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About Moisture and Mold

There are more than 100,000 species of mold. At least 1,000 species of mold are common in the U.S. Molds can be found almost anywhere and they can have harmful health implications and destroy the structure of a home. Mold can grow on virtually any substance when moisture is present, including wood, paper, carpet, and foods. Moisture can come from many sources, such as showers or even cooking can add moisture to the air in your home. Outdoors, many molds live in the soil and play a key role in the breakdown of leaves, wood, and other plant debris. When excessive moisture or water accumulates indoors, mold growth will often occur, particularly if the moisture problem remains undiscovered or unmitigated. There is no practical way to eliminate all molds and mold spores in the indoor environment.

Tips to eliminating molding in your home:

  • Wash mold off of hard surfaces and dry completely. Absorbent materials, such as ceiling, tiles and carpet, may have to be replaced if they are contaminated with mold.
  • Use dehumidifiers and air conditioners, especially in hot, humid climates, to reduce moisture in the air; however be sure that the appliances themselves don't become sources of biological pollutants. Use exhaust fans or open windows in kitchens and bathrooms when showering, cooking, or using the dishwasher.
  • Maintain low indoor humidity, ideally between 30-50% relative humidity. Humidity levels can be measured by hygrometers, which are available at local hardware stores.
  • Fix leaks and seepage. If water is entering the house from the outside, your options range from simple landscaping to extensive excavation and waterproofing, thereby ensuring that the ground slope's away from the house. Water in the basement can result from the lack of gutters or a water flow toward the house.
  • Put a plastic cover over dirt in crawlspaces to prevent moisture from coming in from the ground. Crawlspaces need to be well ventilated.
  • Utilize exhaust fans in bathrooms and kitchens to remove moisture to the outside (not into the attic). Vent your clothes dryer to the outside.
  • Turn off certain appliances (such as humidifiers or kerosene heaters) if you notice moisture on windows and other surfaces.
  • Raise the temperature of cold surfaces where moisture condenses by installing storm windows (a storm window installed on the inside works better than one installed on the outside).
  • Open doors between rooms (especially doors to closets which may be colder than the rooms) to increase circulation. Increase air circulation by using fans and by moving furniture from wall corners to promote air and heat circulation.
  • Carpet can absorb moisture and serve as a place for biological pollutants to grow. Use area rugs, which can be taken up and washed often. In certain climates, if carpet is to be installed over a concrete floor, it may be necessary to use a vapor barrier (plastic sheeting) over the concrete and cover that with sub-flooring (insulation covered with plywood) to prevent a moisture problem.
  • Many of the sections of your heating and cooling systems may not be accessible for visible inspection, so ask your service provider to you show you any mold they noticed.
  • When you have insulated air ducts and the insulation gets wet or moldy, it cannot be effectively cleaned and should be removed and replaced.

For more information on mold and moisture, visit the following web sites:

U.S. Department of Housing and Urban Development's Office of Healthy Homes and Lead Hazard Control Mold in Residential Buildings

Centers for Disease Control and Prevention (CDC)

EPA Indoor Air Quality

EPA info on Biological Contaminants

EPA Mold Remediation in Schools and Commercial Buildings

EPA Mold Resources

University of California Indoor Air Quality Tools

University of Minnesota Environmental Health and Safety Program - Indoor Air Quality

University of Tulsa Indoor Air Program

New York City Department of Health Guidelines on Assessment and Remediation of Fungi in Indoor Environments

Healthy House Institute

Health House

American Lung Association

Energy and Environmental Building Association

National Safety Council Indoor Air Program

U.S. Department of Agriculture's Demonstration House

Health Canada, Health Protection Branch, Laboratory Centre for Disease Control, Office of Biosafety

Institute of Inspection, Cleaning and Restoration Certification

Content updated on 5/25/2007

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