There are three major sources of contaminants affecting indoor air quality:

1. Indoor
   • Personal Activities (smoking or personal hygiene)
   • Housekeeping (deodorizers, cleaning materials, or dust)
   • Maintenance Activities (remodeling, new furniture/carpet, or pest control)
   • Miscellaneous: Emissions from office equipment (photocopier machines, VDTs)
     • Office supplies (toners, carbonless paper products)
     • Liquid spills or leaks
     • Room occupant load
     • Thermal and/or humidity comfort
2. Outdoor
   • Contaminated outdoor air (vehicle exhaust, pollen, or industrial pollutants)
   • Nearby source emissions (garbage dumpsters, loading docks, or re-entrained exhaust from buildings)
   • Soil gas (radon, underground storage tanks, or pesticides)
   • Microbial from standing water (molds or mildew)
3. HVAC System
   • Inadequate distribution of fresh air in ventilation system
   • Dust in ductwork
   • Dirty air filters
   • Microbiological growth in ductworks and/or humidifiers

Adapted from EPA "Building Air Quality, A Guide for Building Owners and Facility Managers", December 1991.

Industrial Hygiene | EH&S Fact Sheets