to be far more robust and yields considerably more conservative tests.
The increasing interest in indoor environmental quality of educational buildings has been underpinned by the rising incidence of asthma and respiratory disease among children, who spend a substantial amount of their lives on the school premises. The susceptibility of children to respiratory disease compared with adults has led to the formulation of regulatory frameworks for the school environment, which specifies maximum CO2 concentrations and minimum airflow rates. This article reviews the evidence that school buildings provide a healthy and satisfactory indoor environment for the occupants. It summarized air pollution levels reported from indoor air quality (IAQ) monitoring surveys and evidence linking school exposure with health responses from the occupants. In addition, environmental and behavioural factors affecting pollution levels in school buildings were examined. The analysis has highlighted the degraded IAQ in some schools that often exceed WHO guidelines, while health impacts of school exposure were reported for concentrations below current guidelines.
Modern building materials, once moistened, may provide ecological niches for various microbes that have not been well characterized. The aim of the current study was to determine whether fungal genera and actinobacteria were associated with seven types of moisture-damaged building materials by systematically describing the mycobiota and enumerating fungi and bacteria in these materials. Microbial analyses were obtained from 1140 visibly damaged samples of building material, viz. wood, paper, non-wooden building boards, ceramic products, mineral insulation materials, paints and glues, and plastics. Fungal and bacterial concentrations correlated well (r=0.6). The range of fungi and bacteria numbers was between 100 and in all materials, but significant differences in counts were observed between materials. Highest median concentrations of fungi were observed in wooden and paper materials, and lowest in samples of mineral insulation, ceramic products, and paints and glues. Concentrations of viable bacteria in mineral insulation materials were significantly lower than in wood, paper, ceramic products and plastics. A rich variety of fungi was found in wooden materials, with Penicillium and yeasts occurring most frequently. In paper materials, a clear difference from wood was the more frequent occurrence of Cladosporium and Stachybotrys. The most distinctive finding in gypsum boards was that Stachybotrys was common. Ceramic products and paints and glues seemed to favour Acremonium and Aspergillus versicolor. Yeasts and members of the Sphaeropsidales occurred often in parallel in most materials. This study confirms that microbial growth occurs in many different building materials and shows associations between fungal genera and the type of material.
SAS PROC MIXED is a flexible program suitable for fitting multilevel models, hierarchical linear models, and individual growth models. Its position as an integrated program within the SAS statistical package makes it an ideal choice for empirical researchers and applied statisticians seeking to do data reduction, management, and analysis within a single statistical package. Because the program was developed from the perspective of a "mixed" statistical model with both random and fixed effects, its syntax and programming logic may appear unfamiliar to users in education and the social and behavioral sciences who tend to express these models as multilevel or hierarchical models. The purpose of this paper is to help users familiar with fitting multilevel models using other statistical packages (e.g., HLM, MLwiN, MIXREG) add SAS PROC MIXED to their array of analytic options. The paper is written as a step-by-step tutorial that shows how to fit the two most common multilevel models: (a) school effects models, designed for data on individuals nested within naturally occurring hierarchies (e.g., students within classes); and (b) individual growth models, designed for exploring longitudinal data (on individuals) over time. The conclusion discusses how these ideas can be extended straighforwardly to the case of three level models. An appendix presents general strategies for working with multilevel data in SAS and for creating data sets at several levels.
This book covers a broad range of topics about multilevel modeling. The goal is to help readersto understand the basic concepts, theoretical frameworks, and application methods of multilevel modeling. Itis at a level also accessible to non-mathematicians, focusing on the methods and applications of various multilevel models and using the widely used statistical software SAS.Examples are drawn from analysis of real-world research data. © 2012 Higher Education Press and Walter de Gruyter GmbH & Co. KG, Berlin/Boston.
The measurement of indoor air pollutants and their health effects are less often studied due to the costs
of collection of such data. We have analysed the variability in the measurement of five indoor school air
pollutants: fine particulate matter of size <2.5 µm (PM2.5), nitrogen dioxide (NO2), and three Volatile
Organic Compounds (VOC), namely formaldehyde, acetaldehyde and acrolein, objectively measured over
five days of a week at representative points in more than 400 classrooms of 109 schools and courtyards in
six French cities spread out over the year. Separate 3-stage multilevel models were fitted to partition the
different nested variance components (i.e., classroom, school and city levels), and intra-class correlation
(ICC) coefficients were computed to bring out the similarities of pollutants’ concentrations among these
spatial units. The indoor PM2.5 and NO2 concentrations showed a high degree of similarity (ICC coefficients
equal to 76% and 81%, respectively) between the classrooms of a school (and city), whereas the
formaldehyde, acetaldehyde and acrolein concentrations showed low to moderate degree of similarity
(ICC coefficients equal to 25%, 36% and 57%, respectively) between the classrooms. We conclude that to
investigate the impact of indoor air pollutants, a multilevel approach taking into account the full design
of the study would be the most appropriate.
Previous studies have found that classrooms are often inadequately ventilated, with the resultant increased risk of negative impacts on the pupils. This paper describes a series of field measurements that investigated the indoor air quality, thermal comfort and acoustic performance of nine recently built secondary schools in England. The most significant conclusion is that the complex interaction between ventilation, thermal comfort and acoustics presents considerable challenges for designers. The study showed that while the acoustic standards are demanding it was possible to achieve natural ventilation designs that met the criteria for indoor ambient noise levels when external noise levels were not excessive. Most classrooms in the sample met the requirement of limiting the daily average CO2 concentration to below 1500 ppm but just a few met the need to readily provide 8 l/s per person of fresh air under the easy control of the occupants. It would seem that the basic requirement of 1500 ppm of CO2 is achieved as a consequence of the window areas being just sufficient to provide the minimum of 3 l/s per person at low and intermittent occupancy. Thermal comfort in the monitored classrooms was mostly acceptable but temperatures tended to be much higher in practice than the design assumed.
Under the French national research program PRIMEQUAL, measurements of outdoor and indoor pollution have been performed in eight school buildings in La Rochelle (France) and its suburbs. The school buildings were either naturally ventilated by opening the windows or mechanically ventilated with minimum fresh air, and demonstrated various permeabilities. Ozone, nitrogen oxides (NO and NO2), and particulate matter (PM) (15 size intervals ranging from 0.3 to 20 μm) concentrations were monitored continuously indoors and outdoors for two 2-week periods. The indoor relative humidity, temperature, CO2 concentration (room occupancy), window openings and permeability of the building were also measured. Principal component analysis (PCA), a multivariate observation-based statistical method, was used to determine the parameters influencing the relationship between the outdoor and indoor concentration levels. After a brief description of the experimental data and methodology, the paper presents a detailed analysis of the PCA diagrams. This analysis leads to distinguish between positively correlated, negatively correlated and non-correlated variables. The main conclusions arising from the study are: (1) the influence of the room occupancy on the particle concentrations indoors changes with different particle sizes, (2) the building air-tightness and the outdoor concentration level greatly influence the indoor/outdoor (I/O) concentration ratios of ozone, and (3) indoor ozone and particles concentrations are negatively correlated, which may be the result of complex homogeneous and/or heterogeneous processes.
Several studies have investigated the health of children attending schools located near busy roads. In this study, we have measured personal exposure to traffic-related pollutants in children to validate exposure classification based on school location. Personal exposure to PM2.5, soot, NOx and NO2 was measured during four 48-h periods. The study involved 54 children attending four different schools, two of which were located within 100 m of a major road (one ring road and one freeway) and the other two were located at a background location in the city of Utrecht, The Netherlands. Outdoor monitoring was conducted at all school sites, during the personal measurements. A questionnaire was administered on time activity patterns and indoor sources at home. The outdoor concentration of soot was 74% higher at the freeway school compared to its matched background school. Personal exposure to soot was 30% higher. For NOx the outdoor concentration was 52% higher at the freeway school compared to its background school. The personal concentration of NOx was 37% higher for children attending the freeway school. Differences were smaller and insignificant for PM2.5 and NO2. No elevated personal exposure to air pollutants was found for the children attending the school near the ring road. We conclude that the school's proximity to a freeway can be used as a valid estimate of exposure in epidemiological studies on the effects of the traffic-related air pollutants soot and NOx in children.
A study on indoor–outdoor RSPM (PM10, PM2.5 and PM1.0) mass concentration monitoring has been carried out at a classroom of a naturally ventilated school building located near an urban roadway in Delhi City. The monitoring has been planned for a year starting from August 2006 till August 2007, including weekdays (Monday, Wednesday and Friday) and weekends (Saturday and Sunday) from 8:0 a.m. to 2:0 p.m., in order to take into account hourly, daily, weekly, monthly and seasonal variations in pollutant concentrations. Meteorological parameters, including temperature, rH, pressure, wind speed and direction, and traffic parameters, including its type and volume has been monitored simultaneously to relate the concentrations of indoor–outdoor RSPM with them. Ventilation rate has also been estimated to find out its relation with indoor particulate concentrations. The results of the study indicates that RSPM concentrations in classroom exceeds the permissible limits during all monitoring hours of weekdays and weekends in all seasons that may cause potential health hazards to occupants, when exposed. I/O for all sizes of particulates are greater than 1, which implies that building envelop does not provide protection from outdoor pollutants. Further, a significant influence of meteorological parameters, ventilation rate and of traffic has been observed on I/O. Higher I/O for PM10 is indicating the presence of its indoor sources in classroom and their indoor concentrations are strongly influenced by activities of occupants during weekdays.
Abstract
Abstract Indoor air quality (IAQ) parameters in 64 elementary and middle school classrooms in Michigan were examined for the purposes of assessing ventilation rates, levels of volatile organic compounds (VOCs) and bioaerosols, air quality differences within and between schools, and emission sources. In each classroom, bioaerosols, VOCs, CO2, relative humidity, and temperature were monitored over one workweek, and a comprehensive walkthough survey was completed. Ventilation rates were derived from CO2 and occupancy data. Ventilation was poor in many of the tested classrooms, e.g., CO2 concentrations often exceeded 1000 ppm and sometimes 3000 ppm. Most VOCs had low concentrations (mean of individual species <4.5 μg/m3); bioaerosol concentrations were moderate (<6500 count per m3 indoors, <41,000 count per m3 outdoors). The variability of CO2, VOC, and bioaerosol concentrations within schools exceeded the variability between schools. These findings suggest that none of the sampled rooms were contaminated and that no building-wide contamination sources were present. However, localized IAQ problems might remain in spaces where contaminant sources are concentrated and that are poorly ventilated.
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There are few incidence studies on sick building syndrome (SBS). We studied two-year change of SBS in Chinese pupils in relation to parental asthma/allergy (heredity), own atopy, classroom temperature, relative humidity (RH), absolute humidity (AH), crowdedness, CO₂, NO₂, and SO₂. A total of 1993 participated at baseline, and 1143 stayed in the same classrooms after two years. The prevalence of mucosal and general symptoms was 33% and 28% at baseline and increased during follow-up (P < 0.001). Twenty-seven percent reported at least one symptom improved when away from school. Heredity and own atopy were predictors of SBS at baseline and incidence of SBS. At baseline, SO₂ was associated with general symptoms (OR=1.10 per 100 μg/m³), mucosal symptoms (OR=1.12 per 100 μg/m³), and skin symptoms (OR=1.16 per 100 μg/m³). NO₂ was associated with mucosal symptoms (OR=1.13 per 10 μg/m³), and symptoms improved when away from school (OR=1.13 per 10 μg/m³). Temperature, RH, AH, and CO₂ were negatively associated with prevalence of SBS. Incidence or remission of SBS was not related to any exposure, except a negative association between SO₂ and new skin symptoms. In conclusion, heredity and atopy are related to incidence and prevalence of SBS, but the role of the measured exposures for SBS is more unclear.
Practical implications:
We found high levels of CO₂ indicating inadequate ventilation and high levels of SO₂ and NO₂, both indoors and outdoors. All schools had natural ventilation, only. Relying on window opening as a tool for ventilation in China is difficult because increased ventilation will decrease the level of CO₂ but increase the level of NO₂ and SO₂ indoors. Prevalence studies of sick building syndrome (SBS) might not be conclusive for causal relationships, and more longitudinal studies on SBS are needed both in China and other parts of the world. The concept of mechanical ventilation and air filtration should be introduced in the schools, and when planning new schools, locations close to heavily trafficked roads should be avoided.
Microbiological analysis of atmospheres witnessed substantial technical improvements in the 1940s to 1960s. May's cascade impactor and Hirst's spore trap allowed the counting of total cells but had limited capacity for identification of the spores. Bourdillon's sampler enabled the counting of cultivable fungi and their identification. A great step forward was given with the Andersen's six-stage impactor, which allowed discrimination of particles by size, counting of cultivable cells, and species identification. This period also witnessed the development of impingers, namely, the AGI-30 described by Malligo and Idoine, and the three-stage model designed by K. R. May. The 1990s to 2000s witnessed innovative discoveries on the biology of indoor fungi. Work carried out in several laboratories showed that indoor fungi can release groups of spores, individual spores and fungal fragments, and produce volatile organic compounds and mycotoxins. Integrating all findings a holistic interpretation emerged for the sick building syndrome. Healthy houses and buildings, with low indoor humidity, display no appreciable indoor fungal growth, and outdoor Cladosporium dominates. On the contrary, in sick houses and buildings, high indoor humidity allows fungal growth (mainly of Penicillium and Aspergillus), with concomitant release of conidia and fragments into the atmosphere. The intoxication probably results from a chronic exposure to volatile organic compounds and mycotoxins produced by Penicillium, Aspergillus, and Stachybotrys.
Relatively little is known about exposures to traffic-related particulate matter at schools located in dense urban areas. The purpose of this study was to examine the influences of diesel traffic proximity and intensity on ambient concentrations of fine particulate matter (PM(2.5)) and black carbon (BC), an indicator of diesel exhaust particles, at New York City (NYC) high schools. Outdoor PM(2.5) and BC were monitored continuously for 4-6 weeks at each of 3 NYC schools and 1 suburban school located 20 kilometers upwind of the city. Traffic count data were obtained using an automated traffic counter or video camera. BC concentrations were 2-3 fold higher at urban schools compared with the suburban school, and among the 3 urban schools, BC concentrations were higher at schools located adjacent to highways. PM(2.5) concentrations were significantly higher at urban schools than at the suburban school, but concentrations did not vary significantly among urban schools. Both hourly average counts of trucks and buses and meteorological factors such as wind direction, wind speed, and humidity were significantly associated with hourly average ambient BC and PM(2.5) concentrations in multivariate regression models. An increase of 443 trucks/buses per hour was associated with a 0.62 mug/m(3) increase in hourly average BC at a NYC school located adjacent to a major interstate highway. Car traffic counts were not associated with BC. The results suggest that local diesel vehicle traffic may be important sources of airborne fine particles in dense urban areas and consequently may contribute to local variations in PM(2.5) concentrations. In urban areas with higher levels of diesel traffic, local, neighborhood-scale monitoring of pollutants such as BC, which compared to PM(2.5), is a more specific indicator of diesel exhaust particles, may more accurately represent population exposures.
Collecting data from students within classrooms or schools, and collecting data from students on multiple occasions over time, are two common sampling methods used in educational research that often require multilevel modeling (MLM) data analysis techniques to avoid Type-1 errors. The purpose of this article is to clarify the seven major steps involved in a multilevel analysis: (1) clarifying the research question, (2) choosing the appropriate parameter estimator, (3) assessing the need for MLM, (4) building the level-1 model, (5) building the level-2 model, (6) multilevel effect size reporting, and (7) likelihood ratio model testing. The seven steps are illustrated with both a cross-sectional and a longitudinal MLM example from the National Educational Longitudinal Study (NELS) dataset. The goal of this article is to assist applied researchers in conducting and interpreting multilevel analyses and to offer recommendations to guide the reporting of MLM analysis results.
A middle school (grades 6 to 8) in a residential section of Springfield, Illinois, with no known air quality problems, was selected for a baseline indoor air quality survey. The study was designed to measure and evaluate air quality at the middle school with the objective of providing a benchmark for comparisons with measurements in schools with potential air quality problems. The focus of this article is on the development of emission factors for particulate matter and bioaerosols. The school was characterized as having no health complaints and good maintenance schedules. Four indoor locations including the cafeteria, a science classroom, an art classroom, the lobby outside the main office, and one outdoor location were sampled for various environmental comfort and pollutant parameters for one week in February 1997. Integrated samples (eight-hour sampling time) for respirable and total particulate matter, and short-term measurements (two-minute samples, three times per day) for bioaerosols were collected on three consecutive days at each of the sampling sites. Continuous measurements of carbon dioxide were logged at all locations for five days. Continuous measurements of respirable particulate matter were also collected in the lobby area. A linear relationship between occupancy and corresponding carbon dioxide and particle concentrations was seen. A completely mixed space, one compartment mass balance model with estimated CO2 generation rates and actual CO2 and particulate matter concentrations was used to model ventilation and pollutant emission rates. Emission factors for occupancy were represented by the slope of emission rate versus occupancy scatter plots. The following particle and bioaerosol emission factors were derived from the indoor measurements: total particles: 1.28 mg/hr/person-hr; respirable particles: 0.154 g/hr/person-hr; total fungi: 167 CFU/hr/person-min; thermophilic fungi: 35.8 CFU/hr/person-min; mesophilic fungi: 119 CFU/hr/person-min; total bacteria: 227 CFU/hr/person-min; gram-negative bacteria: 69.5 CFU/hr/person-min; gram-positive bacteria: 191 CFU/hr/person-min; Aspergillus: 17.0 CFU/hr/person-min; Penicillium: 161 CFU/hr/person-min; and yeasts: 16.4 CFU/hr/person-min.
In order to study the influence of furnishings and cleaning on the indoor air quality at school, 181 randomly chosen classrooms were investigated. The amounts of open shelves, textiles and other fittings were noted, data were gathered on cleaning routines, and a number of pollutants were measured in the classrooms. In classrooms with more fabrics there was more settled dust and the concentration of formaldehyde was higher. Classrooms with more open shelves had more formaldehyde, and more pet allergens in settled dust, and classrooms with a white board, instead of a chalk board, were less dusty. Classrooms mainly cleaned through wet mopping had more airborne viable bacteria but less settled dust than classrooms mainly cleaned by dry methods. In rooms where the desks and curtains were more often cleaned, the concentrations of cat and dog allergen in settled dust were lower. It is concluded that furnishings and textiles in the classroom act as significant reservoirs of irritants and allergens and have an impact on the indoor air quality at school.
Choosing the appropriate floor surface for a school environment is a complex issue. To assist school personnel in determining which flooring is best for their school, we studied the biocontaminant levels associated with carpeted and hard surface flooring. Two schools were selected, one predominantly tiled and one predominantly carpeted, as similar as possible with the exception of their floor coverings. Neither school was a "problem" building. Multiple biocontaminants were measured. For flooring, there were statistically significant differences for all the tested biocontaminants except fungi. The carpeted surfaces, being strong sinks, generally had higher surface loadings of the biocontaminants, while the airborne levels were significantly higher over tiled floors. Significant differences in airborne levels were found for dust mass, spores, fungi, beta-1,3 glucans, and endotoxins. The results suggest that carpet flooring was not the major contributor to airborne levels of biocontaminants in these two nonproblem schools.
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In the frame of the French national research program PRIMEQUAL (inter-ministry program for better air quality in urban environments), measurements of outdoor and indoor pollution have been carried out in eight schools in La Rochelle (France) and its suburbs. The buildings were naturally ventilated by opening the windows, or mechanically ventilated, and showed various air permeabilities. Ozone, nitrogen oxides (NO and NO(2)), and airborne particle (particle counts within 15 size intervals ranging from 0.3 to 15 mum) concentrations were continuously monitored indoors and outdoors for two 2-week periods. The indoor humidity, temperature, CO(2) concentration (an indicator of occupancy), window openings and building permeability were also measured. The temporal profiles of indoor and outdoor concentrations show ozone and nitrogen oxides behave differently: NO and NO(2) indoor/outdoor concentration ratios (I/O) were found to vary in a range from 0.5 to 1, and from 0.88 to 1, respectively, but no correlation with building permeability was observed. On the contrary, I/O ratios of ozone vary in a range from 0 to 0.45 and seem to be strongly influenced by the building air-tightness: the more airtight the building envelope, the lower the ratio. Occupancy, through re-suspension of previously deposited particles and possible particle generation, strongly influences the indoor concentration level of airborne particles. However, this influence decreases with particle size, reflecting the way deposition velocities vary as a function of size. The influence of particle size on deposition and penetration across the building envelope is also discussed by analyzing the I/O ratios measured when the buildings were unoccupied, by comparing the indoor concentrations measured when the buildings were occupied and when they were not (O/U ratios), and by referring to previously published studies focussing on this topic. Except one case, I/O were found to vary in the range from 0.03 to 1.79. All O/U are greater than one and increase up to 100 with particle size.
Practical implications:
Assessing children's total exposure requires the knowledge of outdoor and indoor air contaminant concentrations. The study presented here provides data on compared outdoor and indoor concentration levels in school buildings, as well as information on the parameters influencing the relationship between outdoor and indoor air quality. It may be used as a basis for estimating indoor concentrations from outdoor concentrations data, or as a first step in designing buildings sheltering children against atmospheric pollution.