Although it is difficult to prove that specific health problems among indoor workers have particular causes, Indoor Air Quality (IAQ) has become a real occupational health issue.

IAQ is a suspect when building occupants experience one or several of the following symptoms: headaches, fatigue, shortness of breath, sinus congestion, coughing, sneezing, dizziness, nausea, and irritation to the skin, eyes, nose and throat. These symptoms can usually be attributed to inadequate temperature, lack of humidity or lighting; exposure to chemicals, dusts, gases, vapours and odours; or a lack of fresh air from the ventilation system. People generally develop symptoms within a few hours of starting the workday and feel better after leaving the building. Collectively, these symptoms are often referred to as "Sick Building Syndrome."

The reason IAQ problems are difficult to determine is that building occupants are exposed to not one but several adverse conditions. For example, you might not think that the slight emissions from furniture, carpets, photocopiers, or the perfume worn by your co-workers could be harmful, but in combination they can affect your health. Again, these effects are impossible to trace accurately, but the condition does have a name: Multiple Chemical Sensitivity (MCS).

The following is a list of common indoor air contaminants and their sources:

• Carbon dioxide, tobacco smoke, perfume, viruses, bacteria from building occupants
• Gases, vapours, odours from furniture, carpets and paints
• Dust, fibreglass, asbestos from building materials
• Toxic vapours, volatile organic compounds from cleansers, solvents, pesticides, disinfectants, glues
• Bacteria, spores, pollen, mites from damp areas and stagnant water
• Ozone from photocopiers, electric motors, electrostatic air cleaners

It is possible to control these contaminants by eliminating or isolating the source, or by maintaining a good, clean heating, ventilating and air conditioning (HVAC) system. If the HVAC system is functioning properly, it also regulates humidity, air velocity and temperature.

Consider the Total Indoor Environment. Besides the quality of indoor air, Total Indoor Environment also includes temperature, lighting and noise. In an office that is too warm, occupants feel tired; one that is too cold causes occupants' attention to drift, making them restless and easily distracted. Inadequate lighting affects people's vision. Loud or irritating noises affect concentration. These are all factors which can contribute to headaches, stress, and a variety of other problems.

You cannot take a tablet to cure Sick Building Syndrome. The surest way to control symptoms is to improve indoor air quality. It is often simply a matter of cleaning an air filter, regularly replacing the slime in a humidifier with clean water, or opening a window.

There are no occupational health and safety regulations for IAQ, however the Canadian Building Code recommends the American Society for Heating, Refrigeration and Air Conditioning Engineering (ASHRAE) 62-1989 as a guideline for ventilation and ASHRAE 59 for thermal comfort.