There are several kinds of air pollutants in homes. The following are some common sources.

• burning of fuels in gas stoves
• building and furnishing materials
• renovation works
• new wooden furniture
• consumer products containing volatile organic compounds, such as cosmetics, fragrance products, cleaning agents and pesticides
• dry-cleaned clothing
• smoking
• mould growth in a damp environment
• poor housekeeping or inadequate cleaning
• poor ventilation resulting in accumulation of air pollutants

There are several kinds of air pollutants in offices and public places. The following are some common sources.

Chemical pollutants

• ozone from photocopiers and laser printers
• emissions from office equipment, wooden furniture, wall and floor coverings
• consumer products containing volatile organic compounds, such as cleaning agents and pesticides

Airborne particles

• particles of dust, dirt or other substances drawn into the building from outside
• activities in buildings, such as sanding wood, printing, copying, operating equipment, and smoking

Biological contaminants

• excessive level of bacteria, viruses and mould growth
• inadequate maintenance
• poor housekeeping and inadequate cleaning
• water problems, including water spills, leakages and condensation not promptly and properly fixed
• inadequate humidity control (relative humidity > 70%)
• brought into the building by occupants, infiltration or through the fresh air intake