Your place · Cleaning and laundry

Mold and moisture: what to watch for

Mold grows wherever things stay wet. Dry leaks and spills within 24 to 48 hours, keep humidity below 60 percent, and fix the water problem, or the mold comes back. You can usually clean a patch under about 10 square feet yourself with detergent, water, gloves and goggles. Anything bigger, anything after sewage or a flood, and every leak in a rental goes to your landlord, in writing.

Easy30 min for a small cleanup$Checked October 2, 2026

You'll need

Detergent and water, and a scrub brush
Long rubber or nitrile gloves, and goggles without vent holes
An N-95 respirator (about $12–$25), for anything more than a tiny spot
A humidity meter ($10–$50 at hardware stores), if you want to measure
Your phone, to photograph the damage before you clean

What to know

Look and sniff. Mold can be spots of many colors, and it can smell musty. If you see or smell it, remove it. Source: CDC²
Think water first. If mold is a problem, you have to clean it up and get rid of the moisture source. Source: EPA³ Mold grows around leaks in roofs, windows and pipes, and where there's been flooding. Source: CDC² Condensation on windows, walls or pipes is a sign of high humidity. Source: EPA¹
Renting? Report every plumbing leak and moisture problem to your landlord or building manager right away. Source: EPA¹ Take photos first, and put the report in writing so there's a record.
Size it up. If the moldy area is under about 10 square feet, roughly a 3-by-3-foot patch, you can usually clean it yourself. Bigger than that, a lot of water damage, or water from sewage calls for a professional. Source: EPA¹
Suit up: long gloves to mid-forearm, goggles without vent holes and, to limit what you breathe in, an N-95 respirator that fits properly. Source: EPA¹
Scrub hard surfaces with detergent and water, then dry them completely. Source: EPA¹
Throw out what you can't clean. Porous things like ceiling tiles and carpet may have to go, because mold fills their tiny spaces and can be impossible to remove completely. Source: EPA¹
Check your work. You're done only when the water problem is fixed, there's no visible mold or musty smell, and the spot still looks dry a little while later. Source: EPA¹ Stains can remain even after the mold is gone.

Watch out Never mix bleach with cleaners that contain ammonia. It makes toxic fumes. Bleach isn't recommended for routine mold cleanup anyway. If you use any disinfectant, open windows and keep air moving outside. Source: EPA¹ Don't paint or caulk over mold. The paint is likely to peel. Source: EPA¹

See it done

Video by California Department of Public Health Government

When Mold in the Home Is a Problem

Watch on YouTube: 1. When Mold in the Home Is a Problem (English)

Full title on YouTube: “1. When Mold in the Home Is a Problem (English)”2021 · Checked October 3, 2026

Part 1 of a series from California's health department. How to clean a small patch, and when it goes to your landlord, is in the steps.

Video won't load at school or work? No problem. Everything you need is in the steps; the video's just a bonus. Watch it on YouTube later.

If it doesn't work

Landlord ignoring a leak that keeps coming back? EPA says renters can contact local, state or federal health or housing authorities, including the state health department. Source: EPA¹ See Your rights as a tenant.
Musty smell but no visible mold? It may be hidden behind drywall or wallpaper, under carpet, or above ceiling tiles. Pulling off wallpaper can release a cloud of spores, so consider a professional. Source: EPA¹
Mold near the heating or cooling vents? Don't run the system if you think it's contaminated. It could spread mold through the whole place. Source: EPA¹ Tell your landlord.
Mold keeps coming back in the shower? Run the fan or open a window, and clean more often. Source: EPA¹
Thinking about a mold test? If you can see mold, testing usually isn't needed, and there are no federal limits to test against. Source: EPA¹

Good to know

The details, if you want them. Tap a line to open it.

Keep humidity down

Keep indoor humidity below 60 percent, ideally 30 to 50 percent. Vent the dryer and stove outside, use the air conditioner or a dehumidifier when needed, and run exhaust fans or open a window when you shower, cook or run the dishwasher. Source: EPA¹

Stop condensation

Open doors and windows when you can, use fans, raise the temperature a little, and insulate cold water pipes. Source: EPA¹

How it can affect you

For some people, mold causes a stuffy nose, sore throat, coughing or wheezing, burning eyes or a rash. People with asthma or mold allergies can react badly. Source: CDC² Mold can irritate the eyes, skin, nose, throat and lungs even in people who aren't allergic. Source: EPA¹ If you have health concerns, talk to a doctor before you clean.

A message to your landlord (made-up example)

"Hi, this is Jordan in 3B. There's a leak under the bathroom sink and a patch of mold about the size of a dinner plate on the cabinet floor. Photos attached. Can someone come fix the leak this week? I've put a towel down and I'm keeping the area dry until then."

Hiring help

If you hire someone, pick a contractor with mold experience, check references, and ask them to follow EPA's mold remediation guidance. Source: EPA¹

Take it with you

Printable card Download card (PDF)

Sources

U.S. Environmental Protection Agency A brief guide to mold, moisture and your home
Centers for Disease Control and Prevention About mold and your health
U.S. Environmental Protection Agency Mold

Lesson H4.4 · Last checked October 2, 2026 against the sources listed.

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