Indoor mold:prevention and control

I. Prevention / II. Controlling/Mitigating Mold Growth

While respiratory protective equipment is available, the best way to avoid exposure to indoor molds is to prevent the growth of molds in the first place.

Controlling moisture is the key to preventing indoor mold growth. The relative humidity of indoor environments should be maintained at 20-40% in winter and no more than 60% the rest of the year. If and when moisture problems develop, rapid and appropriate responses are important to prevent mold spores from germinating (see sources and strategies below). If wetness or spills are dried within 24-48 hours, mold growth will not likely occur.

Indoor Sources

¸ Fix plumbing leaks, drips or “sweating” pipes.
¸ Limit sources of indoor humidity/dehumidify indoor air.
¸ Improve air movement in poorly ventilated areas.
¸ Increase fresh air ventilation when outdoor air is not humid.
¸ Warm cold surfaces where condensation occurs.

Outdoor Sources

¸ Maintain roof and gutter/downspout system.
¸ Direct runoff away from foundation by grading, draintile, landscaping, etc.
¸ Use air conditioning and keep building closed during high outdoor humidity.
¸ Prevent leakage around windows, doors, flashing, etc.
¸ Waterproof foundations

II. Controlling/Mitigating Mold Growth

Controlling mold exposure requires strategies that address removal of mold contaminants as well as the source of moisture that sustains the mold growth. The following steps should be taken to eliminate the presence of indoor molds.

(1) Identify moisture source and correct the problem (see lists of possible moisture sources and control above).
*Keep in mind that molds may be hidden. A moldy smell with or without visual confirmation is indicative of a mold problem, particularly if accompanied by health problems. Mold may be hidden on the back side of dry wall, wall paper or paneling, the top side of ceiling tiles, the underside of carpets or pads, etc. Investigation of hidden mold should be undertaken with caution as disturbing some sites with extensive mold growth may result in a massive release of spores (e.g. removal of wallpaper). Consider hiring an experienced professional if hidden mold is suspected.

Once the moisture problem has been addressed, which addresses the future growth of molds, removal of the existing mold contamination can begin. Molds can be toxic; personal protective equipment should be used to avoid excessive mold exposure during the clean-up process. The following personal protection products/procedures are recommended:

Respiratory protection (N-95 or TC-21C dust mask)
Goggles
Rubber gloves
Washable or disposable clothing
Ventilate area well when using bleach
Establish containment around the work area for large or heavily contaminated areas to minimize spread of spores

(2) Remove mold by cleaning and disposal
*Do not paint or caulk over mold. Paint applied over moldy surfaces is likely to peel.
a. Porous materials should be removed, bagged and discarded.
b. Non-porous materials may be cleaned with non-ammonia detergent and scrubbing.
c. Disinfect using _ - _ cup bleach per gallon of water.

(3) Dry thoroughly – keep in mind wet building materials take time to dry out completely. Fans and de-humidifiers may speed the process. The use of a moisture meter to monitor the moisture content of the material may be helpful. Moisture meters are available for purchase, but can cost up to $400. Some Minnesota Extension Service Offices loan out moisture meters – there is an office in every county: http://www.extension.umn.edu/offices/ .

Other sources of information:

EPA Website has two publications on indoor molds:
http://www.epa.gov/iaq/molds/index.html

A detailed protocol for mold mitigation and control at non-residential buildings can be found at the following link:
Department of Environmental Health and Safety, University of Minnesota http://www.epa.gov/iaq/molds/index.html

Sources:
http://www.health.state.mn.us
http://www.epa.gov/iaq/molds/index.html