Pollutants can be organised into three categories:
1. those originating outside the living space
2. those released by things inside the living space
3. those resulting from human metabolism and activities.
Examples of 1: airborne mould spores and pollen, radon in the soil, vehicle exhaust, garden chemicals, outgassing and particulates from insulation
Solution: Separate - make sure your house is well air sealed. Gaseous and particulate pollutants travel into the living space primarily by moving on air currents through holes and gaps in the structure.
Examples of 2: outgassing or particulates released from home furnishings or building materials directly exposed to the interior living space (paints, wall paneling, cabinetry, etc.), evaporation from cleaning and home-maintenance products, mould spores from colonies growing within the house, pollen from house plants
Solution: Eliminate - use less polluting alternatives. Choose low-outgassing paints and finishes, furniture without long-term formaldehyde emissions, less-noxious cleaning products. Find sources of moisture and fix them.
Examples of 3: carbon dioxide, ammonia, methane, water vapor
Solution: Ventilate - that means controlled air change.. NOT relying on air change through permanent gaps and cracks in the building envelope! Local ventilation (exhaust fans) should be used intermittently to reduce humidity levels in kitchens and bathrooms quickly, while general ventilation should be ongoing in order to change the air in the entire house. Controlled ventilation can be passive ie. by opening windows, doors or vents. Mechanical ventilation is required in very air tight houses in cold climates.
Find out more in the article 'Improving Indoor Air Quality - What Works' published by the Healthy House Institute. Or check out the terrific 'Is Your House Killing You?' web site.