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Correlation amongst Indoor Air Quality, Ventilation and Carbon Dioxide
N. L. Sireesha
Department of Architecture, School of Planning and Architecture, Jawaharlal Nehru Fine arts and
Architecture University, Hyderabad, Telangana, India
Received 12 January 2017, accepted in final revised form 2 April 2017
Abstract
The calculation of carbon dioxide (CO2) intensities can be employed to see the quality of
indoor air and ventilation. The studies undertaken till date have been distorted. The current
study summaries the association amongst carbon dioxide and building air quality and
ventilation, with carbon dioxide being the marker to evaluate air quality and ventilation
performance. High carbon dioxide intensities may show insufficient ventilation per
occupant and high indoor contaminants intensities, resulting in the Sick Building Syndrome
(SBI) Symptoms. The researcher assessed the literature related to indoor air quality (IAQ),
ventilation, and building-linked health issues in schools linked to CO2 discharges and
recognised general indicated building-linked well-being signs found in schools. A high rise
in the ventilation rate or enhancement in ventilation efficacy and/or indoor contaminant
source regulation would be anticipated to reduce the occurrence of chosen signs to its
optimum.
Keywords: Indoor air quality; Schools; Carbon dioxide; Ventilation; Health.
© 2017 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.
doi: http://dx.doi.org/10.3329/jsr.v9i2.31107 J. Sci. Res. 9 (2), 179-192 (2017)
1. Introduction
In the advanced world, over ninety percent of our lives rely on the quality of indoor air
found in our homes, at the places where we work and in vehicles. The technological
developments made in the developed countries have almost eradicated the influence of
climate on people; people have successfully developed artificial climates that permit them
to spend a long time indoors. Thanks to the artificial, automated climate control, people
can live at any location cross the globe; however we are exposed to the quality of indoor
air that we develop. Usually, the indoor air quality shares a direct association to the
outdoor air quality, which enhances as people shift closer to large amount of vegetation
and far away from the urban zones. The air is purified by the natural procedure of
photosynthesis in vegetation since carbon dioxide is used by plants that release oxygen in
the air.
Corresponding author: nlsireesha@gmail.com
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Indoor Air Quality, Ventilation and Carbon Dioxide
Sadly, it is not realistic to provide adequate indoor vegetation in all the buildings
especially to purify the indoor air sufficiently. Hence, the air we respire is frequently
discovered to be of inferior quality and/or dangerously polluted. Unseen to the human
eyes, these pollutants comprise of living and non-living objects including gases, fibres,
dust, and microbes. Also almost fifty percent of their waking hours are spent by children
in their schools. Thus, sustaining sufficient indoor air quality (IAQ) in schools is
becoming important for both facility managers and building operating engineers. A crucial
aspect for sustaining sufficient indoor air quality is outside air to reduce indoor air
contaminants and consume these pollutants in addition to the moisture and smells from
the buildings.
Over-exposure to the optimum outdoor contaminant levels as set by the National
Ambient Air Quality Standards, United States Environmental Protection Agency in the
year 1997, is a crucial issue for children and people of old age. Since children breathe a
higher air volume compared to adults in context to their body weight, the danger to the
children is higher in such settings. The body stress of the toxin contaminants is much
more for smaller children compared to the adults in settings that similar in character.
Compared to an adult’s breathing area, the number of contaminants present in a child’s
breathing area is much more. There is a great impact of the CO2 concentration over the
decision making and cognitive thinking of humans as disclosed from the new
investigations from Harvard School of Public Health. These effects are direct and negative
to the aforementioned activities. The research was performed on American citizens and
their children going to schools, offices, home, cars, planes, classrooms etc. The indoor
CO2 concentrations are inescapably higher than the outdoor air for ventilations. The main
reason behind this continuously increasing baseline of CO2 concentrations are the various
activities like burning of the fossil fuels performed by humans in their everyday life.
These activities have become essential and inevitable part of our lives. The results of this
research are significant for the climatic policies also giving a new impetus for public
health in order to control and maintain the global CO2 concentration level reduced [1].
The degree of CO2 in an air sample is commonly articulated to be as per million (ppm).
The outdoor air in majority of the places has around 380 parts per million (ppm) of carbon
dioxide. In areas with heavy vehicular traffic, areas where industries or located or places
wherein there are sources of combustion, the outdoor air contains a higher level of CO2
intensities. In areas where indoor intensities are higher (contrast to the external air), the
cause is attributed to the occupants in the building. Individuals breathe out carbon
dioxide—the mean adult’s breath has around 35,000 to 50,000 ppm of CO2 (100 times
higher than outdoor air). In the absence of sufficient ventilation to reduce and eliminate
the CO2 that is consistently being thrown out by the occupants, CO2 can gather and its
intensity becomes stronger. The extant technology permits simple and comparatively
cheaper calculation of CO2 as a marker to facilitate that the ventilation systems (for high
density occupancy zones) are providing the suggested minimum quantities of outside air
to the building’s occupants.
N. L. Sireesha J. Sci. Res. 9(2), 179-192 (2017)
181
The intensities of CO2 found in most schools are much below the 5,000 ppm
occupational safety criteria (time weighted mean for an eight-hour workday in a 40 hr
work week) for an industrial place of work. While levels below 5,000 ppm are not
regarded to have any dangerous risks to the well-being, experience shows that individuals
in schools with higher CO2 intensities are likely to complain about drowsiness, tiredness
and an overall feeling of the air not being fresh.
1.1. General air contaminants present in schools
The majority part of children is spent in the school environment. There are various factors
which exhibit great impact on the indoor environmental quality of school. The factors are:
location or locality of school, the condition of the school building, its regular cleaning
(neat and tidy campus) and maintenance. Apart from these there are various pollutants
whose presence also influences and exhibits impacts on the indoor quality like presence of
bacteria, moulds etc. Whereas, the main air contaminants characteristic present in school
comprises of environmental tobacco smoke, formaldehyde, volatile organic compounds,
nitrogen oxides, carbon monoxide, carbon dioxide, allergens, pathogens, radon, pesticides,
lead, and dust [2,3]. Further, detailed descriptions are:
Environmental tobacco smoke (ETS) is the amalgamation of two kinds of smoke
from burning tobacco products: side stream smoke, (smoke that is emitted between
the puffs of a burning cigarette, pipe, or cigar), and conventional smoke (the smoke
that is respired by the smoker.)
Fig. 1. The indoor air contaminant sources, and their outcome in the building setting.
Source: School Indoor Air Quality. Best Management Practices Manual, November, 2003. [4].
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Indoor Air Quality, Ventilation and Carbon Dioxide
Sources such as particleboard, plywood, textiles, adhesives, foam insulation, and
pressed wood furniture, cabinets and shelving release formaldehyde.
Sources like generally-utilised cleaners, personal care products, adhesives, paints,
pesticides solvents, wood preservatives, furnishings, and copying machines discharge
explosive organic compounds.
The procedure of combustion, welding, and tobacco smoke releases nitrogen oxide.
The partial combustion or unvented gas, kerosene heaters, boilers, furnaces, auto,
truck, and bus exhaust releases carbon monoxide.
All the combustion procedures and human metabolic procedures release carbon
dioxide.
Humans, animals, the environment, draperies, carpet, dust collecting sources, cooling
towers, dirty cooling coils, humidifiers, condensate drains, and ductwork, which can
gestate bacteria and moulds release allergens and pathogens.
The earth around some buildings, well water, and even few masonry blocks release
radon.
Pesticides put close to the building can be pulled indoors, contaminating the indoor
environment.
The soil, fleecy surfaces, and pollen, burning wood, oil, or burning coal [5] releases dust.
2. Rates of Ventilation and CO2 Intensities in Schools
Schools have very rarely calculated the ventilation rates, despite insufficient ventilation
alleged to be a crucial criterion resulting in documented well-being signs [6] suggests at
least a ventilation rate of 8 L/s-person (15 cfm/person) for classrooms. Considering the
usual occupant density of 33 per 90 m2 (1000 ft2) and the ceiling height to be around 3m
(10 ft.), the present SHRAE criterion would need an air exchange rate of around 3 air
changes per hr (ACH) for a classroom. Three researches were conducted in schools that
did not comply with the above criterion. Some researches offered only the average data
while others have details for individual schools. Some data were for the same schools
under varied settings like before and after radon alleviation. A study by Turk et al. [7]
discussed ventilation calculations made in 6 schools that did not follow the norms located
in the U.S. Northwest-2 in Portland, OR and 4 in Spokane, WA. The age of the schools
varied from 3 years to 25 years with 1 to 3 stories. All the schools spoke about automatic
ventilation systems of some kind. Ventilation rates, gauged on the entire building volume
basis, varied from 4.5 L/s-person to 31 L/s-person. The entire or aggregate building rate,
on the other hand, comprises of places that are vacant including the hallways and
gymnasiums, and as indicated by the researchers, this aggregate rate miscalculates the
domestic ventilation rate of classes that are vacant. For instance, in one of the elementary
schools, the ventilation rate of the entire building was 4.5 L/s-person while in the
occupied classrooms, the ventilation rate was merely 1.6 L/s-person. Turk et al. [8] also
stated that ventilation rates calculated in 2 schools located in Sante Fe, NM, were being
alleviated for high radon intensities. Twelve before and after radon alleviation ventilation
N. L. Sireesha J. Sci. Res. 9(2), 179-192 (2017)
183
rates were reported to be less than 3 ACH with one school being the sole exclusion.
According to Nielsen [9], ventilation calculations were made in 11 randomly chosen
schools in Denmark. The calculations were taken in 2 classrooms for 3 sequential days.
The mean ventilation rate was discovered to be 6.4 L/s-person with a span of 1.8 - 15.4
L/s-person.
2.1. CO2 and SBS researches in the literature
A latest appraisal indicated that around fifty percent out of 22 researches related to the
Sick Building Syndrome (SBI) signs in office buildings indicated that enhanced indoor
CO2 intensities were affirmatively linked with a statistically crucial rise in the occurrence
of a single or more than a single SBS sign. SBS signs linked with CO2 comprised of
tiredness, headaches, issues with the eyes, nose, issues with the respiratory tract, and
entire sign scores. Seventy percent of researches of automatically ventilated and air
conditioned buildings discovered to have a crucial link amongst a rise in CO2 and SBS
signs. Building ventilation was also linked with SBS signs.
2.2. CO2 intensities
The intensities of CO2 are frequently employed as a substitute of the rate of outside supply
air per occupant. Indoor CO2 intensities that surpass around 1000 ppm are usually
considered to indicate that the ventilation rates are offensive in context to body smells.
Intensities of CO2 below 1000 ppm do not always ensure that the ventilation rate is
sufficient for eradication of air contaminants from other indoor sources [10]. It is tough to
sufficiently typify indoor CO2 intensities as they are calculated based on occupancy and
ventilation rate, both differing as a function of time. Grab samples or other short-run
calculations may be insufficient to offer details on the long-run ventilation settings in the
schools. There is a large unpredictability in the techniques employed to typify the indoor
CO2 intensities in the studies analysed subsequently. The mean and spans of CO2
intensities indicated in the scientific literature for U.S. and Canadian schools, and for
European schools, correspondingly, for both schools that meet or fail to meet the criterion
are indicated in Figs. 2 and 3 subsequently. In several of the reports, intensities are close
to or merely little higher than the ASHRAE criterion of 1,000 ppm, irrespective of
condition whether they are conforming or non-conforming. CO2 intensities that exceed
1000 ppm were also seen in few non-conforming schools. Brennan et al. [11] undertook
mid-afternoon CO2 calculations in a non-random research of 9 U.S. non-conforming
schools. Intensities differed from around 400 to 5,000 ppm (mean = 1480 ppm). CO2
intensities varied from around 400 to 5,000 ppm (mean = 1480 ppm). Ina round 74% of
the schools, the CO2 intensities surpassed the 1000 ppm ASHRAE ventilation criterion.
The aggregate the CO2 intensities for 3 non-conforming schools in Alberta, Canada were
less than 1000 ppm despite few calculations surpassing this intensities [12]. The aggregate
CO2 intensity in one portable classroom stood at 1950 ppm. The number of classrooms
analysed in all schools were not given. According to Turk, et al. (1993), little high CO2
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Indoor Air Quality, Ventilation and Carbon Dioxide
intensities for two schools in New Mexico before to and post the radon elimination. Fisher
et al., and Thorne [13] indicate comparable enhanced indoor CO2 intensities before radon
being eliminated, with lowering to levels less than 1000 ppm after the elimination of CO2
intensity calculations indicated for several of the mon-conforming European Schools were
almost equal to or more than 1000 ppm. According to Lasovic et al. [14], the researcher
tested the CO2 concentration level in two Schools, in the first School C the mean outdoor
CO2 concentration level was 424 ppm and 575 ppm in HS and NHS respectively. For the
second School D, the mean outdoor CO2 concentration level was 524 ppm and 608 ppm in
HS and NHS respectively. It was previously reported that 1000 ppm CO2 concentration in
the indoor environment in accordance with body odours are not accepted. Two Swedish
Schools [15] had a mean intensity of 1420 and 1850 ppm. Median CO2 intensities stood at
1070 ppm (range 800 to 1600 ppm) in a research of 10 Swedish non-conforming Schools,
and 1100 ppm (range 875 to 2150 ppm) in 11 schools with higher occurrence of SBS
signs [16]. Nielsen et al. discussed a measurement that indicated a CO2 range of around
500-1500 ppm (average = 1000 ppm) in 11 Danish schools. Several of the European
calculations used colorimetric indicator tubes over a small time span. Potting, et al. [17]
recounted an epidemiological research that included 339 students in 3 Dutch complaint
schools (14 classrooms) and 4 schools that had no teacher grievances (207 controls). All
these schools were built after 1980. During 27 to 97% of the school time, the CO2
intensity in all the classrooms surpassed the Dutch criterion of 1200 ppm. The levels in
one classroom was more than 2500 ppm CO2, 73% of the time while the level of CO2
stood at 1100 ppm in another room, when the school began during the day. Smedje et al.
[18,19] recounted the mean and ranges of indoor CO2 intensities for 96 classrooms in 38
Swedish schools that were chosen randomly from a populace of 130 schools; 61% of these
schools boasted of automatic supply and exhaust air systems while the rest had natural
ventilation. The intensities were aggregated to be around 990 ppm CO2 for 38 schools, but
surpassed 1000 ppm for 41% of the calculations (maximum = 2800 ppm).
Overall, CO2 calculations in schools recommend a crucial ratio of classrooms is likely
not to fulfil the ASHRAE Standard 62-1999 for minimum ventilation rate, at least
sometimes. Additionally, despite there being limited data it seems that this scenario may
be more severe in portable classrooms. This remark is endorsed by different ventilation
rate calculations. There is no validation to recommend that higher CO2 intensities were
limited to schools that have grievances. On the other hand, there have not been any
symbolic investigations of school classrooms to offer details on the circulations of CO2
intensities or ventilation rates in schools or across the state, regional or across the country
too. Intensities of different contaminants discharged by the occupants and building
materials and fittings will be more under these settings than if the ASHRAE ventilation
criterion were fulfilled. Special emphasis needs to be given to the possibility of enhanced
danger of catching specific infectious respiratory sicknesses, like the flu and common
colds in classrooms with reduced ventilation rates [20].
Carbon dioxide is not the sole challenging source of inferior air quality in school
buildings. Well-being issues between the students and teachers will lead to the increase of
N. L. Sireesha J. Sci. Res. 9(2), 179-192 (2017)
185
illnesses and leaves for falling sick, inferior student involvement and attainment. It is
remarkable to think that a gradual rise in carbon dioxide may result in such big issues for
both teachers and students in the school.
2.3. Causes for inferior indoor air quality
The main causes for inferior indoor air quality include insufficient ventilation, ineffective
filtration, and inferior hygiene of air handling units. These shortages are damaging to
providing superior indoor air quality, particularly in schools. The American Society of
Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) suggest the Standard
62-1999, Ventilation for Acceptable Indoor Air Quality [21] as mentioned subsequently in
table no.1.
Table 1. Acceptable Ventilation IAQ as given by ASHRAE
Application/Area
CFM* per person
* CFM cubic feet per minute
1
Classrooms
15
2
Music Rooms
15
3
Libraries
15
4
Auditoriums
15
5
Spectator Sport Areas
15
6
Playing Floors
20
7
Office Spaces
20
8
Conference Rooms
20
9
Cafeteria
20
10
Kitchen (Cooking)
20
11
Patient Rooms
20
2.4. Suggested criteria for satisfactory ventilations
There are different criteria and norms described by schools for the ventilation rates. The
American Society of Heating, Refrigeration, and Air Conditioning Engineers [9] Standard
62 is the most preferred criterion. There are some states and local codes that have
espoused the ASHRAE Standard 62 ventilation needs. As per ASHRAE Standard 62,
classrooms need to have 15 cubic feet per minute (cfm) outside air per person, and offices
need to be provided with 20 cfm outside air per person. ASHRAE has also provided
ventilation rates for other indoor locations. The rates may alter since the Standard 62 is
presently being modified. According to ASHRAE, indoor CO2 intensities need to be
sustained at or be below 1,000 ppm in schools (refer to the subsequent chart) employing
CO2 as a marker of ventilation. It is suggested by ASHRAE that indoor CO2 intensities
must not surpass the outdoor focus by over 600 ppm.
The association amongst CO2 levels and outside air ventilation rate can be seen by the
Table no:2, when outdoor CO2 is around 350 ppm [22].
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Indoor Air Quality, Ventilation and Carbon Dioxide
2.4.1. Ventilation and ensuing co2 intensities
Table 2. Association amongst CO2 levels and outside air ventilation rate.
Carbon dioxide
Outside air (cfm per person)
CO2 differential
(inside/outside)
800 ppm recommends around
20 cfm (or less)
500 ppm
1,000 ppm recommends around
15 cfm (or less)
650 ppm
1,400 ppm recommends around
10 cfm (or less)
1,050 ppm
2,400 ppm recommends around
5 cfm (or less)
2,050 ppm
Source: Rich Prill,"Why measure carbon dioxide inside the buildings" Washington State University
Extension Energy Program, 2000
Remark: The Table 2 provides an estimated value of CO2 and depends on a consistent
number of inactive adult occupants, a constant ventilation rate, an outdoor air CO2
intensity of about 380 ppm, and good mixing of the indoor air.
The levels of carbon dioxide in adequately ventilated buildings should be around 600
ppm and 1,000 ppm, with a floor or building mean of 800 ppm or less. If the mean carbon
dioxide levels within a building are sustained at less than 800 ppm, with rough
temperature and humidity levels, grievances related to indoor air quality would be
mitigated. If the carbon dioxide levels exceed than 1,000 ppm, people may raise
grievances.
Thus, 1,000 ppm needs to be employed as a directive for enhancing ventilation. If a
building surpasses the directive, it must not be inferred to be a dangerous or life-
intimidating scenario. A higher carbon dioxide level is merely a sign of insufficient
amount of external air being circulated inside the building. Carbon dioxide is a standard
element of respired breath and is generally calculated as an inspection mode to assess if
sufficient volumes of fresh outdoor air are being advanced into the indoor air. The outdoor
level of carbon dioxide generally ranges from 300 to 400 ppm. The level of carbon
dioxide level inside a building is usually higher compared to outside the building, even in
buildings that have limited grievances pertaining to quality of indoor air. If the indoor
carbon dioxide levels surpass 1,000 ppm, there is a chance of insufficient ventilation and
grievances including headaches, tiredness and eye and throat inflammation may become
common. One must note that carbon dioxide per sec cannot be held liable for these
grievances; a high level of carbon dioxide, on the other hand, may show that other
pollutants in the building also exist at high levels and may be accountable for the
grievances given by the occupants.
N. L. Sireesha J. Sci. Res. 9(2), 179-192 (2017)
187
Fig. 2. Carbon dioxide and its effects on Human body
Source: Indoor air quality in schools affects grades. By Sarah Croft[23]
The directives above are not useful in building zones where there are likely sources of
carbon dioxide beyond the respired breath. Other sources comprise of exhaust gas from
kilns, internal combustion engines, dry ice, etc. Under such settings, the Occupational
Safety and Health Administration (OSHA) criterion for carbon dioxide is applicable. The
OSHA criterion stands at an eight-hour time-weighted average (TWA) of 5,000 ppm with
a short-term 15-minute average limit of 30,000 ppm.
3. Present Technology and IAQ
Presently, the calculation of carbon dioxide is a crucial method to facilitate sufficient
outside air ventilation while at the same time, save energy by lowering the number of
over-ventilated buildings. Technological advancements have allowed people to employ
comparatively cheaper CO2 sensors to consistently keep a check on the levels of CO2 in a
building. These CO2 values can be utilised by the heating, ventilation and air-conditioning
(HVAC) control system to repeatedly regulate the volume of outside air to sustain indoor
CO2 at or below a pre-decided intended intensity. This policy is referred to as demand
controlled ventilation (DCV). DCV systems are particularly beneficial for those areas or
places that boast of variable occupancy rates: the ventilation rate reacts correspondingly to
modifications in the density of occupation [24]. The subsequent Table indicates (Table 3)
the well-being impacts that a result of the building up of CO2 in a setting and the
equivalent regulatory methods.
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Indoor Air Quality, Ventilation and Carbon Dioxide
A study undertaken by Scheff, Paulius, Huang and Conroy [25] related to indoor air
quality in middle school employed CO2 as a marker for efficient ventilation. The emphasis
of the research was on the association amongst occupancy and the gauged intensities of
carbon dioxide in addition to an assessment of the utilisation of carbon dioxide as a
marker for ventilation in the school. The school was typified to be one with no health
conditions, adequate maintenance schedules; carpets were absent both in the hallways and
the classrooms; further there was no major remodelling that was undertaken. The
sampling was conducted when the classes were on. The sample locations for different
environmental comfort and contaminant criteria included the cafeteria, a science
classroom, an art classroom, and the lobby outside the main office, and one outdoor space
consistently for seven days in February 1997. A constant link amongst hourly occupancy
and equivalent carbon dioxide intensities were observed. The intensities of carbon dioxide
in the cafeteria, art room, and lobby were found to be as per the directives of American
Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) for
comfort (< 1000 ppm). It was seen that highest intensities of carbon dioxide (often
surpassing 1000 ppm) existed in the science room mainly due to the high occupancy and
defunct unit ventilators. It was discovered that in the art room, cafeteria and the lobby, the
calculated ventilation rates fulfilled the criteria provided by ASHRAE. It was solely the
science room that failed to fulfil the ASHRAE criteria on one of the three days evaluated
as it depended purely on natural ventilation. Thus, the research indicated the benefit of
gathering indoor CO2 and occupancy data when researchers examined the indoor air
quality in schools.
Table 3. Well-being Impacts of CO2 in setting along with regulatory techniques.
Contaminant
Sources
Impact on Comfort and well-being
Regulatory
Techniques
Carbon
dioxide is a
gas that has
no color, odor
or taste. It is
the result of
carbon
combustion
process being
completed.
The sources of
carbon dioxide
include all
combustion
procedures.
Intensities of
CO2 from
individuals are
extant in
buildings that
are occupied.
Carbon dioxide is an ingenuous gas that
suffocates. At intensities that surpass
1.5%, it becomes difficult to inhale and
exhale. If the intensity surpasses 3% CO2
leads to one feeling nauseous, having
headaches and causes dizziness. If the
intensity of CO2 is around 6% to 8%, it
may lead to numbness and even death. At
reduced intensities (0.1 percent), people in
the building may suffer from headaches,
tiredness, eye or respiratory tract
inflammation. At reduced intensities, the
buildup of CO2 shows insufficient.
Aerate with
fresh air to
regulate the
levels of
carbon dioxide.
The rate of
ventilation
must fulfill the
WAC 51-13.
This needs 15
CFM/person in
a characteristic
classroom.
Source: School Indoor Air Quality. Best Management Practices Manual, November, 2003.
N. L. Sireesha J. Sci. Res. 9(2), 179-192 (2017)
189
3.1. Assessment of performance loss (EPA 402-F-00-009)
An EPA article [26,27] provides the subsequent inferences:
A research was undertaken in Europe, including 800 students from eight varied
schools, to gauge student performance linked to the indoor air quality.
The gathered data showed health issues and the skill of the student to focus as
linked to CO2 calculations in the classroom.
A health questionnaire was handed out to the students; this recorded the data
following which a computer-based program was used to rank their skill to focus.
It was discovered that the students’ ranking were low in those classrooms that
had high levels of CO2 (low ventilation rates); further, their health signs in such
classrooms were also very high.
The data inferred that inadequate quality of IAQ would lower the skill of a
person to execute particular mental jobs which needed focus or calculation or
memory.
There was statistical importance accorded to these tests and they validated that
managing IAQ encompassed regulating the source and providing sufficient
ventilation which in turn, enhanced the performance of the students.
It is the exhaled breath that is the primary source of CO2 and ventilation is the
fundamental method to eradicate the same. Low rates of ventilation are clearly
indicated by high levels of CO2 in classrooms. This can be corrected by suitable
checking the CO2 levels which consequently provides the zone good quality of
indoor air.
3.2. The relationship between functioning and ventilation
Two analyses lately conducted have validated the link between student attendance,
classroom performance and ventilation. The first research by Shendell et al. [28], recorded
the links amongst classroom attendance in Washington and Idaho and CO2 intensities,
which were employed as a substitute for ventilation rates. Student absences were
discovered to be 10%–20% higher for classrooms where the variation between indoor and
outdoor CO2 intensities surpassed 1000 ppm (1800 mg/m3), in contrast to classrooms
where the variations in CO2 intensities was less than (1800 mg/m3). The next research [29]
analysed the performance in school in a regulated classroom scenario in Denmark where
in there was a difference in the ventilation and temperature. The intensity of CO2
production using non-dispersive IR CO2 logger for the measurement of different condition
like the physical and the mental stress, relaxation for a particular school buildings were
measured. The measurement of the CO2 production for mental stress is 24% higher and
physical stress is 2.5 times higher than compared to the relaxation levels. The CO2
concentration is found to be 2100 ppm when the classes were ventilated between the
classes. Further, the mental concentration levels were tested for the seventh grade school
students with varying CO2 concentrations and the results revealed that when the students
were provided with the five letter words anagrams under 1000 ppm and above 2000 ppm
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Indoor Air Quality, Ventilation and Carbon Dioxide
concentrations of CO2, the number of correct answers reduced and the number of errors
increased when the concentration of CO2 level were above 2000 ppm [30]. The
concentration levels of CO2 were measured in primary school classrooms in Scotland. The
measurement was done in 60 classrooms over a period of 3-5 days. This test was
performed regarding the annual attendance, socio-economic status and the size of class
room. The results indicated that the decreased attendance as well as health issues of
students were related to CO2 concentration levels above 1000 ppm [31]. According to the
researchers, a rise in the supply rate of outdoor air and lowering of somewhat higher
classrooms radically enhanced the performance of several tasks, chiefly in context of how
fast every student could work (speed) in addition to few tasks in context of how many
mistakes were made (% mistakes, the ratio of replies that were mistakes). The
enhancement was statistically important at the level of P ≤ 0.05.
4. Discussion
It is difficult to plan and develop suitable environments for air quality and air quantity as
air is undetectable. CO2 levels accord adequate information related to indoor air quality.
Examining the CO2 levels is essential to identify the indoor air quality in any zone. The
need is magnified, when the area is a teaching area, particularly where it has an early
childhood learning setting, mainly because the young kids are more vulnerable to the
impacts of bad indoor air quality. Planners who know about IAQ issues will always
design spaces that permit higher values of CFM (cubic feet per minute) than what is
needed to ensure that ventilation levels exceed the agreed criteria. Designers during the
1960’s generally planned spaces that allowed an indoor air rate of 30 CFM per individual;
this reduced to 5 CFM when dealing with the energy predicament in the initial 1970’s.
This figure has presently been amended to 15 CFM. The systems and spaces are required
to be planned in a manner that they attain the higher values as required by the children.
Creative planners would be pre-emptive in using higher ventilation rates to guarantee that
the space provides the highest possible quality of indoor air. Examining the levels of CO2
is essential to sustain high quality of indoor air in the classroom.
The extant calculations of ventilation rates and CO2 concentrations in schools indicate
that, if we depend on the present ASHRAE ventilation criteria, several classrooms are
insufficiently ventilated. Despite, the outcomes from some of the researches in schools
being unreliable in linking ventilation rates or CO2 concentrations and signs; an extensive
literature assessment for indoor environments overall recommends a reliable association
[32]. These inferences, mainly in the grown-ups, would also relate to school children with
two justifiable postulations: that the exposures in offices linked to ventilation rates are
akin to exposures in the schools, and that the children are at least as susceptible as adults
to such exposures. The inferences made by Seppanen et al., together with the information
related to ventilation insufficiency in present schools, soundly recommend a pervasive
environmental insufficiency in schools is most probably linked to enhanced illnesses.
Hence, techniques to regulate encompass using proper fixtures and finish materials to
N. L. Sireesha J. Sci. Res. 9(2), 179-192 (2017)
191
keep contamination sources outside the school building, utilising exhaust fans to seize and
eradicate contaminants, and regulating pressures amongst areas to limit the migration of
contaminants to occupied or delicate domains. According to the good practices, it is
recommended that one needs to eliminate, eradicate and also mitigate contaminants that
allegedly have the possibility to lead to well-being issues or impact functioning and
relaxation.
5. Conclusion
The present study makes it evident that there is limited information pertaining to IAQ in
schools. The sole exclusion is the initial National Institute for Occupational Safety and
Health (NIOSH) analysis that is not even mentioned in the literature assessed; furthermore
no other studies have consistently analysed IAQ and health results in the schools. Several
of the researches have overlooked the thoroughness and quality that was essential to
handle the issue. There was a requirement to undertake more studies that analysed the
correlation amongst indications and that gauged exposures to several particular
contaminants. Additionally, there was a need to collect quantitative data relating to
exposure-well-being answer associations for particular contaminants that allegedly result
in well-being indicators, so as to offer a robust base to develop criteria for schools and to
ensure reasonably priced improvement methods. There is a requirement for enhanced
techniques for calculating exposure, especially those that offer more details of fungi and
bacteria and extended time for conducting the sample studies. The degree of the issue still
remains unidentified despite it being proved that several schools have insufficient
ventilation.
There is a need to meticulously and carefully gauge the ventilation rates and/or CO2
levels in a symbolic sample of schools; this would offer the essential details required on
the sections of schools dealing with the issue. To conclude, despite more research required
to ascertain the degree of IAQ issues in schools, it is proved that the ventilation rates in
new and extant schools fails to even meet the bare minimum ASHRAE criteria; this is the
cause for a crucial rise in signs amongst both school teachers and school children. It is
evident that programs need to be initiated to guarantee that much needed ventilation is
offered by all the schools.
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