Why is mold growing in my home?
Can mold cause health problems?
How do I get rid of mold?
• 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.
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.
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. This brochure 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.
if you suspect that the heating/ventilation/air conditioning (HVAC) system may be contaminated with mold (it is part of an identified moisture problem, for instance, or there is mold near the intake to the system), consult EPA’s guide Should You Have the Air Ducts in Your Home Cleaned? before taking further action. Do not run the HVAC system if you know or suspect that it is contaminated with mold – it could spread mold throughout the building.
Visit: EPA Publications, or call: (800) 438-4318 for a free copy.
If the water and/or mold damage was caused by sewage or other contaminated water, then call in a professional who has experience cleaning and fixing buildings damaged by contaminated water.
If you have health concerns, consult a health professional before starting cleanup.
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, following the guidelines below.
If there has been a lot of water damage, and/or mold growth covers more than 10 square feet, consult the U.S. Environmental Protection Agency (EPA) guide: Mold Remediation in Schools and Commercial Buildings. Although focused on schools and commercial buildings, this document is applicable to other building types. It is available free by calling the EPA Indoor Air Quality Information Clearinghouse at
Visit: EPA Publications, or call: (800) 438-4318 for a free copy.
If you choose to hire a contractor (or other professional service provider) to do the cleanup, make sure the contractor has experience cleaning up mold. Check references and ask the contractor to follow the recommendations in EPA’s Mold Remediation in Schools and Commercial Buildings, the guidelines of the American Conference of Governmental Industrial Hygenists (ACGIH), or other guidelines from professional or government organizations.
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.Fix plumbing leaks and other water problems as soon as possible.
Dry all items completely.Scrub mold off hard surfaces with detergent and water, and dry completely.Absorbent or porous materials, such as ceiling tiles and carpet, may have to be thrown away if they become moldy. Mold can grow on or fill in the empty spaces and crevices of porous materials, so the mold may be difficult or impossible to remove completely.Avoid exposing yourself or others to mold (see discussions: What to Wear When Cleaning Moldy Areas and Hidden Mold). Do not paint or caulk moldy surfaces. Clean up the mold and dry the surfaces before painting. Paint applied over moldy surfaces is likely to peel.If you are unsure about how to clean an item, or if the item is expensive or of sentimental value, you may wish to consult a specialist. Specialists in furniture repair, restoration, painting, art restoration and conservation, carpet and 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.
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 osha.gov/ ).
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 damageYou should have revisited the site(s) shortly after cleanup and it should show no signs of water damage or mold growth.
Moisture control is the key to mold control, so 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.Clean and repair roof gutters regularly.Make sure the ground slopes away from the building foundation, so that water does not enter or collect around the foundation.Keep air conditioning drip pans clean and the drain lines unobstructed and flowing properly.Keep indoor humidity low. If possible, keep indoor humidity below 60 percent (ideally between 30 and 50 percent) relative humidity. Relative humidity can be measured with a moisture or humidity meter, a small, inexpensive ($10-$50) instrument available at many hardware stores.If you see condensation or moisture collecting on windows, walls or pipes ACT QUICKLY to dry the wet surface and reduce the moisture/water source. Condensation can be a sign of high 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.) Use air conditioners and/or de-humidifiers when needed.Run the bathroom fan or open the window when showering. Use exhaust fans or open windows whenever cooking, running the dishwasher or dishwashing, etc.
Reduce the humidity (see above). Increase ventilation or air movement by opening doors and/or windows, when practical. Use fans as needed. Cover cold surfaces, such as cold water pipes, with insulation.Increase air temperature.
In most cases, if visible mold growth is present, sampling is unnecessary. Since no EPA or other federal limits have been set for mold or mold spores, sampling cannot be used to check a building’s compliance with federal mold standards. Surface sampling may be useful to determine if an area has been adequately cleaned or remediated. Sampling for mold should be conducted by professionals who have specific experience in designing mold sampling protocols, sampling methods, and interpreting results. Sample analysis should follow analytical methods recommended by the American Industrial Hygiene Association (AIHA), the American Conference of Government.
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 problemsInvestigating 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.
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.
For more information on mold related issues including mold cleanup and moisture control/condensation/humidity issues, you can call:
EPA Indoor Air Quality Information Clearinghouse at (800) 438-4318
EPA’s Mold Resources page EPA.GOV
The EPA publication Mold Remediation in Schools and Commercial Buildings (EPA 402-K-01-001, March 2001), is available.
Other Indoor Air Quality Publications located here: Formatted Version
EPA would like to thank Paul Ellringer, PE, CIH, for providing the photo of mold on the back of wallpaper in the Hidden Mold section.
• How do I know if I have a mold problem?
• Could my a/c and heating system be part of the problem?
• Who can test for mold and other Indoor Air Quality problems?
The Facts About Mold and Your Home
Mold spores are literally as old as dirt. Check out Leviticus Chapter 14 (written over 3000 years ago) for mold remediation instructions. In recent years more people have become sensitive to mold. To some mold can be toxic. Yet some people aren’t sensitive to mold at all. Today’s homes are better insulated and tighter. There’s more potential to trap the moisture that can promote biological growth.
At what point can mold become a threat? Mold has been called ‘Mother Nature’s reclaiming process.” Mold spores are literally everywhere. A typical healthy house is host to tens of thousands of mold spores. The problem begins when mold spores find an environment where they can reproduce exponentially. Mold needs moisture to grow. Control the moisture and you can control mold growth. If good housekeeping keeps it in check, the problem is often easily cleaned up.What if there appears to be mold in my air conditioning system? It’s your air conditioning system’s job to ventilate your home. The ducts are designed to supply and return airflow to each room. If there is a mold infestation on your home, an increased amount of mold spores become present. As the air conditioning system constantly recycles air throughout your home, it becomes infected by the active mold culture and often is first noticed on the registers. In rare cases mold can be caused by the air conditioning system due to lack of maintenance, clogged or leaking drain pans, etc. These HVAC-related causes can usually be corrected by a qualified heating and air conditioning contractor.Can my air conditioning system cause mold? A properly designed, installed, and maintained air conditioning system should not cause mold. However, while an oversized or improperly designed system may somewhat cool your home, it may not remove enough moisture. Too much moisture in your home’s air can increase the potential for mold growth. Improper installation, lack of maintenance, and water drainage issues can also lead to biological growth.
QUESTION: Can mold cause health problems?
ANSWER: Many people are unaffected by mold growth. Other people can become ill when exposed to high levels of mold. Consult your physician if you suspect an intolerance to mold.
QUESTION: How can I tell if mold in my house is the bad kind?
ANSWER: It takes a laboratory and a 600X microscope to identify a mold species. Your doctor can run a series of tests to determine your reactions to various molds. Mold identification is usually outside the expertise of your air conditioning contractor and should be performed by a qualified specialist.
QUESTION: What causes mold spores to grow?
ANSWER: Mold spores are everywhere. They feed on just about anything organic that can rot. But they exist in a dormant state until one missing ingredient is added: Moisture. At 70% relative humidity, it takes 100 days to establish a culture. At 90% humidity mold can establish a culture in 3 days. Moisture is at the root of all mold problems.
QUESTION: What can I do to control mold?
ANSWER: Typical household cleaning contains mold growth in visible areas and normal household cleaning products can clean susceptible surfaces including the shower and tub areas, or around sinks. Use exhaust fans after showering. Repair any plumbing or roof leaks. Always clean up spills or flooding immediately and control moisture in basements.
QUESTION: What should I expect from my heating/cooling contractor?
ANSWER: A well trained air conditioning and heating contractor is your Indoor Air Quality specialist when addressing heating, cooling, basic filtration and ventilating your home. But when it comes to air particle testing, taking mold samples, biological identification, mold remediation, or health issues, you should look to a specialist for help. These tests are outside the licensing and training of a typical air conditioning contractor.
QUESTION: Who should I contact if I have a serious mold issue?
ANSWER: There are a number of organizations you can contact to be put in touch with a mold testing or remediation specialist. You can start by contacting one of the following organizations or visiting their web sites:
International Association of Mold Remediation Specialists:
P.O. Box 273, 4750 Bryant Irvin Road Fort Worth, TX 76132 (817) 735-1900
Indoor Air Quality Association:
12339 Carroll Avenue Rockville, MD 20852 Phone: (301) 231-8388
American Industrial Hygiene Association:
2700 Prosperity Ave., Suite 250 Fairfax, VA 22031 (703) 849-8888