Brief Guide to Air Pollutants & Where They Come From

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Air pollutants contain millions of contaminants that degrade the quality of air quality and can lead to dentrimental affects on human health. These contaminants can come to the conditioned space from outside or can be the product of some bacteria germinal activities inside the conditioned space itself. Here are some of the most common contaminants that are present in the air, where they come from, and how they can affect the occupant’s health and comfort.

Contaminants and their Sources

Here are some of the most common air pollutants, but this list is not exhaustive.

  • Allergens can come from dust, cooking exhaust, smoking fumes, tobacco smoke, moulds, pets and many other sources. They cause skin, sinus and eye irritation.
  • Bacteria and viruses can come from pets, moisture or accumulated water and human carriers.
  • Carbon dioxide, carbon monoxide, oxides of nitrogen and sulphur dioxide are few of the most poisonous gases having sources in incomplete combustion of fuels, burning of rubber and evaporation of stored chemicals.
  • Odoriferous chemicals are the product of inefficient cooking, decaying organic matter and burning or evaporation of chemicals.
  • Formaldehyde and volatile organic compounds have their sources in construction materials,furniture polishes and cleaning products.

Air Quality Effects on Health and Comfort

All these contaminants affect the health of the occupants in short or long run. The intensity of the effect on all the types of contaminants will not be same but will vary, for example some of the contaminants will render the occupants allergic, some may make the individual sick, and some may just be an unpleasant but harmless odor. In the next section I’ll group contaminats into categories depending on the intensity of the effect.

Contaminants Causing Short Term Effects

A high concentration of a particular gas in the conditioned areas can be fatal or even cause death. These types of fatal contaminants are carbon monoxide, bacteria and biological contaminants. Carbon monoxide is a colorless and odorless gas which is product of incomplete combustion of fuel oils or due to malfunctioning of combustion appliances. Combustion appliances in the conditioned area could be stove, water heater or furnace. It is also the main constituent of the exhaust of motor vehicles. It is the reason of thousands of deaths each year.

Certain disease causing bacteria get transmitted by air. One of such disease is tuberculosis. The bacteria causing tuberculosis is tubercle bacillus, which tends to stay afloat in air when exhaled by a diseased person. This can be prevented only by proper isolation and ventilation methods.

One more type of bacteria that can be extremely harmful for the people with weak immune system is legionella, bacteria that causes legionnaire’s disease. The bacteria multiply very easily in warm water and when the water is sprayed or splashed, the bacteria becomes airborne and gets into the lungs. The germinal sites of these kinds of bacteria are water coolers, cooling towers and domestic hot water systems.

The symptoms of the short term bacteria diseases are often unnoticeable and thus can be extremely fatal.


Carcinogens are pollutants that are known to contribute to cancer. There are often no symptons of ill health until the individual is affected with the disease. One of the most common sources of carcinogens are tabacco smoke, which can lead to lung and heart cancer.

Another carcinogen is the gas radon. It is found naturally, resulting from the decay of radium in the soil.

Contaminants Causing Detrimental Effects on Health

Air contaminants such as volatile organic compounds, bacteria, viruses, ozone, allergens etc can cause detrimental effects on health if not fatal. Such contaminants cause irritation of eyes, skin and mucous membrane. They produce rashes or result in cold like symptoms.

Annoying Contaminants

Many contaminants though not health hazardous may cause distraction or irritation to occupants. Contaminants like odoriferous chemicals, body odors, rotten food and molds are examples of narking contaminants


Fundamentals of HVAC system by Robert McDowall