There is no simple and cheap way to sample the air in your home to determine the level of all biological pollutants. Experts suggest that sampling for biological pollutants is not a useful problem-solving tool because it is almost impossible to know which biological pollutants cause various symptoms. Also, the amount of most biological substances required to cause disease is unknown and varies from one person to the next.

Does this make the problem sound hopeless? On the contrary, you can take several simple, practical actions to help remove sources of biological pollutants, to help get rid of pollutants, and to prevent their return.

Begin by touring your household. Follow your nose, and use your eyes. Check for musty odors, moisture on hard surfaces, and water stains. Be on the alert for two major factors which can create conditions in which biological pollutants will grow: nutrients and constant moisture with poor air circulation.

• Dust and construction materials, such as wood, wallboard, and insulation, contain nutrients that allow biological pollutants to grow.
• Firewood also is a source of moisture, fungi, and bugs.
• Appliances such as humidifiers, kerosene and gas heaters, and gas stoves add moisture to the air.

Some of the most common sources of biological pollutants in the home are:

• Dirty air conditioners
• Dirty humidifiers and/or dehumidifiers
• Bathroom without vents or windows
• Kitchen without vents or windows
• Dirty refrigerator drip pans
• Laundry room with unvented dryer
• Unventilated attic
• Carpet on damp basement floor
• Bedding
• Closet on outside wall
• Dirty heating/air conditioning system
• Dogs or cats
• Water damage around windows, the roof, or the basement

If you're thinking about moving, protect yourself by inspecting your potential new home:

• Have professionals check the heating and cooling system, including humidifiers and vents. Have duct lining and insulation checked for mold growth.
• Check for exhaust fans in bathrooms and kitchens. If there are no vents, do the kitchen and bathrooms have at least one window apiece? Does the cooktop have a hood vented outside? Does the clothes dryer vent outside? Are all vents to the outside of the building, not into attics or crawlspaces?
• Look for obvious mold growth throughout the house, including attics, basements, and crawlspaces, and around the foundation. See if there are many plants close to the house, particularly if they are damp and rotting. Downspouts from roof gutters should route water away from the building.
• Look for stains on the walls, floor or carpet (including any carpet over concrete floors) as evidence of previous flooding or moisture problems. Is there moisture on windows and surfaces? Any signs of leaks or seepage in the basement?
• Look for rotted building materials which may suggest moisture or water damage.
• If you or anyone else in the family has a pet allergy, ask if any pets have lived in the home.
• Examine the design of the building. Remember that in cold climates, overhanging areas, rooms over unheated garages, and closets on outside walls may be prone to problems with biological pollutants.
• Look for signs of cockroaches.

If you identify problems, have the landlord or seller correct them before you move in, or even consider moving elsewhere.