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We all know that Outdoor air pollution can
have ill effects on our health. However many do not know that
Indoor air pollution can also cause considerable harmful effects
often much worse than Outdoor Pollutants.
The U.S. Environmental Protection Agency
(USEPA) studies of human exposure to air pollutants indicate that
indoor levels of pollutants may be 2-5 times, and occasionally
more than 100 times, higher than outdoor levels. These levels
of indoor air pollutants are disturbing as most of us modern urbanites
spend an estimated 90% of our time indoors.
Comparative risk studies performed by USEPA
and its Science Advisory Board have consistently ranked indoor
air pollution among the top five environmental health risks to
the public.
Indoor air contaminants can originate within
the building or be drawn in from outdoors. If pollutant sources
are not controlled, IAQ problems can arise, even if the Heating,
Ventilation & Air-Conditioning (HVAC) system is operating
properly.
There are four factors affecting IAQ :
| 1. |
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Source of indoor air pollutants |
| 2. |
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HVAC System Design and Operation |
| 3. |
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Pollutant Pathways and Driving Forces |
| 4. |
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Building occupants |
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(1) Source of Indoor Air Pollutants
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Particulate Matter; Dust, Smoke,
Soot |
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From the burning of wood, diesel and other fuels;
industrial plants; agriculture (field burning, plowing) and
unpaved roads. |
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Causes nose and throat irritation, bronchitis
and damage the respiratory system such as to the lungs. |
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Main source of haze which reduces visibility. |
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VOCs (Volatile Organic Compounds); Smog-formers |
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From burning of fuel, solvents, paints glues.
VOCs include chemicals such as methylene chloride, methyl
chloroform, toluene, and benzene. |
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In addition to ozone (smog) effects, many VOCs
can cause cancer. |
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Carbon Monoxide (CO) |
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From the burning of natural gas, coal, gasoline
and oil. |
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Reduces blood's ability to deliver oxygen to
body cells and tissues; cells and tissues need oxygen to work.
Carbon monoxide may be particularly hazardous to individuals
with heart or circulatory (blood vessel) problems and those
with damaged lungs or breathing passages. |
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Lead |
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From leaded paint (houses, cars), gasoline,
smelters (metal refineries) and manufacturing plants of lead
storage batteries. |
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Ill health effects on brain, digestive system
and other nervous system. |
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(2) Heating, Ventilation & Air-Conditioning (HVAC) System
Design and Operation
|
| A properly designed and functioning
HVAC system: |
| • |
Controls temperature and humidity to provide thermal comfort
- managing and maintaining the humidity and temperature at
an ideal level. |
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Distributes adequate amounts of outdoor air to meet ventilation
needs of occupants. Thus freshening the indoor air sufficiently
with outdoor air as opposed to recirculating increasingly
stale indoor air. |
| • |
Isolates and removes odors and pollutants through pressure
control, filtration, and exhaust fans. If the indoor pollutants
are not "purged", they will directly give rise to
what is popularly known as the Sick Building Syndrome. |
Not all HVAC systems are designed
to accomplish all of these functions. Some buildings rely only
on natural ventilation. Others lack mechanical cooling equipment,
and many function with little or no humidity control.
(3) Pollutant Pathways and Driving Forces
Airflow patterns in buildings
result from the combined forces of mechanical ventilation systems,
human activity, and natural effects. Air pressure differences
created by these forces move airborne pollutants from areas of
higher pressure to areas of lower pressure through any available
openings in building walls, ceilings, floors, doors, windows,
and HVAC system.
An inflated balloon is an excellent
example of this driving force. As long as the opening to the balloon
is kept shut, no air will flow, but when open, air will move from
inside (area of higher pressure) to the outside (area of lower
pressure).
(4) Building Occupants
Human activities can also have
effects on Indoor Air quality. A poorly ventilated gynasium with
the build up of perspiration and Carbon Dioxide would not be an
ideal place to exercise or to breathe fresh air.
High humidity caused by human
activities indoor is a direct contributor to mould build up. Indoor
fountains look great but the moisture from these fountains leaking
into floor and ceiling boards can hurt the building's occupants
in the long term.
Other activities such as cooking
or ozone build up from common office appliances such as laser
printers or photocopying machines can contribute to poor IAQ.
| Symptoms commonly attributed to IAQ problems
include: |
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headache, fatigue, and shortness of breath |
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sinus congestion, cough, and sneezing |
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eye, nose, throat, and skin irritation |
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dizziness and nausea |
Environmental stressors such
as improper lighting, noise, vibration, overcrowding, poor ergonomics,
and psychosocial problems (such as job or home stress) can produce
symptoms that are similar to those associated with poor air quality,
but require different solutions.
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