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					           Indoor Air Quality



                  Department of Civil and Environmental System Engineering
                               University of Incheon, South Korea




                                      Abstract
 People spend most of their time indoors; thus, most of their exposure to pollution
occurs indoors. Indoor air contains many of same pollutants as does outdoor air, but
pollution concentrations in indoor and outdoor air usually differ. Indoor mixing ratios of
ozone and sulfur dioxide are usually less than are those outdoors, but indoor mixing
ratios of formaldehyde are greater than are those outdoors. So Indoor Air Quality is very
important. This study finds out what is Indoor Air Quality and introduces factors that
decrease Indoor Air Quality. It researches relation among factors influencing indoor air
quality through box model.


             <Contents>
 - Introduction
 Importance of indoor air quality
 Introduction related theory
 - Main subject
 Indoor air pollutant and pollution source
 Factors Influencing indoor air quality
 Effect of Indoor air pollutant
 Result
 - Conclusion
 - Reference



                                               1
1. Introduction
1-1 What is Indoor Air Quality?
-It is defined as the amount of pollutant or contaminations on the indoor air.
-Gases or particulate matter harmful to human and nature is called pollutant.
-Indoor Air Quality degraded by ourselves directly or indirectly.
-It reduces by many factors such as smoking, dust, mites, mold spores, radon, and
 gasses and chemicals from materials and appliance.


1-2 Importance of indoor air quality
  We spend about 90% of our time indoors in our homes, cars, office, factories, public
buildings such as restaurants, malls, and others. Dilution rates of atmospheric pollution
are very high, but dilution rates of indoor air pollution are very low. Without proper
ventilation, concentration of indoor air will increase if so that has negative influence on
human. Because people spend most of their time indoors, it is useful to examine the
composition and quality of indoor air. Because people’s time is often divided between
home and work, it is important to examine air quality in both residences and workplace.
Sources of indoor air pollution include outdoor air and indoor emissions. Outdoor air
contains the constituents of smog, but some of these constituents dissipate quickly
indoors because of the lack of ultraviolet radiation to reproduce them indoors. .



 1-2. related theory

 Box model 이란?
   This study establishes expression that is about matter of income and outgo. It suppose
 that concentrations of input, inside pollution and output are equal each other in control
 box.
                                                                 Ci = initial concentration
                                                                 S= Source
                                                                 V= volume of box
                                          V                      Q= amount of air
                                                       C2
                                          C                      C= concentration
                                                       Q2
        C1                                                       C1, Q1=input
        Q1                                                       C1, Q1=output


                                  S




                                              2
              C  Ci * e  Qt / V  ( S  Q * C0 ) / Q * (1  e  Qt / V )

2. Main subject
2-1 Indoor air pollutants and pollution source
 About 89 percent of people’s time is spent indoor, 6 percent is spent in vehicles, and 5
percent is spent outdoors. Another study found that in nonindustrialized countries,
people in urban areas spends 79 percent of their time indoors and those in rural areas
spend 65 percent of their time indoors. Because people breathe indoor air more than
outdoor air, an examination of indoor air is warranted. This table identifies major
pollutants in indoor air and their primary sources. Many of the pollutant gases in door
air also found in outdoor air. Outdoor pollutants enter indoor air by infiltration, natural
ventilation, and forced ventilation. Infiltration is natural it exchange through cracks and
leaks, such as through door and window frames, chimneys, exhaust vents, ducts,
plumbing passages, and electrical outlets. Natural ventilation is air exchange resulting
from the opening or closing of windows or doors to enhance the circulation of air.
Forced ventilation is the air exchange resulting from the use of whole-house fans or
blowers




           pollutant                                                   Source
 Combustion gases-CO,NO                      Combustion-furnace, cooking stove, space
                                                                    heater, etc.
      Volatile organic                   Out gassing of building materials, coatings, wall
     compounds(VOCs)                              and floor coverings, and furnishings
          Fomaldehyde                      Out gassing of pressed wood, insulation foam
             ozone                                          Duplicator, Air cleaner
 Biological agents-molds,                       Contaminated ventilation systems, pets
       spores, danger
  Environmental tobacco                                       Smoking in building
            smoke
            Radon                               Infiltration from soil beneath structure
     Particulate matter                                             Combustion
           Asbestos                              Construction coatings, tile, insulation
            (Important Indoor Air pollutants and Their Emission Source)




                                                      3
 2-2 Factors influencing indoor air quality
 Several factors influence the quality if air indoors: the rate if exchange of air with air
from outdoors, the concentration of pollutants in outdoor air, the rate of emissions
from sources indoors, the rate of infiltration from soil gases, and the rate of removal in
the indoor environment.
  The source of indoor air pollutants may be inside the building, or they may be
transported into the interior space from the outside, Sources located indoors include
building materials, combustion sources, furnishings, and pets. Emissions of organic
gases are higher with increased temperature and humidity but usually decrease with
age if the structure or furnishings. Construction materials and the composition of
furnishings inside the building may give off or outgas pollutants into the interior
airspace, e.g., glues or adhesives. Natural gas for cooking and kerosene space heaters
release NO and CO2 even when operating properly. Molds may grow in the ventilation
ducts and be distributed throughout a building.
  Radon from the soil can enter buildings through cracks in the foundation when the
pressure inside is lower than in the soil. The rate of infiltration depends on the soil
type, the building structure, and the pressure differential between the soil and the
building.
 Air is exchanged between indoors and outdoors by several ways: nateuaventilation,
mechanical ventilation, and infiltration or exhilaration. Natural ventilation, mechanical



                                            4
 ventilation, and involves fans and heating and air-conditioning system, Infiltration and
 exhilaration represents undesirable movement of air in and out of the structure.
 Buildings are characterized as “tight” when in filtration rates are low.




<Representation of home with various sources and sinks for indoor air pollutants>

(A), exchanges; (B), indoor concentration; (C), out gassing of building and furniture materials;

(D), infiltration from soils; (E), removal on interior surfaces.



 The air exchange rate influences the concentration of indoor pollutants in two ways. At
higher air exchange rates, the pollutants inside a structure are removed from the
interior, As long as the ambient outside air has pollutant levels. However, if the
pollutant concentration outside is elevated, building; e.g., an idling vehicle adjacent to
an air intake will transfer exhaust fumes into the building can contribute to higher levels
of indoor pollutants.
 The concentration of indoor pollutants is a function of removal processes such as
dilution, filtration, and destruction. Dilution is a function of the air exchange rate and the
ambient air quality. Gases and particulate matter may also be removed from indoor air
by deposition on surface. Filtration systems are part of ventilation systems. As air is
circulated by the air-conditioning system it passes though a filter which can remove
some of the particulate matter. The removal efficiency depends on particle size. In
addition, some reactive gases like NO2 and SO2 are readily adsorbed on interior
surfaces of a building or home.


2-3. Effect of Indoor air pollutant
1. Carbon Dioxide
 Carbon Dioxide (Co2(g)) is present in background air and produced indoors from
breathing and combustion. Outdoor mixing ratios of (Co2(g)) are too low to cause
noticeable health problems. Indoor air, (Co2(g)) mixing ratios may build up enough to
cause some discomfort, but those higher than 15,000 ppmv are necessary to affect




                                                          5
human respiration. Mixing ratios higher than 30,000 ppmv are necessary to cause
headaches, dizziness, or nausea. Such mixing ratio do not generally occur.


2. Carbon Monoxide
 Exposure to 300 ppmv of Co(g) for one hour causes headaches; exposure to 700 ppmv
of Co (g) for one hour causes death, (Co (g)) poisoning occur when it dissolves in blood
and replaces oxygen as an attachment to hemoglobin [Hb(aq)], an iron-containing
compound. The conversion of O2hb(aq) to COHb(aq) (carboxyhemoglobin) cause
suffocation. Co(g) can also interfere with O2(g) diffusion in cellular mitochondria and with
intracellular oxidation. For the most part, the effects of Co (g) are reversible once
exposure to Co(g) is reduced.


3. Sulfur Dioxide
Because So2(g) is soluble, it is absorbed in the mucous membranes of the nose and
respiratory tract. Sulfuric acid [H2SO4(aq)] is also soluble, but its deposition rate into
the respiratory tract depends on the size of the particle in which it dissolves. High
concentrations of So2(g) and [H2SO4(aq)] can harm the lungs. Bronchiolar concentration
and respiratory infections can occur at mixing ratios greater than 1.5 ppmv. Long-term
exposure to So2(g) from coal burning is associated with impaired ling function and other
respiratory ailments. People exposed to open coal fires emitting SO2(g) are likely to
duffer from breathlessness and wheezing more than are those not exposed to such fires.


4. Formaldehyde
 Formaldehyde[HCHO(g)], produced during biomass burning and chemical reaction
outdoors, is emitted from particleboard, insulation, furnishings, paneling, plywood,
carpets, ceiling tile, and tobacco smoke indoor. Formaldehyde mixing ratios indoors are
usually greater than are those outdoor. It also removed by deposition to the ground and
reaction whit wall. floor, and ceiling surface. Formaldehyde cause skin stimulus and
lung cancer.


5. Radon
  Radon is a radioactive but chemically uncreative, colorless, tasteless, and odorless
gas that forms naturally in soils. Its decay products are believed to be carcinogenic and
have been measured in high concentrations near uranium mines and in houses overlying
soils with uranium-rich rocks. The combination of radon and cigarette smoking is
expected to increases lung cancer risks above the normal risks associated with smoking.



                                             6
6. Nitrogen Dioxide
Nitrogen Dioxide [NO2(g)] is produced chemically from oxidation of nitric oxide
[NO2(g)] and is emitted in small quantities indoors. Although exposure to high mixing
ratios of NO2(g) harms the lung and increase respiratory infections, epidemiologic
evidence indicates that exposure to typical mixing ratios of NO2(g) has little effect on
the general population.


7. Asbestos
 Asbestos is a class of natural impure hydrated silicate minerals that can be separated
into flexible fibers. People who were most likely to be exposed to asbestos in the past
were miners, insulation manufacturers, and insulation installers.
 The primary health effects of asbestos exposure are lung cancer, mesothelioma, and
asbestosis. Mesothelioma is a cancer of the mesothelial membrane lining the lungs, and
asbestosis is a slow, debilitating disease of the lungs.


8. Volatile Organic Compounds
1) Benzene
  Benzene’s effects are respiratory irritation, dizziness, headache, nausea, chromosome
aberrations and leukemia. The important sources are gasoline combustion, tobacco
smoke and solvents.
2) Toluene
 Toluene’s effects are skin and eye irritation, fatigue, nausea, confusion, fetal toxicity, anemia,
liver damage, dysfunction of central nervous system, coma, and death. Sources of toluene are
gasoline combustion, biomass burning, petroleum refining, building materials.


              Pollutant                                            Effect
    Combustion gases-CO,NO                     Headache, vertigo, emesis, lung disease
Volatile organic compounds(VOCs)                         the production of cancer
             Fomaldehyde                                 skin stimulus ,lung cancer
                ozone                               stimulus on the respiratory organs
Biological agents-molds, spores,                    allergic disease, respiratory disease
               danger
  Environmental tobacco smoke                   Anxiousness, lung disease, lung cancer
               Radon                                            lung cancer
         Particulate matter                stimulus on the respiratory organs and      mucous
                                                 membrane, the production of cancer



                                                7
                    Asbestos                                          skin stimulus ,lung cancer
                                          <Effect of Indoor air pollutant>
2-4. Application of related theory and result

C  Ci * e Qt / V  ( S  C1 ) / Q * (1  e Qt / V )


<Optional Value substitute for that expression.>


                                                                        12
Ci  5ug / m 3
                                                                        10
C1  10ug / m 3                                                f ( t)   8
Q  10.0m                      3
                                   / sec                                6
                                                                        4
V  100m                   3
                                                                             0       50   100

                                                                                     t



1) when V                V/2


f ( t)                                                       f ( t)



                t                                                                t



2) when C                C/2


f ( t)                                                       f ( t)



                t                                                                t



3) When Q                 Q/2


f ( t)                                                       f ( t)



                t                                                                t




                                                         8
(Result)
- (V) is not related to (C), but inverse proportion with diffusion velocity
- If decrease in a half of outdoor concentration, indoor concentration also decrease.
- If decrease in a half of amount of ventilation, indoor concentration increase.


3. Conclusion
- Proper ventilation is important for indoor air quality.
- Reduction of the pollutant source reduces the concentration of pollution to indoor air.
- Different types of pollutant have different level of harm to human health
- The increase of pollution level like smog and particle in indoor air cause direct health
     effect and can reduce easily than others like VOC’s.


4.   Reference
Mark Z.Jacobson, Atmospheric Pollution.
Richard W.Boubel, Fundamentals of Air Pollution.
대기환경연구회, 대기환경개론, 2003




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