Mold Control Starts With Moisture, Dry Leaks in 24-48 Hours
The U.S. Environmental Protection Agency (EPA) says the key to mold control is moisture control; after a leak or spill, water-damaged areas and items should be dried within 24 to 48 hours to prevent mold growth. If mold is already growing 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, the mold will most likely come back.
EPA says molds have the potential to cause health problems; inhaling or touching mold or mold spores may cause allergic reactions in sensitive individuals. This article follows EPA's mold guide for homeowners and renters: how to clean up, what to wear, how to prevent mold, and what renters should do. EPA also says that if you have health concerns, you should consult a health professional before starting cleanup. Everyone's health is different; if you have questions, ask your health care provider.
Who should clean up
EPA explains (EPA, Mold, Moisture and Your Home):
- Under 10 square feet: If the moldy area is less than about 10 square feet (roughly a 3 ft. by 3 ft. patch), in most cases you can handle the job yourself.
- Large areas or heavy water damage: If there has been a lot of water damage, or the mold covers more than 10 square feet, consult EPA's mold remediation guide for schools and commercial buildings.
- Hiring someone: If you hire a contractor, make sure they have experience cleaning up mold, check references, and ask them to follow EPA's mold remediation guidance or other guidelines from professional or government organizations.
- Caused by sewage: If the water or mold damage was caused by sewage or other contaminated water, call in a professional who has experience with this kind of damage.
- Heating and cooling system: If you suspect the heating and air conditioning system has mold, do not run it if you know or suspect it is contaminated; it could spread mold throughout the building.
- Health concerns: If you have health concerns, consult a health professional before starting cleanup.
How to clean up
- Fix the leak first: Fix plumbing leaks and other water problems as soon as possible, and dry all items completely.
- Hard surfaces: Scrub mold off with detergent and water, then dry completely.
- Absorbent materials: Absorbent materials such as ceiling tiles and carpet may have to be thrown away if they become moldy.
- Don't paint over it: Do not paint or caulk moldy surfaces; clean up the mold and dry the surface before painting, because paint applied over mold is likely to peel.
- Bleach: Using a biocide such as chlorine bleach is not recommended as a routine practice during mold cleanup; if you use one, always ventilate and exhaust the air to the outdoors; never mix bleach with cleaners that contain ammonia, because toxic fumes could be produced.
- Dead mold: Dead mold may still cause allergic reactions in some people, so killing it is not enough; it must be removed.
- Bathrooms: In places that are often damp, like bathrooms, increasing ventilation (running a fan or opening a window) and cleaning more often will usually keep mold from coming back.
What to wear
- N-95 respirator: To avoid breathing in mold or spores, you may want to wear an N-95 respirator; it must fit properly to be effective.
- Gloves: Long gloves that extend to the middle of the forearm are recommended; ordinary household rubber gloves may be used with water and a mild detergent; avoid touching mold with bare hands.
- Goggles: Goggles without ventilation holes are recommended.
How to prevent mold
- Act fast on leaks: If a leak or spill is dried within 24 to 48 hours, in most cases mold will not grow.
- Indoor humidity: If possible, keep indoor relative humidity below 60%, ideally between 30% and 50%.
- Venting moisture: Run the bathroom fan or open a window when showering; use exhaust fans or open windows when cooking or running the dishwasher; use air conditioners or dehumidifiers when needed.
- Condensation: If you see condensation on windows, walls or pipes, dry the surface quickly and reduce the moisture source.
- Outside the house: Clean and repair roof gutters regularly; make sure the ground slopes away from the foundation so water does not collect around it; keep air conditioning drip pans clean and drain lines flowing.
Renters
- Report it right away: Report all plumbing leaks and moisture problems immediately to your building owner, manager or superintendent.
- If it keeps going unfixed: If persistent water problems are not addressed, you may want to contact local, state or federal health or housing authorities; you can also contact your state health department.
For hurricane and flood preparation, see Hurricanes, Know Your Evacuation Zone, Never Drive in Floods; for what to watch for when cleaning up after a tornado, see Tornado? Get to a Safe Room, or the Lowest Windowless Room.
What this article did not check
- Testing for mold: EPA says that in most cases, if mold is visible, sampling is unnecessary; this article did not look into how sampling is done.
- Landlord legal duties: EPA says it does not regulate mold in indoor air and that the page is a set of recommendations; this article did not check state rules for landlords.
- Health effects of mold: The page is a brief overview and does not list all health effects, so this article does not cover them.
FAQ
Mold in the bathroom keeps coming back. What can I do?
EPA says increasing ventilation (running a fan or opening a window) and cleaning more often will usually keep mold from recurring, or at least keep it to a minimum.
Can I use bleach to clean mold?
EPA says using a biocide such as chlorine bleach is not recommended as a routine practice; if you use one, always ventilate and exhaust the air to the outdoors, and never mix it with cleaners that contain ammonia.
Can I just paint over a moldy wall?
No. EPA says to clean up the mold and dry the surface before painting; paint applied over mold is likely to peel.
I reported a leak and nothing has been done. What now?
EPA says to report leaks and moisture problems immediately to your building owner, manager or superintendent; if the problem is not addressed, you may want to contact local, state or federal health or housing authorities.
Sources and date checked
All checked on 2026-11-02.
- U.S. EPA, A Brief Guide to Mold, Moisture and Your Home (page updated 2026-02-18):https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home