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This Guide provides information and guidance for homeowners and renters on how to clean up residential mold problems and how to prevent mold growth.
- Mold Basics
We would like to thank Paul Ellringer, PE, CIH, for providing the photo of mold on the back of wallpaper in the Hidden Mold section. Should you like to use some of the photos used in this guide, higher quality print versions are available in the Mold Gallery. These photos may be used for presentations and educational purposes without contacting EPA.
Please note that this document presents recommendations. EPA does not regulate mold or mold spores in indoor air. Find Frequently Asked Questions about mold and moisture.
- The key to mold control is moisture control .
- If mold is a problem in your home, you should clean up the mold promptly and fix the water problem.
- It is important to dry water-damaged areas and items within 24-48 hours to prevent mold growth.
Why is mold growing in my home?
Mold growing outdoors on firewood.
Molds come in many colors; both white and black molds are shown here. Click on the image for larger version.
Molds are part of the natural environment. Outdoors, molds play a part in nature by breaking down dead organic matter such as fallen leaves and dead trees, but indoors, mold growth should be avoided. Molds reproduce by means of tiny spores; the spores are invisible to the naked eye and float through outdoor and indoor air. Mold may begin growing indoors when mold spores land on surfaces that are wet. There are many types of mold, and none of them will grow without water or moisture.
Can mold cause health problems?
Molds are usually not a problem indoors, unless mold spores land on a wet or damp spot and begin growing. Molds have the potential to cause health problems. Molds produce allergens (substances that can cause allergic reactions), irritants, and in some cases, potentially toxic substances (mycotoxins). Inhaling or touching mold or mold spores may cause allergic reactions in sensitive individuals. Allergic responses include hay fever-type symptoms, such as sneezing, runny nose, red eyes, and skin rash (dermatitis). Allergic reactions to mold are common. They can be immediate or delayed. Molds can also cause asthma attacks in people with asthma who are allergic to mold. In addition, mold exposure can irritate the eyes, skin, nose, throat, and lungs of both mold-allergic and non-allergic people. Symptoms other than the allergic and irritant types are not commonly reported as a result of inhaling mold. Research on mold and health effects is ongoing.
Magnified mold spores
Molds gradually destroy the things they grow on. You can prevent damage to your home and furnishings, save money, and avoid potential health problems by controlling moisture and eliminating mold growth
This [guidance] provides a brief overview; it does not describe all potential health effects related to mold exposure. For more detailed information consult a health professional. You may also wish to consult your state or local health department.
It is impossible to get rid of all mold and mold spores indoors; some mold spores will be found floating through the air and in house dust. The mold spores will not grow if moisture is not present. Indoor mold growth can and should be prevented or controlled by controlling moisture indoors. If there is mold growth in your home, you must clean up the mold and fix the water problem. If you clean up the mold, but don't fix the water problem, then, most likely, the mold problem will come back.
Who should do the cleanup depends on a number of factors. One consideration is the size of the mold problem. If the moldy area is less than about 10 square feet (less than roughly a 3 ft. by 3 ft. patch), in most cases, you can handle the job yourself, follow the guidelines. However:
If you already have a mold problem - ACT QUICKLY. Mold damages what it grows on. The longer it grows, the more damage it can cause.
Leaky window - mold is beginning to rot the wooden frame and windowsill.
- If there has been a lot of water damage, and/or mold growth covers more than 10 square feet, consult EPA's Mold Remediation in Schools and Commercial Buildings . Although focused on schools and commercial buildings, this document is applicable to other building types.
Mold Cleanup Guidelines
Tips and techniques
The tips and techniques presented in this section will help you clean up your mold problem. Professional cleaners or remediators may use methods not covered in this publication. Please note that mold may cause staining and cosmetic damage. It may not be possible to clean an item so that its original appearance is restored.
Mold growing on the underside of a plastic lawn chair in an area where rainwater drips through and deposits organic material. Click on the image for a larger version.
Mold growing on a piece of ceiling tile. Click on the image for a larger version.
- Fix plumbing leaks and other water problems as soon as possible. Dry all items completely.
rug cleaning, water damage, and fire or water restoration are commonly listed in phone books. Be sure to ask for and check references. Look for specialists who are affiliated with professional organizations.
Places that are often or always damp can be hard to maintain completely free of mold. If there's some mold in the shower or elsewhere in the bathroom that seems to reappear, increasing ventilation (running a fan or opening a window) and cleaning more frequently will usually prevent mold from recurring, or at least keep the mold to a minimum
What to Wear When Cleaning Moldy Areas
It is important to take precautions to LIMIT YOUR EXPOSURE to mold and mold spores.
Cleaning while wearing N-95 respirator, gloves and goggles. Click on the image for a larger version.
- Avoid breathing in mold or mold spores. In order to limit your exposure to airborne mold, you may want to wear an N-95 respirator, available at many hardware stores and from companies that advertise on the Internet. (They cost about $12 to $25.) Some N-95 respirators resemble a paper dust mask with a nozzle on the front, others are made primarily of plastic or rubber and have removable cartridges that trap most of the mold spores from entering. In order to be effective, the respirator or mask must fit properly, so carefully follow the instructions supplied with the respirator. Please note that the Occupational Safety and Health Administration (OSHA) requires that respirators fit properly (fit testing) when used in an occupational setting; consult OSHA for more information (800-321-OSHA or www.osha.gov ).
How Do I Know When the Remediation or Cleanup is Finished?
Mold growing on a suitcase stored in a humid basement. Click on the image for a larger version.
You must have completely fixed the water or moisture problem before the cleanup or remediation can be considered finished.
- You should have completed mold removal. Visible mold and moldy odors should not be present. Please note that mold may cause staining and cosmetic damage.
Moisture and Mold Prevention and Control Tips
Moisture Control is the Key to Mold Control
Mold growing on the surface of a unit ventilator. Click on the image for a larger version.
Condensation on the inside of a windowpane.
- When water leaks or spills occur indoors - ACT QUICKLY. If wet or damp materials or areas are dried 24-48 hours after a leak or spill happens, in most cases mold will not grow.
Actions that will help to reduce humidity
- Vent appliances that produce moisture, such as clothes dryers, stoves, and kerosene heaters to the outside where possible. (Combustion appliances such as stoves and kerosene heaters produce water vapor and will increase the humidity unless vented to the outside.)
Actions that will help prevent condensation
Mold growing on a wooden headboard in a room with high humidity. Click on the image for a larger version.
Suspicion of hidden mold
Mold growing on the back side of wallpaper.
Water stain on a basement wall -- locate and fix the source of the water promptly. Click on the image for a larger version.
You may suspect hidden mold if a building smells moldy, but you cannot see the source, or if you know there has been water damage and residents are reporting health problems. Mold may be hidden in places such as the back side of dry wall, wallpaper, or paneling, the top side of ceiling tiles, the underside of carpets and pads, etc. Other possible locations of hidden mold include areas inside walls around pipes (with leaking or condensing pipes), the surface of walls behind furniture (where condensation forms), inside ductwork, and in roof materials above ceiling tiles (due to roof leaks or insufficient insulation).
Investigating hidden mold problems
Investigating hidden mold problems may be difficult and will require caution when the investigation involves disturbing potential sites of mold growth. For example, removal of wallpaper can lead to a massive release of spores if there is mold growing on the underside of the paper. If you believe that you may have a hidden mold problem, consider hiring an experienced professional.
Cleanup and Biocides
Biocides are substances that can destroy living organisms. The use of a chemical or biocide that kills organisms such as mold (chlorine bleach, for example) is not recommended as a routine practice during mold cleanup. There may be instances, however, when professional judgment may indicate its use (for example, when immune-compromised individuals are present). In most cases, it is not possible or desirable to sterilize an area; a background level of mold spores will remain - these spores will not grow if the moisture problem has been resolved. If you choose to use disinfectants or biocides, always ventilate the area and exhaust the air to the outdoors. Never mix chlorine bleach solution with other cleaning solutions or detergents that contain ammonia because toxic fumes could be produced.
Please note: Dead mold may still cause allergic reactions in some people, so it is not enough to simply kill the mold, it must also be removed.