Moisture and mold

Mold starts with moisture. It may begin growing indoors when mold spores land on wet surfaces, and no type of mold will grow without water or moisture. High humidity keeps the air moist and makes mold more likely. If indoor air is too humid, moisture can condense on surfaces and help mold grow.

Mold can affect health. Exposure to damp and moldy places may cause a variety of health effects, or none at all. For some people, mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes or a skin rash. It can also lead to allergic reactions, asthma and other breathing problems.

Source: U.S. EPA · CDC

Cooling is where most system moisture comes from. Cooling coils are designed to remove water from the air and can be a major source of moisture in the system that can lead to mold, so make sure the condensate pan drains properly. Drain pans can become a home for mold and bacteria if they are not installed and maintained properly. If the pans do not drain or are not cleaned often, water can get into the system and contaminate the ducts.

Other parts need care too. Furnace humidifiers must be cleaned regularly to prevent mold and bacteria. In ductless mini-splits, dust and moisture can build up and lead to fungal growth, which is more common in high wall-mounted units than in ceiling or floor units. Mold growing near the intake of a heating and cooling system points to possible humidity problems.

Once it is in the system, it can travel. The heating and cooling system has the potential to spread mold throughout a building. Portable air cleaners and furnace filters do not address the cause of mold and musty odors. That is why the fix starts with the water, not the filter.

Source: U.S. EPA · U.S. Department of Energy

Below-ground spaces are a common source. Places that are always or often damp, such as bathrooms, laundry and utility rooms and basements, are common spots for mold in homes. Water can enter your home by leaking in from outside or seeping through basement floors. Water seeping into crawl spaces or basements should be stopped quickly, and steps such as a sump pump or regrading around the building can prevent future leaks.

Ducts that run through these spaces need protection. Make sure ducts are properly sealed and insulated in spaces that are not cooled, such as attics and crawl spaces, to keep condensation out of the system. Rust on a drain pipe shows that condensation forms on it, and the pipe should be insulated. A white, fibrous material on crawl space soil may be salts rather than mold, but it shows moisture has been a problem and the area should be looked at more closely.

Source: U.S. EPA

A few numbers do most of the work. The EPA says to keep indoor humidity below 60 percent if possible, ideally between 30 and 50 percent. Humidifiers should be set below 60 percent, because higher humidity is likely to cause condensation that can lead to mold. A moisture or humidity gauge, sold at most hardware stores, shows whether your home is at a good level.

Speed matters after a leak. Dry water-damaged areas and items within 24 to 48 hours to prevent mold growth. If you see condensation on windows, walls or pipes, act quickly to dry the surface and reduce the source of moisture. Use air conditioners or dehumidifiers when needed, and vent appliances that make moisture, such as clothes dryers, to the outside where possible.

Source: U.S. EPA

Small areas can often be handled at home. If the moldy area is less than about 10 square feet, in most cases you can handle the job yourself by following the EPA's guidelines. Scrub mold off hard surfaces with detergent and water and dry them completely. Using bleach or another chemical that kills mold is not recommended as a routine part of cleanup. Do not paint or caulk over mold; clean it and dry the surface first.

Some materials cannot be saved. Porous materials such as ceiling tiles and carpet may have to be thrown away if they become moldy. Duct insulation or any other insulation that is wet or visibly moldy should be removed and replaced by a qualified heating and cooling contractor.

Your system needs special care. Do not run the heating and cooling system if you know or suspect it has mold in it, because it could spread mold through the building. Disturbing hidden mold can spread it, and opening and closing air handlers can send high levels of dust and mold into the air. If you can see or smell mold, testing is usually not needed; there is likely a moisture source to repair. Cleanup is not finished until the water or moisture problem is completely fixed.

Source: U.S. EPA · Illinois Department of Public Health

Bigger jobs call for help. The Illinois Department of Public Health says a professional mold remediator should clean up mold larger than 10 square feet. If the damage came from sewage or other contaminated water, call in a professional with experience cleaning buildings damaged by contaminated water. If you think you may have a hidden mold problem, consider hiring an experienced professional.

Choosing someone takes a little care. The EPA has no certification program for mold inspectors or remediation firms and keeps no list of them, though some states might. If you hire a contractor for cleanup, make sure they have experience cleaning up mold. The state health department does not license people to do mold assessments or testing and cannot recommend any contractor.

Illinois has a mold remediation registration law. The Mold Remediation Registration Act requires the state health department to set rules for mold remediation businesses to register with the state and show active third-party certification and financial responsibility. Until those rules are adopted, mold remediation professionals do not have to register. The rules can change, so check the state's current requirements before you hire.

Source: Illinois Department of Public Health · U.S. EPA