IAQ Contaminant Sources

Indoor air contaminants can originate within the building or be drawn in from outdoors. If contaminant sources are not controlled, IAQ problems can arise, even if the HVAC system is properly designed and well maintained. It may be helpful to think of indoor air pollutant sources as fitting into one of the following categories. The examples given for each category are not intended to be a complete list.

Air Quality Sources Outside the Building

Contaminated Outside Air

  • pollen, dust, fungal spores
  • industrial pollutants
  • general vehicle exhaust

Emissions From Nearby Sources

  • exhaust from vehicles on nearby roads or in parking lots or garages
  • loading docks
  • odors from dumpsters
  • re-entrained (drawn back into the building) exhaust from the building
  • unsanitary debris near the outdoor air intake

Soil Gas

  • radon
  • leakage from underground fuel tanks
  • contaminants from previous uses of the site (e.g., landfills)
  • pesticides

Moisture or Standing Water Promoting Excess Microbial Growth

  • rooftops after rainfall
  • crawlspace


HVAC System

  • dust or dirt in ductwork or other components
  • microbiological growth in drip pans, humidifiers, ductwork, coils
  • improper use of biocides, sealants, and/or cleaning compounds
  • improper venting of combustion products
  • refrigerant leakage

Non-HVAC Equipment

  • emissions from office equipment (volatile organic compounds, ozone)
  • supplies (solvents, toners, ammonia)
  • emissions from shops, labs, cleaning processes
  • elevator motors or other mechanical systems

Human Activities

Personal Activities

  • smoking
  • cooking
  • body odor
  • cosmetic odors

Housekeeping Activities

  • cleaning materials and procedures
  • emissions from stored supplies or trash
  • use of deodorizers and fragrances
  • airborne dust or dirt (e.g., circulated by sweeping and vacuuming)

Maintenance Activities

  • microorganisms in mist from improperly maintained cooling towers
  • airborne dust or dirt
  • volatile organic compounds from paint, adhesives, or other products
  • pesticides from pest control activities
  • emissions from stored supplies

Building Components and Furnishings

Locations That Produce or Collect Dust or Fibers

  • textured surfaces such as carpeting, curtains, or other textiles
  • open shelving
  • old or deteriorated furnishings
  • materials containing damaged asbestos
  • Unsanitary Conditions and Water Damage
  • microbiological growth on or in soiled or water damaged furnishings
  • microbiological growth in areas of surface condensation
  • standing water from clogged or poorly designed drains
  • dry traps that allow the passage of sewer gas

Chemicals Released from Building Components or Furnishings

  • volatile organic compounds or
  • inorganic compounds

Other Sources

Accidental Events

  • spills of water or other liquids
  • microbiological growth due to flooding or to leaks from roofs or piping
  • fire damage (soot, PCBs from electrical equipment, odors)

Special Use Areas and Mixed Use Buildings

  • smoking lounges
  • laboratories
  • print shops, art rooms
  • exercise rooms
  • beauty salons
  • food preparation areas

Redecorating or Remodeling and Repair Activities

  • emissions from new furnishings
  • dust and fibers from demolition
  • odors and volatile organic and inorganic compounds from paint, caulk, adhesives
  • microbiologicals released from demolition or remodeling activities