Air pollution is an expression used to describe a state when the chemicals, particulate matter, or biological materials exceeds the recommended levels and become a source that harm effects or cause discomfort to humans and other organisms, or cause damages to the living natural environment. Pollution can be resulted from man-made daily industrial processes and activities or by the nature. There are many forms of pollutants solid particles, liquid droplets, or gases. Indoor air pollution can be arises from indoor and outdoor pollutant sources.

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People, especially students, spend about 90% of their live in enclosed controlled environments. These closed enclosed environments could have short or long terms of harm health effects on occupants according to the quality of the inside air (pollution levels). In recent years, the issue of indoor air and its quality (IAQ) has become an internationally recognized issue that caught the attention of researchers and the occupants toward improving the quality of air inside buildings environments. Fanger (2006) defines the indoor air quality (IAQ) as “the desire of human to perceive the air as fresh and pleasant, with no negative impacts on their heath and productivity”. Many researchers such as Wark and Warner (1981) investigated the sources of the outdoor and the indoor pollution that affected the indoor air. They found that the indoor air quality can be influenced by the outdoor air pollution sources such as traffic; industrial; construction, and combustion activities and the indoor sources such as ventilation equipment, furnishings, and human activities.
Common Indoor Air Pollutants
In this section, a total of 11 common indoor air quality parameters and its outdoor and indoor source in addition to it is health hazard on human shall be discussed. The IAQ parameters consists of three physical parameters (room temperature, relative humidity, and air movement) related to occupants’ thermal comfort which is defined in the previous section, nine chemical parameters (sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), carbon dioxide (CO2), particulates matters (PM), formaldehyde (HCHO) , radon (Rn) and ozone (O3)).In addition to the discussion of microbiological parameters (airborne bacteria, viruses, fungi and pollen), dust, odors and hydrocarbons.
Sulfur dioxide (SO2)
This type of pollutant gas has been extensively studied by many researchers around the world in outdoors environments due to it is high tendency to react with wide range of chemicals. SO2 is a colorless gas with a characteristic pungent odor and results from the fossil fuels combustion. Acid rain is one of the outdoor pollution problem cased by this gas.
Indoor SO2 concentrations are usually lower than outdoor, probably around 0.1 ppm, (Andersen 1972; Yocom, 1982 and Meyer, 1983). Due to it tendency to react with many chemicals, indoor SO2 can reacts with building materials and absorbed by the building surfaces (Andersen 1972). This gas can dissolves in water and mixes with air in all temperatures. The main indoor sources of SO2 are coal burning inside fireplaces and using fuel oil stoves and heaters. Sulfur dioxide causes headache, general discomfort, anxiety, and inflammation of the respiratory tract, wheezing, lung damage, and irritation of the eyes, nose and throat, choking and coughing.
Nitrogen dioxide (NO2)
Nitrogen dioxide is formed in outdoor atmosphere from high temperature combustion processes by the reaction of the nitric oxide (NO) with Oxygen (O2) and Ozone (O3). Motor vehicles contribute to about 55% of the manmade NOx emissions, EPA (2008). The major sources of this gas in indoors environments are gas cooking stoves and heater and tobacco smoke. In a study done by Yocom (1982) among British school children it was found that students whom suffer from reduced respiratory function are living in houses with gas stoves.
Exposure to low levels of Nitrogen dioxide (NO2) causes shortness of breath, tiredness, nausea and irritation to the eyes, nose, throat, and lungs; exposure to high levels cause rapid burning, spasms, swelling of tissues in the throat and upper respiratory tract, reduced oxygenation of body tissues, a build-up of fluid in the lungs, and may lead to death.
Carbon monoxide (CO)
CO is a very poisonous and non irritating gas that has no color, odor or taste. This gas produced by the incomplete combustion of carbon-based fuels (Yocom, 1982 and Meyer, 1983). Vehicular exhaust is a major source of carbon monoxide, EPA (2008). The indoor carbon monoxide concentrations are often higher than the outdoor concentrations due to the emission from gas stoves and tobacco smoke, Yocom (1982). The main effect of this gas on human health is its affinity for hemoglobin in blood. The inhaled CO mixes with the hemoglobin in the blood and forms carboxyhemoglobin that reduces the oxygen carrying capacity of the blood vessels. CO is 250 times more efficient at hemoglobin binding than Oxygen. Exposure to carbon monoxide causes headaches, shortness of breath, muscle aches, chest pain, especially in people with previous heart problems history, blurry vision, dizziness, nausea/vomiting, weakness, confusion, fatigue, rapid heart rate at high levels, fast deep breathing at high levels, fainting and death at high levels [CPSC Document #466, 2008].
Carbon dioxide (CO2)
Carbon dioxide is a colorless, odorless greenhouse gas emitted from the complete combustion of the carbon with Oxygen. The average typical concentrations of CO2 in the outdoor environment are 350-400 ppm, where the indoor concentrations are higher than those of the outdoor. The principal sources of the indoor CO2 are human body through the metabolism process (food consumption), and occupants’ activity.
The health problems associated with carbon dioxide exposure are headaches, dizziness, restlessness, feeling of an inability to breathe, malaise (vague feeling of discomfort), increased heart rate, increased blood pressure, visual distortion, impaired hearing, nausea/vomiting, loss of consciousness, coma, convulsions, death from asphyxiation (body cells do not get the oxygen they need to live).
Particulate matter (PM)
Particulate matter (PM) or fine particles are a mixture of tiny solid particles of solid and liquid droplets suspended in air. Particulate matter can be generated from man made (fossil fuels combustion processes) or natural (volcanoes, dust storms, and forest and grassland fires). There are many sources of the indoor particles such as pets, gas stoves, and tobacco smoke. Particles classified according to its size as fine particles are those whose size is smaller than 2.5 μm and coarse particles are those which are larger than 2.5 μm. Heinrich and Slama (2007) argued that the fine particles are the major threat source that affects the children health, where exposing to fine particles can results in cardiac and respiratory problems, [Dockery et al. (1993), Dockery and Pope (1994), Pope et al. (2002), Wu et al. (2005), Gilliland et al. (2005)]. The PM metals components are a major source that involves in the development of pulmonary, cardiovascular and allergic diseases, Schwarze et al. (2006). Exposure to high levels of fine particles causes health hazards such as heart diseases; respiratory diseases; altered lung functions, especially in children, and lung cancer and death.
Formaldehyde (HCHO)
Formaldehyde is a colorless with a strong pungent odor and considered as the most important substance in the aldehydes group due to it is mostly used in the production process of many building materials such as foam insulation, plywood, carpets, combustion appliances and particle board adhesives which releases again the formaldehyde to the indoor environment. The typical indoor formaldehyde concentrations range from 0.05 to 1 ppm, where in the new buildings the indoor levels of the formaldehyde are high, (Meyer, 1983; Samet et al., 1991) and most of the complains were from buildings with formaldehyde foam insulation and mobile homes that uses plywood paneling, Wadden (1983). The rate of diffusion of this substance is a function of the indoor temperature and humidity. Exposing to formaldehyde can cause health effects include eye, nose, and throat irritation; wheezing and coughing; fatigue; skin rash; severe allergic reactions, EPA (2008). High concentrations of formaldehyde may cause cancer and other effects listed under organic gases.
Radon (Rn)
Radon is an inert radioactive, colorless, odorless, tasteless noble chemical gas element. Naturally, this element can be found as soil gas contained radon formed from the decay product of uranium and can remains as a gas under normal environmental conditions. This contaminant element can be found indoors due to some sources such as building materials especially that rich with radium, such as alum shale-based material and phosphogypsum wallboard, deep wells water natural gas having high radon concentrations. Another principal source is the flow of the soil gas into the homes through building cracks, sumps and any other openings or around the concrete slab, Bale (1980) Handbook ch. 40. Due to tightness of the buildings design, the indoor concentrations are usually higher than that in outdoor environment. Recently, this element is considered as carcinogen element du to it is radioactivity, which has a vital health hazard on buildings occupants, where it is considered to be the second most reason of lung cancer after cigarette smoking, EPA (2008).
Ozone (O3)
Ozone is a very reactive pollutant that can oxidizes most of the chemicals in nature such as aldehydes. In natural outdoor environment, Ozone produces from the effect of the sunlight on the nitrogen oxides and hydrocarbons. Usually the Ozone concentrations in the outdoor environment are higher than that found in indoors. The main sources of the high indoor Ozone concentration are the photocopy machines, laser printers, electrostatic air cleaners and x-ray generators, (Yocom, 1982 and Wadden, 1983). These sources develop electrostatic fields that can generate highly toxic concentrations of ozone in air. Exposing to low concentration levels of Ozone can cause eye irritation, visual disturbances, headaches, dizziness, mouth and throat irritation, chest pain, insomnia, breath shortness and coughing (Sittig 1991), where exposure to high levels of ozone can reduce lung function or respiratory problems, such as asthma or bronchitis.
Microbiological Parameters
Fungi, molds, viruses, bacteria and pollen are types of the microbiological indoor contaminants. The major sources of these contaminants are human, animals and plants and it can be found anywhere these sources are available, Meyer (1983). Due to the insufficient maintenance of the HVAC system parts (condensers, cooling coils, ducts and drainage pans) it can be another source of contamination by encouraging the proliferation of the microbes, (Wark and Warner, 1981 and Samet et al., 1991). The concentrations of the indoor microbes are higher than that in the outdoor environment due to the building tightness and the source availability.
Dust
ASHRAE (2009) defines dust as “solid particles projected into air by natural forces such as wind, volcanic eruption, earthquakes, or by mechanical processes including crushing, grinding, demolition, blasting, screening, drilling, shoveling and sweeping”. Dust immigrates from outside to inside environment by infiltration air through the building’s crack, unsealed windows and doors and through the ventilation system. Dust has health effects on people with ultra-sensitive lungs such as people with asthma, young children and elderly people. Dust causes discomfort for people and damages home furniture and household equipment.
Odors
Indoor odors are arising from occupant’s body and their indoor activities such as smoking, cooking, garbage, sewage and industrial processes. The human body normally dissipates around 200 types of chemicals which are responsible for the human odors, (Meyer, 1983). Odors do not have any major effects on the occupant’s health, but it causes discomfort sensation to the occupants which make it as a sign of the poor indoor air quality.
Hydrocarbons
Most of the indoor hydrocarbons sources are results from the different housekeeping materials such as widows, oven, drain, clothing cleaners, paint solvent and human use materials such as deodorants, shaving creams, hair sprays and air refreshers sprays. The indoor hydrocarbons levels reach high levels when housekeeping is in progress, Meyer (1983). The indoor cooking gas (mostly Propane gas) is considered also a major source of the indoor hydrocarbons which may results in serious fire accidents or death due to insufficient maintenance or checking for the gas burner and cooking equipment, Meyer (1983).
During this study, the CO2 contaminant will be studied to investigate the indoor air quality inside Kuwaiti’s classrooms. The indoor concentration of carbon dioxide (CO2) has often been used as a surrogate for the ventilation rate per occupant, (Lee and Chang, 1999 and Daisey et al., 2003), where providing good ventilation rates with sufficient amounts of fresh air can dilutes and reduces the concentrations levels of indoor air pollution generated by the different indoor pollutants sources.
International and Kuwait Indoor Air Quality Standards and Regulations
Since the last decade, researchers were interested to investigate the indoor air pollution for different indoor environments and the contaminant sources to indicate the acceptable indoor concentration levels for these pollutants. As a result of these researches, many IAQ standards and regulations have been developed and established by different organizations indicates the recommended acceptable concentrations levels for these indoor pollutants. These standards are established according to the purpose and activity of the indoor zone and characteristics of it is users or occupants. For this reason, sometimes it can be found some differences in values for the same pollutant. A summary of the common indoor air pollutants standards are given in Table 3.1.
Table 3.1: International and Kuwait Standards and Guidelines for Common Indoor Air Pollutants, (in ppm).
NIOSH
(1992)
Canadian
(1995)
OSHA
MAK
(2000)
NAAOS/EPA
(2000)
WHO-Europe
(2000)
ACGIH
(2001)
Hong Kong
(2003)
KW-EPA
(2001)
Sulfur
Dioxide
(SO2)
2 [8 hr]
5 [15 min]
0.019
0.38 [5 min]
5
0.5
1.0 [5 min]
0.14 [24 hr]
0.03 [1 yr]
0.047 [24 hr]
0.019 [1 yr]
2 [8 hr]
5 [15 min]
2 [8 hr]
5 [15 min]
Nitrogen
Dioxide
(NO2)
1.0
[15 min]
0.05
0.25 [1 hr]
5
[Ceiling]
5
10 [5 min]
0.05
[1 yr]
0.1 [1 hr]
0.02 [1 yr]
3
5 [15 min]
0.021 – 0.08
[ 8 hr]
0.026 – 0.08
[8 hr]
Carbon
Dioxide
(CO2)
5000
30000 [15 min]
3500
5000
5000
10000 [15 min]
5000
30000 [15 min]
800 – 1000
[8 hr]
600 – 1000
[8 hr]
Carbon
Monoxide
(CO)
35
200 [Ceiling]
11 [8 hr]
25 [1 hr]
50
30
60 [ 30 min]
9 [8 hr]
35 [1 hr]
86 [15 min]
51 [30 min]
25 [1 hr]
8.6 [8 hr]
25
1.7 / 8.7
[8 hr]
86 [15 min]
51 [30 min]
25 [1 hr]
8.6 [8 hr]
Particular
Matter
(0.1 mg/m3
[1 hr]
0.04 mg/m3
[8 hr]
5 mg/m3
1.5 mg/m3
For 35μg/m3[24hr]
15μg/m3[1 yr]
3 mg/m3
0.23 mg’m3
[24 hr]
0.07 mg/m3
[1 yr]
Formaldehyde
(HCHO)
0.016
0.1 [15 min]
0.1
0.04[8 hr]
0.75
2 [15 min]
0.3
1.0 [5 min]
0.4
0.081 [30 min]
0.3 [ceiling]
0.024 / 0.081
[8 hr]
0.08 [30 min]
Radon
(Rn)
800 Bq/m3e
4 pCi/L
[1 yr]
2.7 pCi/L
[1 yr]
4.1 – 5.4 pCi/L
[8 yr]
4 pCi/L
[1 yr]
Ozone
(O3)
0.1
[Ceiling]
0.12
[1 hr]
0.1
0.12 [1 hr]
0.08 [8 hr]
0.06
[8 hr]
0.05 – heavy work
0.2 – any work [2 hr]
0.025 – 0.061
[8 hr]
0.03 – 0.1
[8 hr]
Numbers in brackets [ ] refers to average time (min=minutes; hr=hours and yr=years)