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Indoor Air Quality (IAQ)

Most building occupants are aware of the health and comfort effects of IAQ. Specific strategies to improve air quality will vary depending on the occupant's comfort threshold and activities, the degree of ventilation flexibility within the building, and internal conditions as well as outdoor conditions, such as temperature, humidity, etc.

IAQ refers to the physical, chemical and biological characteristics of indoor air in non-residential workplaces with no industrial processes or operations which can affect the comfort or health of the occupant.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 62-1989 defines acceptable IAQ as indoor air that contains no excessive concentrations of contaminants and causes dissatisfaction to no more than 20 percent of a building's occupants.

HEALTH:    Health refers to a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

COMFORT:    Comfort is a subjective assessment of the whole environment where thermal, acoustic, air quality and visual factors are all considered.

IAQ in is affected by factors which include:

bullet number of occupants in the room or building,
bullet activity of the occupants,
bullet type and amount of contaminants being generated by activities, processes, etc.
bullet lack of ventilation
bullet type and efficiency of available ventilation
bullet type, structure and age of a building,
bullet type of building materials,
bullet building's state of repair,
bullet outdoor air quality and conditions such as temperature, wind velocity and direction, relative humidity, and barometric pressure

The link between human shelter and the quality of indoor air is not new - even caves had IAQ problems. More recently, energy conservation measures have contributed to an increase in IAQ problems. During the 1970s, buildings were planned and renovated to reduce outside air infiltration. Windows were sealed to prevent costly heated or cooled air from escaping to the outdoors. The goal was to create an air-tight building which would reduce heat loss and conserve energy. An unfortunate side effect of these measures is a decrease in the volume of fresh air circulated. However, properly thought out energy conservation initiatives are not synonymous with poor IAQ.

IAQ problems can be divided into two categories; thermal environment, and air contaminants. Thermal environment refers to such variables as air temperature, humidity, air movement, uniformity of air temperature, and temperature of surrounding surfaces (e.g. walls, chairs or floors). These variables affect the level of human comfort or discomfort. In extreme cases, the thermal environment may contribute to health risk from heat stroke, etc.

A thermal complaint may be caused by outdoor conditions, drafts, uneven heating and cooling, temperature stratification, the proximity of an individual to a heat source, or any combination of the above. There may be other associated factors such as poor air circulation, lack of ventilation, improper clothing, change in activity level and so on.

Thermal variables, generally, have acceptable ranges. Air temperature of 22-26C (summer) and 20-24 C(winter) are recommended by ASHRAE to satisfy 80% of the population. This is not to suggest that if thermostats are set anywhere within the recommended range, eight out of ten people will be satisfied.

The acceptable range for indoor relative humidity is 25 - 60%. Over-heating the room or building may result in complaints caused by low relative humidity, unless humidity levels are maintained. It is advisable to adjust the temperature to the low end of the acceptable range to maintain relative humidity and comfort levels. Additional clothing, such as a sweater or jacket, can be worn, if needed.

Air contaminants consist of numerous particulates, fibers, mists, fumes, bioaerosols and gases, some of which can impair human performance. High concentrations of contaminants may present a full range of health risks from mild irritation of the upper respiratory system to a serious health threat (acute). Long term exposure to low concentrations of contaminants may impact health as well (chronic).

Air contaminants are part of today's technology. Adequate fresh air is vital, however, additional measures should be taken to eliminate, reduce or control indoor air pollutants. Because IAQ is affected by various factors, improvement strategies are diverse.

IAQ Assessment

 IAQ assessment may include the following tests:

bullet carbon dioxide (CO2)
bullet temperature
bullet relative humidity
bullet carbon monoxide (CO)
bullet combustion products
bullet oxygen (O2)
bullet air flow/exchange rate
bullet microbials

Additional information and investigations may be required  to supplement the assessment.  Physician confirmed illnesses, consistent with exposure to moulds, will be assessed following the Health Canada Protocol (1995).


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