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Extension > Environment > Housing Technology > Moisture management > Molds – your safe home

Molds – your safe home

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Wanda Olson and McGregor Pearce
Reviewed 2011

What are molds?

Molds are microorganisms. They are found everywhere. They can grow on almost anything if it is moist enough. Inside your home molds grow quickly on damp surfaces like bathroom walls and trim around windows. Molds may look like furry growth, black stains, or specks of black, white, orange, green, or brown.

What do molds do to our body?

When a growth of mold appears, it can send clouds of invisible bits of mold through the air. These bits of mold can cause infections, allergies, asthma, and other breathing problems. To avoid these health problems, keep your home as mold-free as possible.

How does mold get into our homes?

The more people who live in a home, the more likely it is that molds will grow inside it. This is because we release a lot of moisture in the air when we breathe. When we take long hot showers, cook with uncovered pots, dry clothes on an indoor clothesline, or use humidifiers, we also make more moisture for molds to grow. Storing wet firewood, watering many plants, and storing many vegetables like potatoes and squash can make a mold problem more likely, too.

How can I tell if I have a mold problem?

Any part of your home that gets wet is likely to be moldy. Check:

How to I get rid of a mold problem?

Clean surfaces

Scrub all moldy surfaces using a stiff brush, hot water and a soap or detergent that does NOT contain ammonia. Collect used liquid with a wet/dry vacuum, mop or sponge. Rinse area clean with clean water and dry thoroughly. Use protective equipment when working around mold. The following equipment can help minimize exposure to mold:

Disinfect surfaces

After cleaning the affected area as described above, wipe down the wall, ceiling, or floor again using a mixture of liquid household chlorine bleach and water. If you are cleaning a small area, use 5 cups of water mixed with 1/2 cup bleach. If you are cleaning a large area, use a 5-gallon pail of water and add 1/2 gallon of bleach to it. Be sure to follow all the directions and warnings on the bleach label. Never mix bleach with ammonia; toxic fumes will be produced. Be sure to open windows when you use bleach, so you have fresh air to breathe and the bleach does not irritate your lungs. Always handle bleach with caution.

Ideally, surfaces should be allowed to air dry to maximize their contact time with the bleach.

Throw what can not be cleaned—when molds get inside materials like carpets and mattresses, they cannot be cleaned. Throw them away. But you can get rid of molds in bedding, curtains, drapes and clothes by washing or dry cleaning them. Some non-porous materials can be cleaned.

How to I keep mold from growing in my home?

Theresa Bauer, University of Minnesota Department of Design, Housing, and Apparel

Moisture from room air condenses on the coil and drips into the water bucket or through a hose into a nearby drain.

bath-fans-kitchen-fans-and-clothes-dryer-fans-vent-moist-air-to-the-outside-of-the-home-window-fans-will-also-move-moist-air-out-of-the-home

Theresa Bauer, University of Minnesota Department of Design, Housing, and Apparel

Bath fans, kitchen fans and clothes dryer fans vent moist air to the outside of the home. Window fans will also move moist air out of the home.

Keep your home as dry as possible. Repair roof and plumbing leaks right away. Make sure that the ground around the foundation of your house slopes away from the house, so that your basement is less likely to flood.

If your home has kitchen, bathroom, or window fans that vent (send) the moist air outside, use them when you cook or take a shower. If you do not have fans, open a window when you cook or shower, cover pots when cooking, and try to take cool, short showers. Dry clothing on a clothesline outside or use a clothes dryer that vents (sends) air outdoors.

If your basement is damp, get a dehumidifier (not a humidifier, which adds air moisture) to remove moisture from the air. If you have an air conditioner to run in the summer, it will remove some moisture as it cools the air. When you use an air conditioner or dehumidifier, don't keep your windows open if it is damp outside.

Do not finish the walls of your basement with insulation and wallboard unless your basement is very dry. Also avoid putting wall-to-wall carpet on your basement floor. If your basement floor is concrete, you can paint it and use area rugs instead. Then you can take the rugs outside to clean and dry them, and the rugs aren't as likely to get moldy.

Where can I get more information?

For more information (in English) on mold go to the Minnesota Department of Health website.

In the Twin Cities, call (651) 201-4601. Outside the Twin Cities, call 1-800-798-9050.

Information about mold, moisture, and indoor air quality is available on the U.S. Environmental Protection Agency website.

The Energy Information Center has information on preventing damp basements, moisture and housing concerns. In the Twin Cities, call (651) 296-5175. Outside the Twin Cities, call 1-800-657-3710.


Reviewed by Dick Stone, April 2011

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