Article

The effect of an ion generator on indoor air quality in a residential room

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Abstract

Abstract Ion generators charge particles with a corona prior to their removal on collector plates or indoor surfaces and also emit ozone, which can react with terpenes to yield secondary organic aerosol, carbonyls, carboxylic acids, and free radicals. This study characterized the indoor air quality implications of operating an ion generator in a 27 m3 residential room, with four different test room configurations. Two room configurations had carpet overlaying the original flooring of stained/sealed concrete, and for one configuration with and without carpet, a plug-in air freshener was used as a terpene source. Measurements included airborne sampling of particulate matter (0.015–20 μm), terpenes and C1–C4 and C6–C10 aldehydes, ozone concentrations, and air exchange rates. When the heating, ventilating, and air-conditioning system was not operating (room air exchange rate = ∼0.5/h), the use of the ion generator in the presence of the air freshener led to a net increase in ultrafine particles (<0.1 μm). Also, increased concentrations of ozone were observed regardless of air freshener presence, as well as increases in formaldehyde and nonanal, albeit within measurement uncertainty in some cases. Thus, it may be prudent to limit ion generator use indoors until evidence of safety can be ascertained. Portable ion generators are intended to clean the air of particles, but they may emit ozone as a byproduct of their operation, which has the potential to degrade indoor air quality. This study showed that under certain conditions in a residential room, the use of a portable ion generator can increase concentrations of ozone and, to a lesser degree, potentially aldehydes. Also, if operated in the presence of a plug-in air freshener that emits terpenes, its use can increase concentrations of secondary organic aerosol in the ultrafine size range.

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... When a filter becomes a source of secondary pollution releasing particles or introducing by-products, the indoor air quality is degraded. Indeed, mechanical filters can be a source of contamination from micro-organism, as electrostatic filters may increase the concentration of ultrafine particles, ozone and formaldehyde [17], [18]. Adsorbent air filters are not generating by-products but there is a possibility of pollutant reemission when saturation occurs. ...
... [2], [3], [18], [20] Adsorbent filter -+ Most efficient commercial technology in VOCs removal. Saturation, cause of re-emission. ...
Conference Paper
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A variety of air filtration technologies are commercially available for reducing particles and gaseous contaminants that may enter buildings from outside. According to the World Health Organization (WHO), there is an increasing range of adverse health effects linked to air pollution, at even-lower concentration of pollutants. This article presents a short literature overview of air filtration technologies, which focus on assessing their ability in removing both particles and gaseous compounds. The aim is to provide information about current research development of air filtration technologies as well as their advantages, limitations and performance in terms of removal efficiency, pressure drop and formation of by-products. Mechanical filters and electrostatic filters are efficiently used for the removal of particles. Photocatalytic oxidant and adsorbent air filters are commonly used for gas removal. These last two types of filters are not feasible for particles removal. Air filtration using electrospun nanofiber filters have been studied, however, the performance of such filters for the removal of particles and gaseous contaminants at the same time has to be further investigated.
... Dong et al. (2019) studied the effects of ionization-based air purifiers on the concentration of PM, BC, in classrooms and found that the concentration reduction for PM 2.5 , PM 10 , BC was 44 %, 34 % and 50 %, respectively. Waring and Siegel (2011) in their study found that use of ionization air purifier can though reduce the particle concentration slightly, but it is associated with increased concentrations of UFPs, ozone, and VOCs that are harmful to human health. Therefore, ASHRAE recommends that the air purifiers that generates ozone as secondary pollutant should not be used in occupied spaces because of negative health effects that arise from exposure to ozone and its reaction products (Wargocki et al., 2015). ...
Article
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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.
... Air ions have a primary role in the discipline of atmospheric electricity, because their motion in the atmosphere is integral to the air conductivity (Wilson, 1924;Israël, 1970;Tinsley, 2008). Air ions have also raised the interest of aerosol scientists because of their participation in atmospheric aerosol formation and thus they have influence on air quality, human health, and climate (Gunn, 1954;Bricard et al., 1968;Hõrrak et al., 1998;Yu and Turco, 2008;Manninen et al., 2010;Waring and Siegel, 2011). ...
Article
Full-text available
An air ion spectrometer (AIS) was deployed for the first time at the Concordia station at Dome C (75°06′ S, 123°23′ E; 3220 m a. s. l. ), Antarctica during the period 22 December 2010–16 November 2011 for measuring the number size distribution of air ions. In this work, we present results obtained from this air ion data set together with aerosol particle and meteorological data. The main processes that modify the number size distribution of air ions during the measurement period at this high-altitude site included new particle formation (NPF, observed on 85 days), wind-induced ion formation (observed on 36 days), and ion production and loss associated with cloud/fog formation (observed on 2 days). For the subset of days when none of these processes seemed to operate, the concentrations of cluster ions (0.9–1.9 nm) exhibited a clear seasonality, with high concentrations in the warm months and low concentrations in the cold. Compared to event-free days, days with NPF were observed with higher cluster ion concentrations. A number of NPF events were observed with restricted growth below 10 nm, which were termed as suppressed NPF. There was another distinct feature, namely a simultaneous presence of two or three separate NPF and subsequent growth events, which were named as multi-mode NPF events. Growth rates (GRs) were determined using two methods: the appearance time method and the mode fitting method. The former method seemed to have advantages in characterizing NPF events with a fast GR, whereas the latter method is more suitable when the GR was slow. The formation rate of 2 nm positive ions (J2+) was calculated for all the NPF events for which a GR in the 2–3 nm size range could be determined. On average, J2+ was about 0.014 cm−3 s−1. The ion production in relation to cloud/fog formation in the size range of 8–42 nm seemed to be a unique feature at Dome C, which has not been reported elsewhere. These ions may, however, either be multiply charged particles but detected as singly charged in the AIS, or be produced inside the instrument, due to the breakage of cloud condensation nuclei (CCN), possibly related to the instrumental behaviour under the extremely cold condition. For the wind-induced ion formation, our observations suggest that the ions originated more likely from atmospheric nucleation of vapours released from the snow than from mechanical charging of shattered snow flakes and ice crystals.
... ventilation channels. If ozone sources like, e.g., special air purifiers (Waring and Siegel, 2010), are present indoors, the room ozone concentration can exceed outdoor concentrations considerably which can accelerate the particle-generating chemistry (Hubbard et al., 2005). Ozone is also considerably degraded on the surfaces of wooden building products which can be characterized by their deposition velocity. ...
Article
Wooden building products indoors are known to be able to affect the perceived air quality depending on their emission strength. The indoor application of modern ecological lacquer systems (eco-lacquers or ‘green’ lacquers) may be a much stronger source than the substrates itself. Especially with regard to the formation of ultrafine particles by gas-to-particle conversion in the presence of ozone or other reactive species the impact of the applied building products on the indoor air quality has to be addressed. The present study reports a two concentration step ozonation of OSB panels, painted beech boards, and a number of solid ‘exotic’ wood types in a 1 m³ emission test chamber. The emission of volatile organic compounds (VOC) was recorded as well as the formation of ultrafine particles in the range 7–300 nm. The products are characterized on the basis of their ozone deposition velocity; the obtained values of 0.008–0.381 cm s−1 are comparable with previously published data. Within the samples of the present study one eco-lacquer was the strongest source of VOC (total VOC ∼ 60 mg m−3) while the wooden building products (OSB) were of intermediate emission strength. The lowest emission was found for the solid (exotic) wood samples. The VOC release of the samples corresponded roughly to the particle formation potential. However, the strongest UFP formation was measured for one solid wood sample (‘Garapa’) which showed a strong surface reaction in the presence of ozone and formed a large number of particles <40 nm. Overall, the experiments demonstrated the necessity of real-life samples for the estimation of UFP indoor air pollution from the ozone chemistry of terpenes.
... Aerosol particles are defined as suspended solid or liquid particles in a gas and they are regarded as significant pollutant sources in the indoor environment. As mentioned, since the residential house is the main indoor environment in which people, especially children spend their time, the majority of researches focus on the indoor aerosol particles in residential spaces [2][3][4][5]. Indoor particle sources play an important role in the indoor air quality and occupant exposure to the indoor particles from indoor sources is quantified as an important step toward assessing their role in health risk. Numerous investigations have been done to identify the indoor particle sources such as: smoking, kerosene heaters, humidifiers, wood stoves, electric motors, cooking, and re-suspension of particles [6][7][8][9][10][11][12][13][14][15][16]. ...
Article
Many studies have been shown the advantage of low-energy heating systems, such as floor heating system in comparison with high-energy consuming systems, such as radiator heating system. The adoption of these energy-efficient heating systems still requires the provision of acceptable indoor air quality. In this research, three-dimensional comparison of deposition and dispersion of airborne particles in two radiator and floor heating systems is investigated numerically by an Eulerian–Lagrangian method. In an attempt to provide such data, the deposition of solid particles ranging from 0.3 to 10 μm is calculated and the main goal is to survey the removal efficiency of these two heating systems. The model validation is performed through result comparisons with published data from literatures. The results indicate that deposition ratio of particles is higher in radiator heating system. Furthermore, the numerical results show that the floor and radiator heating systems trend to deposit the suspended particles on the ceiling and on the floor, respectively.
... Aside from airflow rate measurements at the air handler, it may be critical to measure the operational cycles of the HVAC system and the actual amount of airflow entering or leaving a space. Runtime fractions can be assessed using a combination of supply temperature measurements [99,100], measurements of the electrical power draw of AHU fans and/or compressor units [101,102], or by vibration or magnetic sensors on AHU blowers or compressor motors [103]. Supply temperature measurements can also reveal whether an HVAC system is operating in heating or cooling modes. ...
Article
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Recent studies have greatly increased our knowledge of microbial ecology of the indoor environments in which we live and work. However, the number of studies collecting robust, long-term data using standardized methods to characterize important building characteristics, indoor environmental conditions, and human occupancy – collectively referred to as “built environment data” – remain limited. Insufficiently described built environment data can limit our ability to compare microbial ecology results from one indoor environment to another or to use the results to assess how best to control indoor microbial communities. This work first reviews recent literature on microbial community characterization in indoor environments (primarily those that utilized molecular methods), paying particular attention to the level of assessment of influential built environment characteristics and the specific methods and procedures that were used to collect those data. Based on those observations, we then describe a large suite of indoor environmental and building design and operational parameters that can be measured using standardized methods to inform experimental design in future studies of the microbial ecology of the built environment. This work builds upon the recently developed MIxS-BE package that identifies high-level minimal built environment metadata to collect in microbial ecology studies, primarily by providing more justification, detail, and context for these important parameters and others from the perspective of engineers and building scientists. It is our intent to provide microbial ecologists with knowledge of many of the tools available for built environment data collection, as well as some of the constraints and considerations for these tools, which may improve our ability to design indoor microbial ecology studies that can better inform building design and operation.
... They may also generate new pollutants such as ozone and other compounds derived from the ionization of VOCs. An ion generator installed in a 27 m 3 residential room by Waring and Siegel (2011) has increased concentrations of ultrafine particles (\0.1 lm), ozone, and to a lesser extent, the by-products of reactions initiated by ozone, such as aldehydes (formaldehyde and nonanal). ...
Article
Full-text available
Indoor air pollution is a complex issue involving a wide diversity and variability of pollutants that threats human health. In this context, major efforts should be made to enhance indoor air quality. Thus, it is important to start by the control of indoor pollution sources. Nevertheless, when the suppression or minimization of emission sources is insufficient, technically unfeasible, or economically unviable, abatement technologies have to be used. This review presents a general overview of single treatment techniques such as mechanical and electrical filtration, adsorption, ozonation, photolysis, photocatalytic oxidation, biological processes, and membrane separation. Since there is currently no technology that can be considered fully satisfactory for achieving “cleaner” indoor air, special attention is paid to combined purification technologies or innovative alternatives that are currently under research and have not yet been commercialized (plasma-catalytic hybrid systems, hybrid ozonation systems, biofilter-adsorption systems, etc.). These systems seem to be a good opportunity as they integrate synergetic advantages to achieve good indoor air quality.
... Apart from that, reactions between ozone and indoor chemical compounds yield a variety of harmful and irritating secondary pollutants (Weschler et al. 1992;Fan et al. 2003;Singer et al. 2006). Reactions between ozone and unsaturated volatile organic compounds (VOCs) can lead to formation of secondary organic aerosols (SOA), most of which are in the size range of fine and ultrafine particles (Weschler and Shields 1999;Wainman et al. 2000;Singer et al. 2006;Waring et al. 2008;Waring and Siegel 2011). SOA formation can undermine particle removal effects of wearable ionization air cleaners. ...
Article
Wearable ionization air cleaners are compact in size and marketed for personal respiratory protection by removing air pollutants from users' breathing zone. In this study, ozone emission and particle removal rates of four wearable ionization air cleaners (namely, AC1 through AC4) were evaluated inside a 0.46 m3 stainless steel chamber. Continuous measurements were conducted for ozone concentration, PM2.5 concentration and particle size distribution in the size range of 18.1–289 nm. Two of the four wearable air cleaners (i.e., AC1 and AC2) had detectable ozone emissions. The 10-hour average ozone emission rates were quite different (i.e., 0.67 mg·h−1 for AC1 and 3.40×10−2 mg·h−1 for AC2); however, the ozone emissions were negligible for AC3 and AC4. The number removal rates for particles within the measured size range were highly variable (i.e., 2.20 h−1, 0.52 h−1, 8.10 h−1, and 27.9 h−1 for AC1 through AC4, respectively). The corresponding mass removal rates of PM2.5 were 1.85 h−1, 0.48 h−1, 1.52 h−1 and 5.37 h−1, respectively. Regulatory guidelines are needed to assure these devices can effectively remove particles without ozone emissions to protect public health.
... In addition, the filters can become clogged over time, and so require regular cleaning. Generally speaking, electronic filters can generate hazardous charged particles [56] or new pollutants such as ozone, ultrafine particles and other compounds derived from VOCs ionization [57]. ...
Article
Full-text available
Aims: Indoor air quality (IAQ) has attracted increased attention with the emergence of COVID-19. Ventilation is perhaps the area in which the most changes have been proposed in response to the emergency caused by this virus. However, other strategies are possible, such as source control and the extraction of pollutants. The latter incorporates clean technologies, an emergent area with respect to IAQ. Method: Various air treatment technologies can be used to control contaminants, which are reviewed and discussed in this work, including physicochemical technologies (e.g., filtration, adsorption, UV-photocatalytic oxidation, ultraviolet disinfection and ionization) and biological technologies (e.g., plant purification methods and microalgae-based methods). Results and interpretation: This work reviews currently available solutions and technologies for “cleaning” indoor air, with a focus on their advantages and disadvantages. One of the most common problems in this area is the emission of pollutants that are sometimes more dangerous to human health than those that the technologies were developed to remove. Another aspect to consider is the limitation of each technology in relation to the type of pollutants that need to be removed. Each of the investigated technologies works well for a family of pollutants with similar characteristics, but it is not applicable to all pollutant types. Thus, the optimal solution may involve the use of a combination of technologies to extend the scope of application, in addition to the development of new materials, for example, through the use of nanotechnology.
... Besides, NAIs may emit ozone, which reacts with terpenoids to produce ultrafine secondary organic aerosols, carbonyls, carboxylic acids, and free radicals. Waring and Siegel [18] demonstrated that in a residential room the simultaneous use of the air ionizer and the air freshener (with terpenoids) resulted in increases in ultrafine particles, as well as formaldehyde and nonanal. ...
Article
A negative air ionizer (NAI) is a common indoor air purifier for aerosol particles. The turbulence intensity can influence the performance of NAI. Besides, the dielectric constants (p) of particles can affect the electric mobility and deposition of particles in the electric field. Hence, this study aims to exam the difference between the deposition rate of NaCl (p = 6.1) and sucrose (p = 3.3) submicron particles when an NAI is operating under various turbulence intensities. The experiments were conducted in a stainless steel chamber under 50% relative humidity. Polydisperse submicron particles (PSPs) of 30–300 nm and monodisperse submicron particles (MSPs) of 30, 50, 100, 170 and 300 nm were used for testing. In the experiments of particle deposition, the aerosol particle number concentration and size distribution were monitored continuously by a Scanning Mobility Particle Sizer. The decay constant of particle concentration (k) and effective cleaning rate (ECR) were determined from the time profiles of particle concentration. When the NAI was off, k of NaCl and sucrose particles was similar. However, when the NAI was operating, the deposition rate of NaCl particles was higher than that of sucrose particles and the NAI performed better under lower turbulence intensity. Because the coagulation coefficient of PSP was larger than MSP, the decay constant of PSP was superior to that of MSP. The ECR was negatively correlated with particle size and was higher under lower turbulence intensity. Conclusively, the NAI is more efficient in charging particles with higher dielectric constants and performance better under lower turbulence intensity.
... Air ions have a primary role in the discipline of atmospheric electricity, because their motion in the atmosphere serves the air conductivity (Wilson, 1924;Israël, 1970;Tinsley, 2008). Air ions have also raised the 20 interest of aerosol scientists because of their participation in atmospheric aerosol formation and thus their influences on air quality, human health and climate (Gunn, 1954;Bricard et al., 1968;Hõrrak et al., 1998;Yu and Turco, 2008;Manninen et al., 2010;Waring and Siegel, 2011). ...
Article
Full-text available
An Air Ion Spectrometer (AIS) was deployed for the first time at the Concordia station at Dome C (75°06’ S, 123°23’ E; 3220 m above sea level), Antarctica during 22 December 2010–16 November 2011 for measuring the number size distribution of air ions. In this work, we present results obtained from this air ion dataset together with aerosol particle and meteorological data. The main processes that modify the number size distribution of air ions during the measurement period at this high-altitude site included new particle formation (NPF, observed on 85 days), wind-induced ion formation (observed on 36 days), and ion production and loss associated with cloud/fog formation (observed on 2 days). On days without observations of the foregoing processes or other anomalies, i.e. event-free days, the concentration of cluster ions (0.9–1.9 nm) exhibited a clear seasonality, with high concentrations in the warm months and low concentrations in the cold. Compared to event-free days, days with NPF were observed with higher cluster ion concentrations. A number of NPF events were observed with restricted growth below 10 nm, which were termed as suppressed NPF. There was another distinct feature, namely a simultaneous presence of two or three separate NPF and subsequent growth events, which were named as multi-mode NPF events. Growth rates (GRs) were determined using two methods: the appearance time method and the mode fitting method. The former method seemed to work better for the NPF events characterized by a fast particle GR, whereas the latter method usually worked better when the GR was slow. The formation rate of 2-nm positive ions (J2+) was calculated for all the NPF events for which a GR in the 2–3 nm size range could be determined. On average, J2+ was about 0.014 cm−3 s
... В воздухе СФП под влиянием ионизирующего излучения продуцировались легкие и тяжелые отрицательные, а также положительные аэроионы. Действующим фактором отрицательных ионов является ионизированный кислород, снижающий количество серотонина в тканях, ускоряя его ферментативное расщепление [5,6]. Среднее количество легких отрицательных аэроионов до начала сеанса солелечения составляло 802,33±62,69 ион/см 3 , легких положительных -509,33±37,17 ион/см 3 . ...
Article
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Background: One of the methods of comprehensive therapeutic effects on the human body is sylvinite therapy which has not been used in the treatment of inflammatory periodontal diseases at young age. Aims: Hygienic and clinical evaluation of the possible application of therapeutic factors of sylvinite devices in dentistry. Materials and methods: We conducted hygienic study of the basic physical factors of the internal environment of modern sylvinite structures (radiation background, aeroionization and aerosol environment, climate). The percentage of sylvine and halite in the sylvinite minerals was determined using color image analysis of the salt screen. The microbiological studies of the impact of the mineral sylvinite on the growth parameters of bacterial culture were performed. We examined 79 patients aged 20-25 years diagnosed with chronic generalized catarrhal gingivitis, 36 persons underwent treatment course in the salt structure. The evaluation of the dental status and the periodontal status was conducted using hygienic and periodontal indices. The duration of study was 4 years. Results: All participants who entered the study completed it. In the experimental sylvinite room formed food-grade, biodegradable internal environment (background radiation - 0,18±0,0027 μsv/h; LOA - 802,33±62,69 ion/cm³; RO - 509,33±37,17 ion/cm3; stable microclimate). We detected evidence of an inhibitory effect of the combination on Staphylococcus aureus. The use of a comprehensive dental program has improved the condition of periodontal tissues and careeradvantage tooth enamel (PMA and SBI fell of 80.8% and 75.5%; the reduction of the CPU - 67.7%; fuel and energy resources increased by 37%). Conclusions: The inclusion of sylvinite therapy in the complex treatment of patients with chronic generalized catarrhal gingivitis had a marked positive impact on the state of periodontal tissues and local immunity of the oral cavity.
... Bazı elektronik hava temizleyicileri foto-plazma yöntemiyle akciğerde tahrişe neden olabilen ozon üretebilmektedir. İyon üreterek iç ortam hava kalitesini iyileştirmeye yönelik cihazların iç ortamda terpen kaynağı olduğu durumda ultra ince partikül oluşumuna neden olduklarına yönelik sonuçlar laboratuvar ve ev ortamında yapılan çalışmalarda gösterilmiştir [7,8,9]. ...
Conference Paper
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Indoor air pollution is within the top five evironmental health risks. The best way to decrease this risk, is controlling the pollution sources and ventilate the area. If these precautions are inefficient, an aircleaning device can be beneficial. Air cleaning devices used in the indoor environment can be helpful to control the range of pollutants such as allergens, particulate matter, bioaerosols and odor. In this study, the results of the experimental studies are given in order to detect the antimicrobial efficiency of two different commercially available portable air-cleaning device which are produced for the remediation of indoor air quality by the process of the production of photo-plasma and free radicals. A addition to this, photoplasma device showed higher removal efficiencies of 32.5%, 17.4% and 9.3% for E. coli, S. aureus and A. baumannii respectively than free radical generator. Each devices showed the highest removal efficiency on S. aureus. 1m3, hermetically sealed, glass room model was used to represent the indoor area. Suspensions of the most frequent microorganisms which were seen in the indoor environment (Acinetobacter baumannii, Escherichia coli, Staphylococcus aureus) injected into the glass room model with the nebulizer system. In both the working and non-working conditions of the air-cleaning devices, bioaerosol samples were taken periodically from the glass room and the concentration change of the bacteria in the environment was monitored. According to the results, it was determined that both of air cleaning devices were effective in decreasing the concentration of microorganisms in the indoor air. In addition to this, photoplasma device showed higher removal efficiencies of 32.5%, 17.4% and 9.3% for E. coli, S. aureus and A. baumannii respectively than free radical generator. Each devices showed the highest removal efficiency on S. aureus.
... Besides clearly indicated, professional constructional renovation to remove and avoid moisture and microbiological growth (see below), for additional technical measures (air filter, dehumidifier), which are occasionally recommended (Mazur and Kim, 2006), there is only insufficient evidence due to lack of studies (Singh and Jaiswal, 2013). "Air purifier" with ionizers must be considered problematic, as they can produce ozone levels which are harmful to health (Hubbard et al., 2005;Waring and Siegel, 2011). Affected individuals themselves should respect the following recommendations: ...
Article
In April 2016, the German Society of Hygiene, Environmental Medicine and Preventative Medicine (Gesellschaft für Hygiene, Umweltmedizin und Präventivmedizin (GHUP)) together with other scientific medical societies, German and Austrian medical societies, physician unions and experts has provided an AWMF (Association of the Scientific Medical Societies) guideline ‘Medical diagnostics for indoor mold exposure’. This guideline shall help physicians to advise and treat patients exposed indoors to mold. Indoor mold growth is a potential health risk, even without a quantitative and/or causal association between the occurrence of individual mold species and health effects. Apart from the allergic bronchopulmonary aspergillosis (ABPA) and the mycoses caused by mold, there is only sufficient evidence for the following associations between moisture/mold damages and different health effects: Allergic respiratory diseases, asthma (manifestation, progression, exacerbation), allergic rhinitis, exogenous allergic alveolitis and respiratory tract infections/bronchitis. In comparison to other environmental allergens, the sensitizing potential of molds is estimated to be low. Recent studies show a prevalence of sensitization of 3-10% in the total population of Europe. The evidence for associations to mucous membrane irritation and atopic eczema (manifestation, progression, exacerbation) is classified as limited or suspected. Inadequate or insufficient evidence for an association is given for COPD, acute idiopathic pulmonary hemorrhage in children, rheumatism/arthritis, sarcoidosis, and cancer. The risk of infections from indoor molds is low for healthy individuals. Only molds that are capable to form toxins can cause intoxications. The environmental and growth conditions and especially the substrate determine whether toxin formation occurs, but indoor air concentrations are always very low. In the case of indoor moisture/mold damages, everyone can be affected by odor effects and/or impairment of well-being. Predisposing factors for odor effects can be given by genetic and hormonal influences, imprinting, context and adaptation effects. Predisposing factors for impairment of well-being are environmental concerns, anxieties, conditioning and attributions as well as a variety of diseases. Risk groups that must be protected are patients with immunosuppression and with mucoviscidosis (cystic fibrosis) with regard to infections and individuals with mucoviscidosis and asthma with regard to allergies. If an association between mold exposure and health effects is suspected, the medical diagnosis includes medical history, physical examination, conventional allergy diagnosis, and if indicated, provocation tests. For the treatment of mold infections, it is referred to the AWMF guidelines for diagnosis and treatment of invasive Aspergillus infections. Regarding mycotoxins, there are currently no validated test methods that could be used in clinical diagnostics. From the perspective of preventive medicine, it is important that mold damages cannot be tolerated in indoor environments.
... In that these devices do not possess collector plates, the charged particles attach to nearby surfaces or to one another forming heavier particles that promote deposition. Electronic air filtration is efficient at removing particles (90% and 95% for 0.3-6 μm particles for electrostatic filters and ion generators respectively) and results in slower pressure loss than mechanical filters, however a high relative humidity can negatively affect removal efficiency, plus they can generate hazardous charged particles and unwanted oxidation byproducts (Guieysse et al., 2008;Waring and Siegel, 2011). ...
Article
In today's ‘indoor generation’ most human activities take place within an enclosed space, characterised by a chemically diverse and complex air quality. Although source control is the universally preferred approach to reduce contaminants, this is becoming increasingly insufficient, technically unfeasible or economically unviable. The provision of adequate ventilation is also being challenged by invariably poor outdoor air quality and our quest for a low carbon economy. Whilst the former directly adds to the burden of indoor air pollution, both factors attract mitigation measures that are leading to efforts to seal off indoor spaces, which can increase exposure to endogenous indoor air pollutants, heighten health risks and curtail concentration, learning and productivity. Research to date on the role of air purification technologies in key indoor microenvironments demonstrates that air filtration produces clear reductions in indoor pollution concentrations. To confirm the optimistic modelled health/performance benefits associated with air purification further research is required, evaluating longer term interventions particularly in vulnerable populations, employing real-time sensors to quantitatively assess complete exposure profiles and optimizing technologies/strategies to remove specific indoor air pollutants (eg infiltrated versus endogenous particles, gases, chemically transformed organics) within the unique spaces where people live, learn, work and travel.
... Also, VOCs take part in sec-ondary organic aerosol (SOA) formation in indoor air and thus exacerbates occupant exposure to undesirable air pollutants. Several air cleaning technologies have been studied in the past for VOC abatement, i.e., adsorption, non-thermal plasma, ozonation, ultraviolet germicidal irradiation, etc. [2,3,4]. While adsorption, the typically used technology for VOC removal requires regular filter replacement, advanced oxidation processes such as photocatalytic oxidation (PCO) completely mineralize organic pollutants rather than accumulating them and hence has a longer lifetime. ...
... However, negative ion-based systems produce significant amounts of ozone, so they should be avoided in enclosed spaces. 169 Wang 170 showed that the filtration efficiency increases as the particle size decreases down to 2-3 nm. However, one of the key parameters in characterizing the risks to which people can be exposed is particle diameter, 168 and the filtration of non-spherical particles, such as e.g. ...
Article
Nanoparticles containing metals in their structure constitute an increasingly large group of substances present in the air. They come from both natural and anthropogenic sources. The wider and wider use of such particles means that increasingly complicated structures are present in the air we breathe. These particles are in the ultrafine size range (<100 nm), readily deposit in the lower areas of the respiratory tract and can be translocated directly into our body. Therefore, it is necessary to know their properties, impacts on the environment, effects on human health, and methods of protection against them, including the possibility of using modern forecasting tools such as mathematical models.
... They observed pre-ozonation emission rates from aired samples that were greater than pre-ozonation emission rates from stored samples. Waring and Siegel (2011) also measured carbonyl emissions in a room containing carpet with ozone and found increased levels of formaldehyde and nonanal. ...
Article
Abstract The health effects associated with exposure to ozone range from respiratory irritation to increased mortality. In this paper, we explore the use of three green building materials and an activated carbon (AC) mat that remove ozone from indoor air. We studied the effects of long-term exposure of these materials to real environments on ozone removal capability and pre- and post-ozonation emissions. A field study was completed over a 6-month period, and laboratory testing was intermittently conducted on material samples retrieved from the field. The results show sustained ozone removal for all materials except recycled carpet, with greatest ozone deposition velocity for AC mat (2.5–3.8 m/h) and perlite-based ceiling tile (2.2–3.2 m/h). Carbonyl emission rates were low for AC across all field sites. Painted gypsum wallboard and perlite-based ceiling tile had similar overall emission rates over the 6-month period, while carpet had large initial emission rates of undesirable by-products that decayed rapidly but remained high compared with other materials. This study confirms that AC mats and perlite-based ceiling tile are viable surfaces for inclusion in buildings to remove ozone without generating undesirable by-products. The use of passive removal materials for ozone control could decrease the need for, or even render unnecessary, active but energy consuming control solutions. In buildings where ozone should be controlled (high outdoor ozone concentrations, sensitive populations), materials specifically designed or selected for removing ozone could be implemented, as long as ozone removal is not associated with large emissions of harmful by-products. We find that activated carbon mats and perlite-based ceiling tiles can provide substantial, long-lasting, ozone control.
... 27 Several types of air puriers can increase indoor O 3 levels, either deliberately (e.g., O 3 generators) or as a byproduct of their operation (e.g., ion generators, electrostatic precipitators, and some UV-lamp containing air cleaners). [28][29][30] Specic devices may emit oxidants other than O 3 . 31 Most emission sources are constrained only to select chemicals (e.g. ...
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The chemistry of oxidants and their precursors (oxidants*) plays a central role in outdoor environments but its importance in indoor air remains poorly understood. Ozone (O3) chemistry is important in some indoor environments and, until recently, ozone was thought to be the dominant oxidant indoors. There is now evidence that formation of the hydroxyl radical by photolysis of nitrous acid (HONO) and formaldehyde (HCHO) may be important indoors. In the past few years, high time-resolution measurements of oxidants* indoors have become more common and the importance of event-based release of oxidants* during activities such as cleaning has been proposed. Here we review the current understanding of oxidants* indoors, including drivers of the formation and loss of oxidants*, levels of oxidants* in indoor environments, and important directions for future research.
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Through both air inhalation, dust injestion and dermal exposure, the indoor environment plays an important role in controlling human chemical exposure. Indoor emissions and chemistry can also have direct impacts on the quality of outdoor air. And so, it is important to have a strong fundamental knowledge of the chemical processes that occur in indoor environments. This review article summarizes our understanding of the indoor chemistry field. Using a molecular perspective, it addresses primarily the new advances that have occurred in the past decade or so and upon developments in our understanding of multiphase partitioning and reactions. A primary goal of the article is to contrast indoor chemistry to that which occurs outdoors, which we know to be a strongly gas-phase, oxidant-driven system in which substantial oxidative aging of gases and aerosol particles occurs. By contrast, indoor environments are dark, gas-phase oxidant concentrations are relatively low, and due to air exchange, only short times are available for reactive processing of gaseous and particle constituents. However, important gas-surface partitioning and reactive multiphase chemistry occur in the large surface reservoirs that prevail in all indoor environments. These interactions not only play a crucial role in controlling the composition of indoor surfaces but also the surrounding gases and aerosol particles, thus affecting human chemical exposure. There are rich research opportunities available if the advanced measurement and modeling tools of the outdoor atmospheric chemistry community continue to be brought indoors.
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Just as the chemistry creates urban smog and aerosols that influence climate change, chemistry in building air can alter the indoor environment for better or worse. This review focuses on chemical pathways initiated by oxidants that infiltrate from outdoor air and other indoor-sourced reactants and surfaces that make these environments unique chemical reactors. Ozone reacts with fragrance molecules, tobacco smoke residues, and even human skin oils to generate a host of oxidized organic compounds, secondary organic aerosols, and irritants. Nitrous acid is formed on indoor surfaces and is subsequently cleaved by even the relatively dim light indoor. This raises the indoor concentration of the highly reactive hydroxyl radical. Nitrous acid can also react with tobacco smoke residue to form carcinogenic nitrosamines. Some seek to harness this chemistry to help reduce indoor concentrations of unwanted indoor pollutants using novel surface coatings, but controlling that chemistry is challenging.
Article
The ozonolysis of terpenoids generates secondary organic aerosol (SOA) indoors. Models of varying complexity have been used to predict indoor SOA formation, and many models use the SOA yield, which is the ratio of the mass of produced SOA and the mass of consumed reactive organic gas. For indoor simulations, the SOA yield has been assumed as a constant, even though it depends on the concentration of organic particles in the air, including any formed SOA. We developed two indoor SOA formation models for single terpenoid ozonolysis, with yields that vary with the organic particle concentration. The models have their own strengths and were in agreement with published experiments for d-limonene ozonolysis. Monte Carlo analyses were performed, which simulated different residential and office environments to estimate ranges of SOA concentrations and yields for d-limonene and α-pinene ozonolysis occurring indoors. Results indicate that yields are highly variable indoors and are most influenced by background organic particles for steady-state formation and indoor ozone concentration for transient peak formation. Additionally, a review of ozonolysis yields for indoor-relevant terpenoids in the literature revealed much uncertainty in their values at low concentrations typical of indoors. The results in this study suggest important factors that govern indoor secondary organic aerosol (SOA) formation and yields, in typical residential and office spaces. This knowledge informs the development and comparison of control strategies to reduce indoor-generated SOA. The ranges of SOA concentrations predicted indoors allow the quantification of the effects of sorptive interactions of semi-volatile organic compounds or reactive oxygen species with SOA, filter loading owing to SOA formation, and impacts of SOA on health, if links are established.
Article
Reactions between ozone and terpenoids produce numerous products, some of which may form secondary organic aerosol (SOA). This work investigated the contribution to gas-phase SOA formation of ozone reactions with surface-sorbed d-limonene, which is common indoors. A model framework was developed to predict SOA mass formation because of ozone/terpenoid surface reactions, and it was used with steady state experiments in a 283 L chamber to determine the aerosol mass fraction of SOA resulting from surface reactions, ξs (the ratio of mass of SOA formed and mass of ozone consumed by ozone/terpenoid surface reactions), for ozone/d-limonene reactions on stainless steel. The ξs = 0.70-0.91, with lower relative humidity leading to both higher mass and number formation. Also, surface reactions promoted nucleation more than gas-phase reactions, and number formation due to surface reactions and gas-phase reactions were 126-339 and 51.1-60.2 no./cm(3) per μg/m(3) of formed SOA, respectively. We also used the model framework to predict that indoor spaces in which ozone/d-limonene surface reactions would likely lead to meaningful gas-phase SOA formation are those with surfaces that have low original reactivity with ozone, such as glass, sealed materials, or smooth metals.
Article
Ozone reacts with indoor-emitted terpenoids to form secondary organic aerosol (SOA). Most SOA research has focused on ozone reactions with single terpenoids or with consumer products, and this paper reports the results from an investigation of SOA formation from ozone reactions with both single terpenoids and mixtures of d-limonene, α-pinene, and α-terpineol. Transient experiments were conducted at low (25 ppb) and high (100 ppb) initial concentrations of ozone. The three terpenoids were tested singly and in combinations in a manner that controlled for their different reaction rates with ozone. The SOA formation was assessed by examining the evolution in time of the resulting number size-distributions and estimates of the mass concentrations. The results suggest that at higher ozone and terpenoid concentrations, SOA number formation follows a linear trend as a function of the initial rate of reaction. This finding was valid for both single terpenoids and mixtures. Generally speaking, higher ozone and terpenoid concentrations also led to larger geometric mean diameters and smaller geometric standard deviations of fitted lognormal distributions of the formed SOA. By assuming a density, mass concentrations were also assessed and did not follow as consistent of a trend. At low ozone concentration conditions, reactions with only d-limonene yielded the largest number concentrations of any experiment, even more than experiments with mixtures containing d-limonene and much higher overall terpenoid concentrations. This finding was not seen for high ozone concentrations. These experiments demonstrate quantifiable trends for SOA forming reactions of ozone and mixtures, and this work provides a framework for expanding these results to more complex mixtures and consumer products.
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Since late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread globally, causing a pandemic (coronavirus disease 2019, or COVID-19) with dire consequences, including widespread death, long-term illness, and societal and economic disruption. Although initially uncertain, evidence is now overwhelming that SARS-CoV-2 is transmitted primarily through small respiratory droplets and aerosols emitted by infected individuals. As a result, many effective nonpharmaceutical interventions for slowing virus transmission operate by blocking, filtering, or diluting respiratory aerosol, particularly in indoor environments. In this review, we discuss the evidence for airborne transmission of SARS-CoV-2 and implications for engineering solutions to reduce transmission risk. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 13 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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The purpose of this paper is to identify potential human health concerns that may arise from the increasing popularity of zero net energy homes (ZNEH) a form of high-performance green building in the US. Since high levels of energy consumption are not sustainable, ZNEH has the potential to reduce the environmental impact without penalty to occupants by providing a healthy home environment at low energy inputs. The premise of this article is that ZNEHs can indeed maintain high levels of health while reducing energy consumption. However, the potential for health impacts must be investigated. In this brief essay, main health questions that might arise in relationship to ZNEHs are reviewed. In addition, potential areas for additional research on zero net energy homes and their effects on human health are identified. This topic remains in its infancy and is a viable area of research that will benefit greatly from additional research.
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Unlabelled: Ultrafine particle (UFP) emissions from three essential-oil-based mosquito repellent products (lemon eucalyptus (LE), natural insects (NI), and bite shield (BS)) were tested in a 386 l chamber at a high air exchange rate of 24/h with filtered laboratory air. Total particle number concentration and size distribution were monitored by a condensation particle counter and a scanning mobility particle sizer, respectively. UFPs were emitted from all three products under indoor relevant ozone concentrations (~ 17 ppb). LE showed a nucleation burst followed by a relatively stable and continuous emission while the other two products (NI and BS) showed episodic emissions. The estimated maximum particle emission rate varied from 5.4 × 10(9) to 1.2 × 10(12) particles/min and was directly related to the dose of mosquito repellent used. These rates are comparable to those due to other indoor activities such as cooking and printing. The emission duration for LE lasted for 8-78 min depending on the dose applied while the emission duration for NI and BS lasted for 2-3 h. Practical implications: Certain essential-oil-based mosquito repellents can produce high concentrations of UFPs when applied, even at low ozone levels. Household and personal care products that contain essential oil may need to be tested at indoor relevant ozone levels to determine their potential to increase personal UFP exposures.
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The COVID-19 pandemic increased the demand for indoor air cleaners. While some commercial electronic air cleaners can be effective in reducing primary pollutants and inactivating bioaerosol, studies on the formation of secondary products from oxidation chemistry during their use are limited. Here, we measured oxygenated volatile organic compounds (OVOCs) and the chemical composition of particles generated from a hydroxyl radical generator in an office. During operation, enhancements in OVOCs, especially low-molecular-weight organic acids, were detected. Rapid increases in particle number and mass concentrations were observed, corresponding to the formation of highly oxidized secondary organic aerosol (SOA) (O:C ∼ 1.3), with an enhanced signal at m/z 44 (CO2⁺) in the organic mass spectra. These results suggest that organic acids generated during VOC oxidation contributed to particle nucleation and SOA formation. Nitrate, sulfate, and chloride also increased during the oxidation without a corresponding increase in ammonium, suggesting organic nitrate, organic sulfate, and organic chloride formation. As secondary species are reported to have detrimental health effects, further studies should not be limited to the inactivation of bioaerosol or reduction of particular VOCs, but should also evaluate potential OVOCs and SOA formation from electronic air cleaners in different indoor environments.
Chapter
This chapter applies additional attributes of material environmental sciences in previous chapters to emerging material sciences. It seeks organization forms for Mark II firms that facilitate their emergence and contribution to variety through inductive-deductive analysis. Based on Saviotti and Metcalfe in Research Policy 13:141–151 (1984), the processes of substitution, specialization, and emergence of new products can be the essential components of more complex processes in the real economies. The variety and productivity growth complement each other (Saviotti in Technological evolution, variety and the economy. Edward Elgar, Cheltenham, 1996). If growing productivity can liberate the resources necessary to generate new commodities, this condition increases a variety of technology, products, and services. In either case of productivity growth or specialization, some organizational mechanisms are necessary to develop a net variety. Organizations can reduce the process variety in achieving a given output variety (see, Saviotti, 1996). This chapter then suggests a design that simultaneously achieves the process of variety reduction and reconfiguration.
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Air cleaning is broadly applied to reduce contaminant concentrations in many buildings. Although diverse in underlying technology, mode of application, target contaminants, and effectiveness, there are also commonalities in the framework for understanding their primary impact (i.e., concentration reductions) and secondary impacts (e.g., energy use, byproduct production). Furthermore, both primary and secondary impacts are moderated by the specific indoor context in which an air cleaner is used. This paper explores the dynamics of removal efficiency in a variety of air cleaners and combines efficiency and flow rate to put air cleaning in the context of real indoor environments. This allows for the direct comparison to other indoor pollutant loss mechanisms (ventilation and deposition) and further suggests that effective air cleaner use is context- and contaminant-specific. The concentration reduction impacts of air cleaning need to be contrasted with the secondary consequences that arise from the use of air cleaners. This paper emphasizes two important secondary consequences: energy use of the air cleaning process and primary and secondary emissions from air cleaners. The paper also identifies current research challenges and areas for large leaps in our understanding of the role of air cleaners in improving indoor environmental quality. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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Ozonation is a common remediation approach to eliminate odors from mold, tobacco and fire damage in buildings. Little information exists to: 1) assess its effectiveness; 2) provide guidance on operation conditions; and 3) identify potential risks associated with the presence of indoor ozone and ozonation byproducts. The goal of this study is to evaluate chemical changes in thirdhand smoke (THS) aerosols induced by high levels of ozone, in comparison with THS aerosols aged under similar conditions in the absence of ozone. Samples representing different stages of smoke aging in the absence of ozone, including freshly emitted secondhand smoke (SHS) and THS, were collected inside an 18-m³ room-sized chamber over a period of 42 h after six cigarettes were consumed. The experiments involved collection and analysis of gas phase species including volatile organic compounds (VOCs), volatile carbonyls, semivolatile organic compounds (SVOCs), and particulate matter. VOC analysis was carried out by gas chromatography/mass spectrometry with a thermal desorption inlet (TD-GC/MS), and volatile carbonyls were analyzed by on-line derivatization with dinitrophenylhydrazine (DNPH), followed by liquid chromatography with UV/VIS detection. SVOCs were extracted from XAD-coated denuders and Teflon-coated fiberglass filters in the absence of ozone. In those extracts, tobacco-specific nitrosamines (TSNAs) and other SVOCs were analyzed by gas chromatography with positive chemical ionization-triple quadrupole mass spectrometric detection (GC/PCI-QQQ-MS), and polycyclic aromatic hydrocarbons (PAHs) were quantified by gas chromatography with ion trap mass spectrometric detection (GC/IT-MS) in selected ion monitoring mode. Particulate matter concentration was determined gravimetrically. In a second experiment, a 300 mg h⁻¹ commercial ozone generator was operated during 1 h, one day after smoke was generated, to evaluate the remediation of THS by ozonation. VOCs and volatile carbonyls were analyzed before and after ozonation. Extracts from fabrics that were exposed in the chamber before and after ozonation as surrogates for indoor furnishings were analyzed by GC/IT-MS, and aerosol size distribution was studied with a scanning mobility particle sizer. Ozone concentration was measured with a photometric detector. An estimated 175 mg ozone reacted with THS after 1 h of treatment, corresponding to 58% of the total O3 released during that period. Fabric-bound nicotine was depleted after ozonation, and the surface concentration of PAHs adsorbed to fabric specimens decreased by an order of magnitude due to reaction with ozone, reaching pre-smoking levels. These results suggest that ozonation has the potential to remove harmful THS chemicals from indoor surfaces. However, gas phase concentrations of volatile carbonyls, including formaldehyde, acetaldehyde and acetone were higher immediately after ozonation. Ultrafine particles (UFP, in most cases with size <60 nm) were a major ozonation byproduct. UFP number concentrations peaked shortly after ozonation ended, and remained at higher-than background levels for several hours. Based on these results, minimum re-entry times after ozone treatment were predicted for different indoor scenarios. Clearly defining re-entry times can serve as a practical measure to prevent acute exposures to ozone and harmful ozonation byproducts after treatment. This study evaluated potential benefits and risks associated with THS remediation using ozone, providing insights into this technology.
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There is a need of the solution of two inconsistent tasks connected with features of technical characteristics assignment when using electrical corona air ionizers for correction of air ion composition. On the one hand, for providing sufficient generating ability of the air ionizer the increasing of corona voltage is necessary. On the other hand, increase of the corona voltage leads to increasing in generation of concomitant harmful chemical compounds.Results of research of small air ion concentration and volume concentration of ozone O3, nitrogen oxide NO and nitrogen oxides (in terms of NO2) are presented.The received empirical dependences allow to carry out calculating of change of foregoing above characteristics for formed air ion composition.
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Previous research has shown that ozone reactions on surface-sorbed d-limonene can promote gas phase secondary organic aerosol (SOA) formation indoors. In this work, we conducted 13 steady state chamber experiments to measure the SOA formation entirely initiated by ozone reactions with squalene sorbed to glass, at chamber ozone of 57-500ppb for two relative humidity (RH) conditions of 21% and 51%, in the absence of seed particles. Squalene is a nonvolatile compound that is a component of human skin oil and prevalent on indoor surfaces and in settled dust due to desquamation. The size distributions, mass and number secondary emission rates (SER), aerosol mass fractions (AMF), and aerosol number fractions (ANF) of formed SOA were quantified. The surface AMF and ANF are defined as the change in SOA mass or number formed, respectively, per ozone mass consumed by ozone-squalene reactions. All experiments but one exhibited nucleation and mass formation. Mass formation was relatively small in magnitude and increased with ozone, most notably for the RH=51% experiments. The surface AMF was a function of the chamber aerosol concentration, and a multi-product model was fit using the 'volatility basis set' framework. Number formation was relatively strong at low ozone and low RH conditions. Though we cannot extrapolate our results because experiments were conducted at high air exchange rates, we speculate that this process may enhance particle number more than mass concentrations indoors.
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This study evaluated the effectiveness of 30 or 60min of daily exposure to high-density or to zero-density (placebo condition) negative air ions over 18 days on the symptoms of seasonal affective disorder (SAD) in 40 participants under controlled laboratory conditions. Exposure to high-density negative air ions was superior to zero-density negative air ions in alleviating depression and the atypical symptoms of SAD. Also, more subjects in the high-density negative air ions groups met two different clinical response criteria than did those in the zero-density groups. Within the high density treatment group, both the short and long daily exposure reduced SAD symptoms. Exposure to negative air ions produced no negative side effects, and no ozone was produced by the ion generators. In both the high-density negative air ions and zero-density negative air ions groups, a significant placebo effect was found for most clinical measures. Finally, for the high-density negative air ion groups, subjects with a morningness chronotype responded better to treatment with high-density negative air ions than did those with an eveningness chronotype.
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Presence of ozone in indoor environment has implications on creation of sustainable indoor environment. A material mass balance model is used to summarize outcome of the review exercise that was conducted to understand what 15 years has taught us, with regards to the chemistry and concentration of ozone in indoor environment, since after a similar review effort by Weschler in the year 2000. Additionally, key knowledge gained on the impact of ozone and its initiated chemistry products on human health and comfort are summarized. This paper is concluded with recommendations for future research directions.
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This study investigates the spatial and temporal dispersion of particulate matter (PM) when using a needle-type electrostatic precipitator (ESP). The ESP is installed in tubes of 3 and 10 cm diameter. A simple light scattering setup integrated with image processing is built to evaluate and quantify the spatial and temporal dispersion of PM. The ESP is operated under stationary and continuous flowing modes to test its PM removal capability. Under the stationary mode, PM is removed efficiently in 10 and 45 seconds when using a 3 and 10 cm tube, respectively. In a more geometrically confined system, a large spatial particulate concentration gradient is seen from 18 to 24 cm, indicating that the cleaning capability can be controlled within a localized space. By modulating the applied voltage from direct current (DC) to a low-frequency pulse with 50% duty, the ozone concentration can be reduced by nearly 50% while maintaining the cleaning efficiency. The analysis with spatially and temporally resolved particulate dispersion provides a novel strategy for testing the performance of an ESP. Furthermore, physical confinement enhances both the spatial and temporal removal efficiency, which is crucial for indoor and personal air cleaning devices. These results will contribute to air purification and environmental monitoring.
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The improvement of the indoor air varies according to the type, source and dispersion pattern of the pollutant. Solution for reduction of pollutant exposure can be source control, as well as solution for reducing concentration and exposure only. Todey, there are many types of air cleaners available. The efficiency of the air purifiers varies depending on the air ratio and the air filtering capacity. Over the last decade, especially the use of desktop cleaners has increased. Indoor air purifiers can help control airborne allergens, particulate matter, bioaerosols, odor and gaseous pollutant levels. In this study, the effects of the removal particulate matter and formaldehyde by the Photo Plasma device, the radical generating portable air purifier and the air (purifier with water filter were investigated. The activities of the air cleaners in the indoor environment were observed by developing chamber test model. In the conditions where the air cleaning devices were both effective and not effective, air samples were taken at regular intervals from the glass reactor and changes in the particulate matter and formaldehyde concentration in the environment were monitored. According to the results, it was determined that the air cleaning devices examined were effective in decreasing the concentrations of particulate matter and formaldehyde in the indoor air, and the reduction efficiency varied according to the air purifier type.
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Aerosol diameter is important in determining its fate and transport. Indoors, the ozonolysis of terpenoids, such as limonene, yields secondary organic aerosol (SOA), which can range orders of magnitude in size. The generated SOA size distributions are affected by various processes, including nucleation, partitioning, coagulation, surface deposition, and air exchange; of these processes, only air exchange is not size resolved. Herein, a model was developed to predict the transient evolution of the SOA size distribution indoors due to limonene ozonolysis. The model simulates partitioning without requiring explicit knowledge of the chemical mechanism, because it instead combines the theory of the aerosol mass fraction (AMF = mass SOA formed/mass terpenoid reacted) with Fick's first law to predict the change in aerosol volume from SOA formation. We used experimental results for limonene ozonolysis from our previous work to evaluate and tune the model, and the model performed well according to standard indoor air quality model assessment methods. Its framework can be extended to other terpenoids, and its current form can be used to predict the implications of size resolved SOA formation due to ozonolysis of limonene, the most common indoor terpenoid. Further, a sensitivity analysis showed that air exchange could be one of the most influential mechanisms to control SOA indoors.
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Monoterpene is one class of biogenic volatile organic compounds (BVOCs) which widely presents in household cleaning products and air fresheners. It plays reactive role in secondary organic aerosols (SOAs) formation with ozone (O3) in indoor environments. Such ozonolysis can be influenced by the presence of gaseous pollutants such as ammonia (NH3). This study focuses on investigations of ozone-initiated formation of indoor SOAs with d-limonene, one of the most abundant indoor monoterpenes, in a large environmental chamber. The maximum total particle number concentration from the ozonolysis in the presence of NH3 was 60% higher than that in the absence of NH3. Both of the nuclei coagulation and condensation involve in the SOAs growth. The potential risks of pulmonary injury for the exposure to the secondary particles formed were presented with the indexes of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-10 (IL-10) expression levels in bronchoalveolar lavage fluid (BALF) upon intratracheal instillation in mice lung for 6 and 12 h. The results indicated that there was 22–39% stronger pulmonary inflammatory effect on the particles generated with NH3. This is a pilot study which demonstrates the toxicities of the indoor SOAs formed from the ozonolysis of a monoterpene.
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Population growth increasing life level and limitations of energy sources made efficient use of energy sources an inevitable task. The floor heating system has been developed as one of the most energy-efficient systems for heating inside spaces. The adoption of an energy-efficient heating system still requires the provision of acceptable indoor air quality to ensure a healthy environment. In this study, airborne particle distribution inside a space equipped separately with the radiator and floor heating systems is investigated experimentally. The experiments executed in an unoccupied residential room of 3m×4m×3m and sensitivity analyses were performed to unveil the effect of air temperature and floor cover on particle distribution pattern. The room space was divided into eight zones, where the particle concentration of PM2.5 and PM10 are measured by sampling the air. The results reveal that in radiator and floor heating systems, the highest airborne particle concentration is for PM10 and PM2.5 particles, respectively, which are 61% and 39% beyond their maximum allowable limit values. Between PM2.5 and PM10 particles, the concentration pattern of PM2.5 particles is more sensitive to change of both air temperature and floor condition. Also, between the radiator and floor heating system, the sensitivity is the highest in case of using floor heating system. By comparing the total deviation of PM2.5 and PM10 particle concentration from their corresponding allowable limit, the floor heating system is proposed as a more healthy heating system.
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The paper deals with ionization impact on efficient cleaning of air in a measuring chamber which has been cleaned and closed against any outer impacts (e.g. impurities, dust from another room, human odours). Smoking has an impact on the number of positive and negative ions including the concentration of particulate matter PM10. We investigated the ion concentration according to the presence of cigarette smoke in the room and according to the change of lit cigarette distance from the supply of ionized air. Due to the experiment there was simulated smoking at the relative air humidity φ = 37 % and φ = 39 % and temperature of 20 °C in the room. Increased PM10 concentrations were caused only by cigarette smoke pollution or more precisely by artificially created higher humidity in the measuring room excluding ambient environment impacts. The aim of the experiments was to prove influence of ionization on the elimination of cigarette smoke. The measurements showed that the highest efficiency of PM10 particulate removal was achieved when the distance of smoking cigarettes from ionization source was 3 m and the air humidity was 39 %. The consequent increase of the distance of smoking cigarettes from the ionization source significantly decreased the efficiency of particle removal. The difference between ionized and natural air is minimal at the bigger distance.
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Cited By (since 1996): 63 , Export Date: 4 February 2013 , Source: Scopus , The following values have no corresponding Zotero field: Author Address: EPRI, 3412 Hillview Avenue, Palo Alto, CA 94304-1395, United States Author Address: UMDNJ/R. W. J. Med. Sch./Rutgers, Department of Environmental Medicine, Piscataway, NJ, United States Author Address: Harvard School of Public Health, Department of Environmental Health, Landmark Center, Boston, MA, United States
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The associations between ozone concentrations measured outdoors and both morbidity and mortality may be partially due to indoor exposures to ozone and ozone-initiated oxidation products. In this article I examine the contributions of such indoor exposures to overall ozone-related health effects by extensive review of the literature as well as further analyses of published data. Daily inhalation intakes of indoor ozone (micrograms per day) are estimated to be between 25 and 60% of total daily ozone intake. This is especially noteworthy in light of recent work indicating little, if any, threshold for ozone's impact on mortality. Additionally, the present study estimates that average daily indoor intakes of ozone oxidation products are roughly one-third to twice the indoor inhalation intake of ozone alone. Some of these oxidation products are known or suspected to adversely affect human health (e.g., formaldehyde, acrolein, hydroperoxides, fine and ultrafine particles). Indirect evidence supports connections between morbidity/mortality and exposures to indoor ozone and its oxidation products. For example, cities with stronger associations between outdoor ozone and mortality tend to have residences that are older and less likely to have central air conditioning, which implies greater transport of ozone from outdoors to indoors. Indoor exposures to ozone and its oxidation products can be reduced by filtering ozone from ventilation air and limiting the indoor use of products and materials whose emissions react with ozone. Such steps might be especially valuable in schools, hospitals, and childcare centers in regions that routinely experience elevated outdoor ozone concentrations.
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The objective of this study was to test the effectiveness of individual commercially available portable indoor air cleaning units in removing dust particulates, tobacco smoke particulate and vapor phase constituents (nicotine and vinyl pyridine), viable and total fungal spores, pollen, and gaseous contaminants (carbon monoxide[CO], nitrogen dioxide[NO2], and formaldehyde[HCHO]), in a clean air test chamber. The air cleaner chamber results presented here represent initial-use results. In general, High Efficiency Particulate Air (HEPA) and electrostatic precipitator systems demonstrated the highest efficiencies with respect to particulate, contaminants, followed closely by electret filter systems. Ionizers and ozone generators were least effective in particulate removal. Systems which included sufficient sorbent material (i.e. activated carbon or potassium permanganate) were marginally effective at gaseous contaminant removal. None of the systems tested were effective at carbon monoxide removal. Sensory testing was conducted to discern potential correlation between human perceptive response and measured air cleaner performance (with respect to tobacco smoke removal). An electret filter (EF) loaded with carbon sorbent received the best ratings with respect to odor strength, nasal irritation, eye irritation, and overall air acceptability.
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Efforts to understand and mitigate the health effects of particulate matter (PM) air pollution have a rich and interesting history. This review focuses on six substantial lines of research that have been pursued since 1997 that have helped elucidate our understanding about the effects of PM on human health. There has been substantial progress in the evaluation of PM health effects at different timescales of exposure and in the exploration of the shape of the concentration-response function. There has also been emerging evidence of PM-related cardiovascular health effects and growing knowledge regarding interconnected general pathophysiological pathways that link PM exposure with cardiopulmonary morbidity and mortality. Despite important gaps in scientific knowledge and continued reasons for some skepticism, a comprehensive evaluation of the research findings provides persuasive evidence that exposure to fine particulate air pollution has adverse effects on cardiopulmonary health. Although much of this research has been motivated by environmental public health policy, these results have important scientific, medical, and public health implications that are broader than debates over legally mandated air quality standards.
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A conservative assessment suggests that over 1% of homes in the U.S. use ionizing air cleaners. Ion generators use charged plates to remove oppositely-charged particles and often generate ozone as a byproduct of their operation. In the present paper, five commercially available ionizing air cleaners were evaluated and compared to a portable HEPA filter and dedicated ozone generator. Air flow rate, ozone emission rate, and size resolved (0.1 - 1 µm) clean air delivery rate (CADR) were measured in a stainless steel test chamber for each cleaner. The air flow rates ranged from less than 30 m3/hr to 75 m3/hr, about an order of magnitude lower than a portable HEPA filter. Ozone emission rates were 0.7 - 4.1 mg/hr, about an order of magnitude lower than a dedicated ozone generator. Although the ozone emission rates for ion generators were low, they still may represent a health concern. The ionizing air cleaners remove submicron particles with CADRs ranging from 8 - 82 (m 3 /hr), considerably lower than the 200 - 250 m3/hr range for the tested HEPA air filter. These results allow for a more complete analysis of the positive and negative indoor air quality impacts of portable ion generators.
Article
Indoor air quality problems resulting from emission of volatile organic compounds (VOCs) have become an issue of increasing concern. Factors known to affect VOC levels in indoor air include: ventilation rate, occupant activities, and emissions from building and furnishing materials. In this research, VOC emissions from particleboard and medium density fiberboard (MDF) were measured in small stainless steel chambers (53 L) during a 4-day period. A protocol was developed to obtain new and representative samples and to minimize contamination of the samples during collection, preparation, and shipment to the laboratory. Samples were collected from 53 of the 61 U.S. mills that produce particleboard and MDF. Each mill identified the predominant tree species used to manufacture the panels. The laboratory tests were conducted at 45 percent relative humidity and used a gas chromatograph and a mass selective detector to identify and quantify VOC compounds. The predominant compounds identified in emissions from the particleboard and MDF samples were terpenes and aldehydes. Small straight-chain alcohols and ketones were also found. This study describes the terpene emission data. Quantified terpenes included α- and β-pinene, camphene, 3-carene, p-cymene, limonene, and borneol. Terpene emissions accounted for between 7 and 21 percent of the total VOC emissions, calculated as α-pinene. The highest terpene emissions were observed from particleboard samples manufactured from pines other than southern pine. For particleboard, terpene emissions were largely related to the extractive content of the wood species. The terpenes were almost completely absent in emissions from MDF samples, which indicates that differences in the manufacturing of MDF compared with the manufacturing of particleboard may have considerably affected emissions. After 4 days, the terpene emissions from all particleboard samples decreased to between 20 and 70 percent of their initial values.
Article
Field experiments were conducted in four homes during summerto quantify ozone-induced secondary emission rates (SERs) of aldehydes on indoor surfaces. Four surfaces in each house were examined: living room carpet, living room wall, kitchen floor, and kitchen counter. Upon exposure to ozone for 3 h, formaldehyde and C3-C10 saturated aldehydes, especially nonanal, were emitted as products of ozone-surface reactions. Carpet in newer homes had higher SERs than carpet in older homes. For example, the nonanal SER from the living room carpet was 80 microg m(-2) h(-1) in a 1 year old home, but only 8-20 microg m(-2) h(-1) in two homes that were greater than 10 years old. All kitchen countertops were very reactive and high SERs were observed, especially for nonanal. Product yields from countertops were consistent with the products of ozone reactions with oleic and linoleic esters, common in cooking oils. These findings suggest that carpet surfaces become depleted of reactants as they become oxidized over time. However, countertop surfaces, which are cleaned frequently or become covered in cooking oils, are continuously replenished with reactants. Over time, countertops may become the dominant contributor to indoor concentrations of secondary aldehydes. However, when total surface area is taken into account for the homes assessed, carpet is predicted to be the primary source of secondary emissions, even for older homes.
Article
Ozone-induced formation of aldehydes was studied on the surface and in the gas phase above carpets and on carpet components. Samples of four carpets were exposed to 100 ppb ozone. Emission rates of aldehydes and other organic compounds were measured from exposed and unexposed samples. Surface interactions of ozone with carpets produced C1-C13 n-aldehydes and several unsaturated aldehydes. Total aldehyde emission rates increased markedly with ozone exposure, from 1 to 70 microg m(-2) h(-1) for unexposed samples, to 60-800 microg m(-2) h(-1) during exposure. One exposed sample emitted large amounts of 2-nonenal (180-230 microg m(-2) h(-1)), a compound with a low odor threshold. Material balance modeling of a residence with this high emitting carpet suggests (1) that the concentration of 2-nonenal would be well above its odor threshold even in areas with only moderate ambient ozone levels and (2) that odorous levels of 2-nonenal could persist for years. Reactions of ozone with gas-phase primary emissions from carpet significantly reduced the levels of 4-phenylcyclohexene and produced small amounts of branched ketones. Separately measured patterns of aldehyde emissions from ozone exposure of linseed and tung oils were similar but not identical to those observed from ozone-exposed carpets.
Article
Cited By (since 1996): 195 , Export Date: 4 February 2013 , Source: Scopus , The following values have no corresponding Zotero field: Author Address: Dept. of Civ. and Environ. Eng., University of California, Berkeley, CA 94720-1710, United States Author Address: Environ. and Occup. Hlth. Sci. Inst., Univ. Med. and Dent. of New Jersey, Rutgers University, Piscataway, NJ 08854, United States Author Address: Intl. Ctr. Indoor Environ. and Ener., Technical University of Denmark, DK-2800 Lyngby, Denmark
Article
Ozone can react with surfaces, reducing indoor concentrations. Carpets may be important ozone sinks because of their high surface area. We conducted laboratory experiments to measure ozone uptake on four samples of whole carpet and on the corresponding carpet fibers and carpet backing. Results were parametrized in terms of reaction probability, defined as the rate of ozone loss on a surface normalized by the rate of ozone-surface collisions. For whole carpet and carpet-backing samples, we found the apparent reaction probability to be of magnitude 10-5 to 10-4. These results are referenced to the floor area that would be covered by the carpet, rather than to the total surface area of the carpet and its fibers. Reaction probabilities of the order of 10-7 to 10-6 were measured on carpet fibers, referenced to total estimated fiber area. The results indicate that carpet is of comparable significance to painted walls in scavenging ozone from indoor air. All samples tested exhibited aging, such that the rate of ozone uptake diminished with increasing cumulative exposure. Although reactions on carpeting can reduce human exposure to ozone, we caution that the reaction products may include volatile carbonyls that have low odor or irritation thresholds.
Article
This paper reports effects of reactions between ozone and selected terpenes on the concentrations and size distributions of airborne particles in a typical indoor setting. The studies were conducted in adjacent, identical offices. In the first set of experiments, known concentrations of ozone and a selected terpene (either d-limonene, alpha-terpinene, or a terpene-based cleaner whose major constituent is alpha-pinene) were deliberately introduced into one of the offices while the other office served as a control. Subsequent particle formation and redistribution were monitored with an eight-channel optical particle counter. Particle formation was observed in each terpene system, but was greatest in the case of d-limonene. The number of particles in the 0.1-0.2 mu m diameter size range was as much as 20 times larger in the office with deliberately supplemented ozone and d-limonene than in the office serving as the control. The concentration differences in the larger size ranges developed with time, indicating the importance of coagulation and condensation processes in this indoor environment. In the second set of experiments, d-limonene was deliberately introduced into one of the offices. but ozone was not supplemented in either office; instead, the indoor ozone concentrations were those that happened to be present (primarily as a consequence of outdoor-to-indoor transport). In the office that contained supplemental d-limonene, the concentrations of the 0.1-0.2 mu m particles tracked those of indoor ozone (the limiting reagent) and were as much as 10 times greater than levels measured in the comparable office that did not contain supplemental d-limonene. The results demonstrate that ozone/terpene reactions can be a significant source of sub-micron particles in indoor settings, and further illustrate the potential for reactions among commonly occurring indoor pollutants to markedly influence indoor environments.
Article
This study examines the influence of ventilation on chemical reactions among indoor pollutants. We have used a one compartment mass balance model to simulate unimolecular and bimolecular reactions occurring indoors. The initial modeling assumes steady-state conditions. However, at low air exchange rates, there may be insufficient time to achieve steady-state. Hence we have also modeled non steady-state scenarios. In the cases examined, the results demonstrate that the concentrations of products generated from reactions among indoor pollutants increase as the ventilation rate decreases. This is true for unimolecular and bimolecular reactions, regardless of whether the pollutants have indoor or outdoor sources. It is also true even when one of the pollutants has an outdoor concentration that displays large diurnal variations. We have supplemented the modeling studies with a series of experiments conducted in typical commercial offices. The reaction examined was that between ozone and limonene. The ozone was present as a consequence of outdoor-to-indoor transport while the limonene originated indoors. Results were obtained for low and high ventilation rates. Consistent with the modeling studies, the concentrations of monitored products were much larger at the lower ventilation rates (even though the ozone concentrations were lower). The potential for reactions among indoor pollutants to generate reactive and irritating products is an additional reason to maintain adequate ventilation in indoor environments.
Article
Transitory concentrations of ozone, within buildings located in photochemically smoggy areas, were found to lag in time nd to be only a little less in value as compared to corresponding outdoor concentrations. The ozone decomposition within buildings involved a heterogeneous mechanism. Experiments indicated that certain filters, especially activated charcoal, can be used to reduce indoor levels of ozone below the maximum acceptable limits.
Article
Consumer products can emit significant quantities of terpenes, which can react with ozone (03). Resulting byproducts include compounds with low vapor pressures that contribute to the growth of secondary organic aerosols (SOAs). The focus of this study was to evaluate the potential for SOA growth, in the presence of O3, following the use of a lime-scented liquid air freshener, a pine-scented solid air, freshener, a lemon-scented general-purpose cleaner, a wood floor cleaner, and a perfume. Two chamber experiments were performed for each of these five terpene-containing agents, one at an elevated O3 concentration and the other at a lower O3 concentration. Particle number and mass concentrations increased and O 3 concentrations decreased during each experiment. Experiments with terpene-based air fresheners produced the highest increases in particle number and mass concentrations. The results of this study clearly demonstrate that homogeneous reactions between O3 and terpenes from various consumer products can lead to increases in fine particle mass concentrations when these products are used indoors. Particle increases can occur during periods of elevated outdoor O3 concentrations or indoor O3 generation, coupled with elevated terpene releases. Human exposure to fine particles can be reduced by minimizing indoor terpene concentrations or O 3 concentrations.
Article
Cited By (since 1996): 28 , Export Date: 4 February 2013 , Source: Scopus , The following values have no corresponding Zotero field: Author Address: UMDNJ-RW Johnson Medical School, Rutgers University, Environ./Occup. Hlth. Sci. Institute, Piscataway, NJ 08854, United States Author Address: Intl. Ctr. for Indoor Environ./Ener., Technical University of Denmark, Lyngby DK, Denmark Author Address: Telcordia Technology, Red Bank, NJ, United States
Article
Cited By (since 1996): 33 , Export Date: 4 February 2013 , Source: Scopus , The following values have no corresponding Zotero field: Author Address: Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, United States Author Address: Indoor Environment Department, Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States Author Address: Department of Civil and Environmental Engineering, Arizona State University, Tempe, AZ 85287, United States
Article
Portable air cleaners can both remove and generate pollutants indoors. To investigate these phenomena, we conducted a two-phase investigation in a 14.75 m3 stainless steel chamber. In the first phase, particle size-resolved (12.6–514 nm diameter) clean air delivery rates (CADR) and efficiencies were determined, as were ozone emission rates, for two high-efficiency particle arresting (HEPA) filters, one electrostatic precipitator with a fan, and two ion generators without fans. The two HEPA air cleaners had count average CADR (standard deviation) of 188 (30) and 324 (44) m3 h−1; the electrostatic precipitator 284 (62) m3 h−1; and the two ion generators 41 (11) and 35 (13) m3 h−1. The electrostatic precipitator emitted ozone at a rate of 3.8±0.2 mg h−1, and the two ion generators 3.3±0.2 and 4.3±0.2 mg h−1. Ozone initiates reactions with certain unsaturated organic compounds that produce ultrafine and fine particles, carbonyls, other oxidized products, and free radicals. During the second phase, five different ion generators were operated separately in the presence of a plug-in liquid or solid air freshener, representing a strong terpene source. For air exchange rates of between 0.49 and 0.96 h−1, three ion generators acted as steady-state net particle generators in the entire measured range of 4.61–157 nm, and two generated particles in the range of approximately 10 to 39–55 nm. Terpene and aldehyde concentrations were also sampled for one ion generator, and concentrations of terpenes decreased and formaldehyde increased. Given these results, the pollutant removal benefits of ozone-generating air cleaners may be outweighed by the generation of indoor pollution.
Article
Cited By (since 1996): 96 , Export Date: 4 February 2013 , Source: Scopus , The following values have no corresponding Zotero field: Author Address: Environmental and Occupational Health Sciences Institute, University of Medicine and Dentistry of New Jersey, Rutgers University, 170 Frelinghuysen Rd., Piscataway, NJ 08854, United States Author Address: International Centre for Indoor Environment and Energy, Technical University of Denmark, Lyngby, Denmark
Article
Ionization-based air cleaners can emit high concentrations of ozone. With the aim to limit the ozone concentration below the standard value in actual use conditions, we propose a standard procedure for testing and ranking the ozone emission of air cleaners. It is demonstrated by testing 27 samples of air cleaners that ozone emission rate can be measured in an airtight environmental chamber, by applying a generation-decay model to the concentration increase curve. The results indicate that deposition velocities vd on chamber wall surfaces need to be better characterized so that the ozone emission of a tested product could be characterized by a three-parameter model. The model takes into account actual room sizes and surface material deposition effects to predict ozone concentrations in indoor applications. This procedure accounts for ozone decay effect in an explicit manner and allows using alternative testing chamber sizes other than as specified in the current Underwriters Laboratory standard.
Article
The effect of water on the initial secondary organic aerosol (SOA) formation from gas-phase ozonolysis of limonene, Delta(3)-carene, and a-pinene (similar to 3 and similar to 1.5 x 10(11) molecule cm(-3) reacted) has been investigated in a flow reactor at controlled relative humidity (RH), temperature (298 +/- 0.4 K), and reaction time (270 +/- 2 s). Low amounts of terpene converted minimize the impact of secondary reactions. A comparison of the SOA formation from the three terpenes was made for initial rate of reactions being around 7.5 x 10(8) and 15 x 10(8) molecule cm-3 s(-1). The most efficient species in producing SOA was limonene, while alpha-pinene was the least efficient. The results showed that an enhancement in water vapor concentration (< 2-85% RH) caused an increase in both integrated mass (M10-300nm) and total number (N10-300nm). The effect on number and mass were a factor of 2-3 and 4-8, respectively. Physical water up-take can partly explain the increase in mass, but not the observed increase in number. Therefore it was concluded that the increase in water concentration must, by a gas-phase reaction, produce more low volatility product(s).
Article
An indoor air quality model was used to predict dynamic particle mass concentrations based on homogeneous chemical mechanisms and partitioning of semi-volatile products to particles. The ozone–limonene reaction mechanism was combined with gas-phase chemistry of common atmospheric organic and inorganic compounds and incorporated into the indoor air quality model. Experiments were conducted in an environmental chamber to investigate secondary particle formation resulting from ozone/limonene reactions. Experimental results indicate that significant fine particle growth occurs due to the interaction of ozone and limonene and subsequent intermediate by-products. Secondary particle mass concentrations were estimated from the measured particle size distribution. Predicted particle mass concentrations were in good agreement with experimental results—generally within ∼25% at steady-state conditions. Both experimental and predicted results suggest that air exchange rate plays a significant role in determining secondary fine particle levels in indoor environments. Secondary particle mass concentrations are predicted to increase substantially with lower air exchange rates, an interesting result given a continuing trend toward more energy efficient buildings. Lower air exchange rates also shifted the particle size distribution toward larger particle diameters. Secondary particle mass concentrations are also predicted to increase with higher outdoor ozone concentrations, higher outdoor particle concentrations, higher indoor limonene emission rates, and lower indoor temperatures.
Article
A methodology has been established to quantify the ozone emission rate from electronic air cleaners, as well as the ozone decay parameter. Three different portable ionisation-type air cleaners were used in the experiments. A stainless steel environmental chamber with volume size 6.4m3 (1.6×2×2m) was employed in the study. The leakage rate of the chamber was measured to be 0.0042h-1 by a tracer decay gas test. The ozone growth curve within the chamber was used to quantify the ozone emission rate of the air cleaner and the ozone decay parameter. The emission rate and the decay parameter were determined by the initial slope and the equilibrium state of the growth curve simultaneously, and the technique of least squares fitting was introduced in the data analysis. The ozone emission rates and the decay parameters of Air Cleaner I, II, and III were found to be 119.4±15.6, 77.6±5.4, and 1092.3±112.5ppbh−1 and 2.59×10−1±0.03, 1.68×10−2± 0.001 and 9.48×10−2±0.01h−1, respectively. The wide range of the emission rates was believed to relate to the individual designs of the air cleaners. The variation in decay parameters obtained from the measurements was tentatively associated with the level of VOCs in the sampling environment.
Article
This Compendium was prepared to provide regional, state, and local environmental regulatory agencies, as well as other interested parties, with specific guidance on the determination of selected toxic organic compounds in ambient air. The decision was made to begin preparation of a Compendium that would provide specific sampling and analysis procedures, in a standardized format, for selected toxic organic compounds. The current Compendium consists of fourteen procedures considered to be of primary importance in current toxic organic monitoring efforts.
Article
As a result of new aerosol compositional information, we have implemented an exploratory model for predicting aerosol yields from the reaction of α-pinene with ozone in the atmosphere. This new approach has the ability to embrace a range of different atmospheric chemical conditions, which bring about biogenic aerosol formation. A kinetic mechanism was used to describe the gas-phase reactions of α-pinene with ozone. This reaction scheme produces low vapor pressure reaction products that distribute between gas and particle phases. Some of the products have subcooled liquid vapor pressures which are low enough to initiate self-nucleation. More volatile products such as pinonic acid and pinonaldehyde will not self-nucleate but will partition onto existing particle surfaces. Partitioning was treated as an equilibrium between the rate of particle uptake and rate of particle loss of semivolatile terpene reaction products. Given estimated liquid vapor pressures and activation energies of desorption, it was possible to calculate gas-particle equilibrium constants and aerosol desorption rate constants at different temperatures. This permitted an estimate of the rate of absorption from the gas phase. Gas- and aerosol-phase reactions were linked together in one chemical mechanism, and a chemical kinetics solver was used to predict reactant and product concentrations over time. Aerosol formation from the model was then compared with aerosol production observed from outdoor chamber experiments. Approximately 20−40% of the reacted α-pinene carbon appeared in the aerosol phase. Models vs experimental aerosol yields are shown in Figure 2 and illustrate that reasonable predictions of secondary aerosol formation are possible. The majority of the aerosol mass came from the mass transfer of gas-phase products to the aerosol phase. An important observation from the product data and the model was that as temperatures and aerosol mass changed from experiment to experiment, the composition of the aerosol changed.
Article
Several gas-phase carbonyl products of two terpenes, beta-pinene and D-limonene, and of the sesquiterpene, trans-caryophyllene, have been identified and their concentrations measured in experiments involving the reaction of these unsaturated biogenic hydrocarbons with ozone in the dark. Cyclohexane was added as a scavenger for the hydroxyl radical to minimize interferences from OH, which forms as a product of the ozone-hydrocarbon reaction. Carbonyl products were formaldehyde (yield = 0.42) and nopinone (yield = 0.22) from beta-pinene, formaldehyde (yield = 0.10) and 4-acetyl-1-methylcyclohexene from D-limonene, and formaldehyde (yield 0.08) from trans-caryophyllene. The nature and yields of these products are discussed in terms of the ozone-olefin reaction mechanism. The ozone-beta-pinene reaction rate constant, measured in the presence of cyclohexane, is 12.2 +/- 1.3 x 10(-18) cm3 molecule-1 s-1 at 22 +/- 1-degrees-C. Carbonyl products have also been identified in exploratory experiments with trans-caryophyllene and NO in sunlight.
Article
Formation of ultrafine particles, d p o100 nm, from gas-phase reaction of limonene with O 3 was studied. The concentration of reactants was chosen as close to realistic indoor conditions as possible. Two reaction chambers (1 and 14 m 3) were used. Particle number concentrations were measured using a CPC and size distributions by using a scanning mobility particle sizer (SMPS) system. Rapid formation of new particles was observed at low concentrations of reactants and close to zero ventilation rates. The maximum number of particles was correlated with the initial rate of formation of reaction products. An excess of O 3 tends to give higher maximum particle concentrations. Modeling work lead to the conclusion that significant nucleation starts when the mixing ratio of ''product'' from the reaction Limonene+O 3 -product ox exceeds 0.5–1 ppb. The secondary particles formed by atmospheric chemistry in indoor air contribute to the total particulate matter indoors and should be considered in terms of low-dose long-term exposure.
Article
A comprehensive indoor particle characterization study was conducted in nine Boston-area homes in 1998 in order to characterize sources of PM in indoor environments. State-of-the-art sampling methodologies were used to obtain continuous PM2.5 concentration and size distribution particulate data for both indoor and outdoor air. Study homes, five of which were sampled during two seasons, were monitored over week-long periods. Among other data collected during the extensive monitoring efforts were 24-hr elemental/organic carbon (EC/OC) particulate data as well as semi-continuous air exchange rates and time-activity information. This rich data set shows that indoor particle events tend to be brief, intermittent, and highly variable, thus requiring the use of continuous instrumentation for their characterization. In addition to dramatically increasing indoor PM2.5 concentrations, these data demonstrate that indoor particle events can significantly alter the size distribution and composition of indoor particles. Source event data demonstrate that the impacts of indoor activities are especially pronounced in the ultrafine (d(a) ≤ 0.1 μm) and coarse (2.5 ≤ d(a) ≤ 10 μm) modes. Among the sources of ultrafine particles characterized in this study are indoor ozone/terpene reactions. Furthermore, EC/OC data suggest that organic carbon is a major constituent of particles emitted during indoor source events. Whether exposures to indoor-generated particles, particularly from large short-term peak events, may be associated with adverse health effects will become clearer when biological mechanisms are better known.
Article
This study investigated the formation of secondary pollutants resulting from household product use in the presence of ozone. Experiments were conducted in a 50-m3 chamber simulating a residential room. The chamber was operated at conditions relevant to US residences in polluted areas during warm-weather seasons: an air exchange rate of 1.0 h−1 and an inlet ozone concentration of approximately 120 ppb, when included. Three products were used in separate experiments. An orange oil-based degreaser and a pine oil-based general-purpose cleaner were used for surface cleaning applications. A plug-in scented-oil air freshener (AFR) was operated for several days. Cleaning products were applied realistically with quantities scaled to simulate residential use rates. Concentrations of organic gases and secondary organic aerosol from the terpene-containing consumer products were measured with and without ozone introduction. In the absence of reactive chemicals, the chamber ozone level was approximately 60 ppb. Ozone was substantially consumed following cleaning product use, mainly by homogeneous reaction. For the AFR, ozone consumption was weaker and heterogeneous reaction with sorbed AFR-constituent VOCs was of similar magnitude to homogeneous reaction with continuously emitted constituents. Formaldehyde generation resulted from product use with ozone present, increasing indoor levels by the order of 10 ppb. Cleaning product use in the presence of ozone generated substantial fine particle concentrations (more than 100 μg m−3) in some experiments. Ozone consumption and elevated hydroxyl radical concentrations persisted for 10–12 h following brief cleaning events, indicating that secondary pollutant production can persist for extended periods.
Article
Numerous investigators have documented increases in the concentrations of airborne particles as a consequence of ozone/terpene reactions in indoor environments. This study examines the effect of building recirculation rates on the concentrations of secondary organic aerosol (SOA) resulting from reactions between indoor limonene and ozone. The experiments were conducted in a large environmental chamber using four recirculation rates (11, 14, 19 and 24 air change per hour (ACH)) and a constant outdoor air exchange rate (1 ACH) as well as constant emission rates for limonene and ozone. As the recirculation rates increased, the deposition velocities of ozone and SOA increased. As a consequence of reduced production rates (due to less ozone) and larger surface removal rates, number and mass concentrations of SOA in different size ranges decreased significantly at higher recirculation rates. Enhanced coagulation at higher recirculation rates also reduced particle number concentrations, while shifting size-distributions towards larger particles. The results have health implications beyond changes in exposures, since particle size is a factor that determines where a particle deposits in the respiratory tract.
Article
Building occupants, including cleaning personnel, are exposed to a wide variety of airborne chemicals when cleaning agents and air fresheners are used in buildings. Certain of these chemicals are listed by the state of California as toxic air contaminants (TACs) and a subset of these are regulated by the US federal government as hazardous air pollutants (HAPs). California's Proposition 65 list of species recognized as carcinogens or reproductive toxicants also includes constituents of certain cleaning products and air fresheners. In addition, many cleaning agents and air fresheners contain chemicals that can react with other air contaminants to yield potentially harmful secondary products. For example, terpenes can react rapidly with ozone in indoor air generating many secondary pollutants, including TACs such as formaldehyde. Furthermore, ozone–terpene reactions produce the hydroxyl radical, which reacts rapidly with organics, leading to the formation of other potentially toxic air pollutants. Indoor reactive chemistry involving the nitrate radical and cleaning-product constituents is also of concern, since it produces organic nitrates as well as some of the same oxidation products generated by ozone and hydroxyl radicals.
Article
Eleven portable air cleaning devices have been evaluated for control of indoor concentrations of respirable particles using in situ chamber decay tests. Following injection of cigarette smoke in a room-size chamber, decay rates for particle concentrations were obtained for total number concentration and for number concentration by particle size with and without air cleaner operation. The size distribution of the tobacco smoke particles was log normal with a count median diameter of 0.15 μm and a geometric standard deviation of 2.0. Without air cleaner operation, the natural mass-averaged surface deposition rate of particles was observed to be 0.1 h−1. Air cleaning rates for particles were found to be negligible for several small panel-filter devices, a residential-sized ion-generator, and a pair of mixing fans. Electrostatic precipitators and extended surface filters removed particles at substantial rates, and a HEPA-type filter was most efficient air cleaner studied.
Article
This study examined the impact of recirculation rates (7 and 14 h−1), ventilation rates (1 and 2 h−1), and filtration on secondary organic aerosols (SOAs) generated by ozone of outdoor origin reacting with limonene of indoor origin. Experiments were conducted within a recirculating air handling system that serviced an unoccupied, 236 m3 environmental chamber configured to simulate an office; either no filter, a new filter or a used filter was located downstream of where outdoor air mixed with return air. For otherwise comparable conditions, the SOA number and mass concentrations at a recirculation rate of 14 h−1 were significantly smaller than at a recirculation rate of 7 h−1. This was due primarily to lower ozone concentrations, resulting from increased surface removal, at the higher recirculation rate. Increased ventilation increased outdoor-to-indoor transport of ozone, but this was more than offset by the increased dilution of SOA derived from ozone-initiated chemistry. The presence of a particle filter (new or used) strikingly lowered SOA number and mass concentrations compared with conditions when no filter was present. Even though the particle filter in this study had only 35% single-pass removal efficiency for 100 nm particles, filtration efficiency was greatly amplified by recirculation. SOA particle levels were reduced to an even greater extent when an activated carbon filter was in the system, due to ozone removal by the carbon filter. These findings improve our understanding of the influence of commonly employed energy saving procedures on occupant exposures to ozone and ozone-derived SOA.
Article
Ozone concentrations were measured concurrently inside a simulated aircraft cabin and in the airstream providing ventilation air to the cabin. Ozone decay rates were also measured after cessation of ozone injection into the supply airstream. By systematically varying the presence or absence of people, soiled T-shirts, aircraft seats and a used HEPA filter, we have been able in the course of 24 experiments to isolate the contributions of these and other factors to the removal of ozone from the cabin air. In the case of this simulated aircraft, people were responsible for almost 60% of the ozone removal occurring within the cabin and recirculation system; respiration can only have been responsible for about 4% of this removal. The aircraft seats removed about 25% of the ozone; the loaded HEPA filter, 7%; and the other surfaces, 10%. A T-shirt that had been slept in overnight removed roughly 70% as much ozone as a person, indicating the importance of skin oils in ozone removal. The presence of the used HEPA filter in the recirculated airstream reduced the perceived air quality. Over a 5-h period, the overall ozone removal rate by cabin surfaces decreased at ∼3% h−1. With people present, the measured ratio of ozone's concentration in the cabin versus that outside the cabin was 0.15–0.21, smaller than levels reported in the literature. The results reinforce the conclusion that the optimal way to reduce people's exposure to both ozone and ozone oxidation products is to efficiently remove ozone from the air supply system of an aircraft.
Article
Some domestic ionization-type air cleaners incorporate or solely rely on corona effect to electrically charge particulates so that surface deposition velocities of dusts are accelerated in indoor environment. On the other hand, ozone, as an indoor air pollutant, is generated as a by-product. Two standard test procedures exist, respectively quantifying the dust removal capacity and ozone emission. However, these standards fail to adequately specify the chamber surface decay effect with regard to ozone and particulates, which will add uncertainty to the test results. In this paper, we will present our testing results on 27 commercially available products in Hong Kong to illustrate the significance of chamber surface deposition effects. The results will be useful for the manufacturers to quantify the performances of their product design.
Article
The rate of deposition of reactive gaseous pollutants onto indoor surfaces is examined, taking into account mass transport processes and the kinetics of gas-surface interactions. A conceptual model for predicting indoor deposition velocities is proposed, and approximate analysis based on this model is used to obtain algebraic expressions for the deposition velocity of reactive gases under three model airflow conditions: (1) forced laminar convection parallel to a flat plate, (2) laminar natural convection flow along an isothermal vertical plate, and (3) homogeneous turbulence in an enclosure. Numerical simulations are used to refine the approximate analysis results and to predict reactive gas deposition under laminar natural convection flow in an enclosure. The kinetics of gas-surface interactions are modeled in terms of the reaction probability γ, defined as the fraction of pollutant molecular collisions with a surface that result in irreversible removal. Values of γ for the reaction of ozone with surfaces are obtained from published reaction chamber and tube penetration experiments. For common indoor materials, values range from as low as O(10−7) for glass and aluminium to O(10−5–10−4) for materials such as bricks, concrete and latex paint. Our results indicate that ozone deposition occurs at the transport-limited rate when γ > − 3 × 10−4 for typical indoor air flow conditions, and that ozone deposition can be predicted by surface kinetics alone if γ < ∼ 5 × 10−7.
Article
The “personal cloud” effect and its impact on human exposure to airborne pollutants are well documented. A great deal is also known regarding indoor air chemistry, particularly as related to ozone reactions with mono-terpenes. In this paper we hypothesize the presence of personal reactive clouds that result from ozone reactions with terpenes and terpenoids emitted from personal care products. A proof of concept assessment was completed based on reaction rates between ozone and five reactive organic compounds that are found in personal care products. Screening experiments were also completed with three perfumes and two hairsprays to determine the extent of secondary organic aerosol formation in the breathing zone of a subject who had applied these products. The results of screening calculations and preliminary experiments confirm that chemistry occurs in the near-head region of individuals who apply scented personal care products to their hair or facial skin. Additional research is needed to characterize reaction products and health consequences associated with near-head chemistry and associated personal reactive clouds.
Article
Experiments were conducted in an 11 m3 environmental chamber to investigate secondary particles resulting from homogeneous reactions between ozone and α-pinene. Experimental results indicate that rapid fine particle growth occurs due to homogeneous reactions between ozone and α-pinene, and subsequent gas-to-particle partitioning of the products. A new indoor air quality model was used to predict dynamic particle mass concentrations based on detailed homogeneous chemical mechanisms and partitioning of semi-volatile products to particles. Chamber particle mass concentrations were estimated from measured particle size distributions and were in reasonable agreement with results predicted from the model. Both experimental and model results indicate that secondary particle mass concentrations increase substantially with lower air exchange rates. This is an interesting result, given a continuing trend toward more energy-efficient buildings. Secondary particle mass concentrations are also predicted to increase with lower indoor temperatures, higher outdoor ozone concentrations, higher outdoor particle concentrations, and higher indoor α-pinene emissions rates.
Article
The heterogeneous chemistry of ozone on interior latex paint was investigated in a tube flow reactor. The emissions of several polar volatile organic compounds (VOCs) including organic acids and carbonyls (aldehydes and ketones) were measured while a glass tube coated with latex paint was exposed to clean air and ozone, Four different commercial brands of latex paint were tested. Formic and acetic acids were not found to be generated via ozone reactions; however, both were found to off-gas from the latex paints, and the off-gasing increased with increasing relative humidity. The off-gasing rates are large enough, particularly for acetic acid, to impact residential. concentrations significantly. Formaldehyde was found to be produced by reactions related to the ozone concentration. There was some evidence that acetaldehyde and acetone may also be produced by processes related to the ozone concentration. A steady-state model is presented that is used to extrapolate the chamber results to a representative indoor environment. The model is based on an experimentally derived parameter termed the VOC formation factor, which is defined as the number of VOC molecules of a particular species formed via an ozone reaction divided by the total number of ozone molecules sticking to the surface. Using this model, it was found that formaldehyde production via ozone reactions is significant enough to impact indoor concentrations of formaldehyde.
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In urban and suburban settings, indoor ozone exposures can represent a significant fraction of an individual's total exposure. The decay rate, one of the factors determining indoor ozone concentrations, is inadequately understood in residences. Decay rates were calculated by introducing outdoor air containing 80-160 parts per billion ozone into 43 residences and monitoring the reduction in indoor concentration as a function of time. The mean decay rate measured in the living rooms of 43 Southern California homes was 2.80 +/- 1.30 hr-1, with an average ozone deposition velocity of 0.049 +/- 0.017 cm/sec. The experimental protocol was evaluated for precision by repeating measurements in one residence on five different days, collecting 44 same-day replicate measurements, and by simultaneous measurements at two locations in six homes. Measured decay rates were significantly correlated with house type and the number of bedrooms. The observed decay rates were higher in multiple-family homes and homes with fewer than three bedrooms. Homes with higher surface-area-to-volume ratios had higher decay rates. The ratio of indoor-to-outdoor ozone concentrations in homes not using air conditioning and open windows was 68 +/- 18%, while the ratio of indoor-to-outdoor ozone was less than 10% for the homes with air conditioning in use.
Article
Unlabelled: Limonene ozonolysis was examined under conditions relevant to indoor environments in terms of temperatures, air exchange rates, and reagent concentrations. Secondary organic aerosols (SOA) produced and particle-bound reactive oxygen species (ROS) were studied under situations when the product of the two reagent concentrations was constant, the specific concentration combinations play an important role in determining the total SOA formed. A combination of concentration ratios of ozone/limonene between 1 and 2 produce the maximum SOA concentration. The two enantiomers, R-(+)-limonene and S-(-)-limonene, were found to have similar SOA yields. The measured ROS concentrations for limonene and ozone concentrations relevant to prevailing indoor concentrations ranged from 5.2 to 14.5 nmol/m(3) equivalent of H2O2. It was found that particle samples aged for 24 h in freezer lost a discernible fraction of the ROS compared to fresh samples. The residual ROS concentrations were around 83-97% of the values obtained from the analysis of samples immediately after collection. The ROS formed from limonene ozonolysis could be separated into three categories as short-lived, high reactive, and volatile; semi-volatile and relatively stable; non-volatile and low-reactive species based on ROS measurements under various conditions. Such chemical and physical characterization of the ROS in terms of reactivity and volatility provides useful insights into nature of ROS. Practical implications: A better understanding of the formation mechanism of secondary organic aerosol generated from indoor chemistry allows us to evaluate and predict the exposure under such environments. Measurements of particle-bound ROS shed light on potential adverse health effect associated with exposure to particles.
Article
Abstract Abstract The formation of secondary organic aerosol (SOA) produced from α-pinene ozonolysis was examined using a dynamic chamber system that allowed the simulation of ventilated indoor environments. Particle-bound reactive species (ROS) including peroxides, peroxy radicals and ions that could penetrate into the lungs and deliver oxidative stress to the tissue causing damage were quantitatively determined from filters collected from the chamber. ROS was determined using dichlorofluorescin such that resulting fluorescent intensities were converted to equivalent H2O2 concentrations. Measured ROS concentrations at α-pinene and ozone concentrations relevant to prevailing indoor concentrations ranged from 1.1 to 7.2 nmol/m3 of H2O2. Particle density was also determined from scanning mobility particle sizer measurements and mass collected onto filters to obtain volume and mass concentration, respectively. Partitioning theory reveals the fact that with increased SOA mass loading, even for more volatile species, partitioning onto particle phase is favored relative to low SOA mass loadings. Other recent studies have found changes in composition of the SOA depending on the precursor VOC concentrations. This behavior was reflected in these experiments in terms of a change of density. Measured densities ranged from 1.07 to 1.69 g/cm3.
Article
There are concerns about ozone-initiated chemistry, because the formation of gaseous oxidation products and ultrafine particles may increase complaints, morbidity and mortality. Here we address the question whether the gaseous products or the ultrafine particles from the ozone-initiated chemistry of limonene, a common and abundant indoor pollutant, cause acute airway effects. The effects on the airways by d-limonene, a ca. 16s old ozone/d-limonene mixture, and clean air were evaluated by a mice bioassay, from which sensory irritation of the upper airways, airflow limitation, and pulmonary irritation can be obtained. A denuder was inserted to separate the ultrafine particles from the gaseous products prior to the exposure chamber. Reduction of mean respiratory frequency (>30%) and 230% increase of time of brake were observed without denuder, during 30min exposure, to the ozonolyzed d-limonene mixture, which are indicative of prominent sensory effects. The initial concentrations (ppm) were 40 d-limonene and 4 ozone. The exposure concentrations (ppm) were about 35 d-limonene and 0.05 ozone. Formaldehyde and residual d-limonene, the salient sensory irritants, accounted for up to three-fourth of the sensory irritation.