Mold in Carpet: How to Clean It and When to Replace It

Mold needs moisture and food. The EPA says moisture is the most important factor influencing mold growth indoors, and that mold can use organic materials such as paper, cloth and wood as food. Carpet, its backing and the dust caught in it give mold plenty to work with.

Common causes:

• Spills and pet accidents that soak into the pad. TDLR's mold prevention tips say to quickly clean up and dry any liquids that might get on carpets.
• Carpet in bathrooms. TDLR's advice is simple: do not carpet bathrooms.
• Damp concrete underneath. NDSU Extension says moisture seeping through concrete walls and floors will cause moist conditions likely to cause mold growth, including in carpeting. See our mold on concrete guide.
• High indoor humidity. The EPA recommends keeping indoor humidity below 60 percent (ideally between 30 and 50 percent).
• Carpet cleaning that left it wet. EPA's mold course lists making sure that carpets, drapes, furniture, and other furnishings are dried promptly after they have been cleaned as a moisture-control step.
• Leaks and floods. These are the big ones, covered below.

The top of the carpet can look fine while the back and pad are growing mold. The EPA lists the underside of carpets and pads among the places hidden mold grows, and NDSU says mold often grows in carpet padding.

Signs to look for:

• A musty smell. UGA Extension says that with mildew in carpet, usually you will notice a musty, sour odor in the room.
• A spot that stays damp or feels cool and clammy underfoot.
• Stains on the back of the carpet. UGA notes that usually mildew will first grow on the back of the carpet.
• Water stains on nearby baseboards or drywall.

To check, pull back a corner of the carpet from the tack strip in the area that smells worst. Wear gloves and an N95, because the CDC recommends at least a NIOSH Approved N95 respirator when you might disturb mold. If the pad is stained, slimy or smells strongly, you've found it.

You don't need a lab test to act on what you can see and smell. The EPA's disaster guide says sampling for mold is not usually recommended, because you need to clean it up and fix the moisture either way. If you can't find the source, a mold testing company can do an inspection. Our how to test for mold guide explains the options.

It depends on how the carpet got wet, how long it stayed wet, and how far the mold has gone.

Carpet mold removal: clean it or replace it?

The reason porous materials are hard to save: the EPA says molds will infiltrate porous substances and grow on or fill in empty spaces or crevices, so the mold can be difficult or impossible to remove completely. Killing it isn't enough either. The EPA notes that dead mold may still cause allergic reactions in some people.

These steps come mostly from University of Georgia Extension's carpet mildew guidance. Use them only for a small area on carpet that got wet with clean water. The EPA says that if the moldy area is less than about 10 square feet, in most cases you can handle it yourself.

Gear up first. Wear gloves, goggles and an N95. The CDC says do not touch mold or moldy items with bare hands.

1. Stop the moisture and dry the area

UGA's first step is to stop the growth: use a dehumidifier to remove the moisture from the air and carpet, open windows and run fans. It adds that if possible, you should lift the carpet and circulate air underneath. Be careful running electrical equipment near wet carpet.

2. Get sun or light on it

If mildew is on the surface, UGA suggests opening drapes to let sun shine on the carpet. For a rug you can carry outside, it suggests 1 or 2 days of direct sunlight. UGA also gives an optional step: brush a solution of 1 part 3 percent hydrogen peroxide and 5 parts water onto the affected back of the rug and set it in the sun. Test any solution on a hidden spot first.

3. Vacuum, then wash with suds

Vacuum the surface to draw out the mold. Use a HEPA vacuum if you have one, since the EPA recommends HEPA vacuums for final cleanup of mold. Empty or replace the bag outdoors right away: UGA warns that mold spores are being drawn into the bag of the vacuum cleaner.

Then UGA says to sponge the carpet with thick suds made from dishwashing detergent and water, remove the suds with a cloth dampened in clean water, and blot out as much moisture as you can.

4. Dry it completely

Dry the spot fully, with sun, fans or a dehumidifier. If stains remain, UGA lists solvent-based spotters, but warns that solvents can destroy the carpet backing and foam padding. Don't overwet.

5. Skip the bleach on most carpet

NDSU notes that most modern carpeting is made of nylon and should not be treated with bleach. Never mix bleach with other cleaners: the EPA says to never mix chlorine bleach solution with other cleaning solutions or detergents that contain ammonia. Our vinegar vs bleach for mold guide covers why bleach isn't the answer for porous materials.

6. Deal with the leftover smell

For a lingering musty odor, NDSU suggests sprinkling baking soda over the carpet, working it in, leaving it overnight and then vacuum twice, moving in a different direction the second time. If the smell comes back within days, the pad or the floor underneath is still wet or moldy.

Area rugs are easier than wall-to-wall carpet because you can take them outside.

• Small washable rugs. NDSU says washable throw rugs can usually be cleaned adequately in a washing machine. Follow the care label.
• Larger rugs. Take them outdoors for sun and air, following the UGA steps above. Clean outside so you don't spread spores inside.
• Wool rugs. Texas A&M says that if a carpet is wool, do not add bleach.
• Rugs with foam backing, and large rugs soaked by contaminated water. NDSU says wall-to-wall carpet, most large area rugs and rugs with foam backing should be discarded after contaminated flooding, and that professional cleaning is usually not worth the cost except for valuable rugs.
• Valuable or antique rugs. For anything costly or sentimental, the EPA says you may wish to consult a specialist.

Texas floods ruin a lot of carpet. During Hurricane Harvey in 2017, rainfall exceeded 30 inches in many locations, and a few locations had more than 50 inches. The EPA says that if your home was flooded and not dried within 24-48 hours, you should assume you have mold growth, and that mold may be hidden under carpet or cushions.

Texas A&M AgriLife Extension's flood cleanup sheet says:

1. Remove water-logged rugs, carpets, and pads within 48 hours after flooding subsides.
2. Flooded carpet pads should always be discarded and replaced.
3. If you try to save the carpet, spread it outdoors, hose it off, clean it, and rinse with 1 gallon water and 2 tablespoons liquid household chlorine bleach if colorfast (not on wool).
4. Dry the carpet and subfloor thoroughly. Texas A&M warns that if carpet is installed damp, it can mildew.

On a slab, Texas A&M notes that removal of the floor covering will hasten drying of the slab.

Before you throw anything out, document it. Texas A&M advises taking photos for use as an inventory and keeping damaged materials for proof of loss. NDSU adds that you should check with your insurer before cleaning so the work is covered. Our guides on does insurance cover mold and mold after flood Texas cover claims and the rest of the house.

• Keep humidity down. TDLR suggests keeping humidity no higher than 50%, using an air conditioner or dehumidifier. Our dehumidifier for mold guide covers sizing.
• Dry spills fast. EPA says that if wet materials are dried within 24 to 48 hours, mold usually won't develop (EPA).
• Don't carpet wet rooms. Bathrooms, laundry rooms and spaces that flood are poor places for wall-to-wall carpet.
• Dry carpet after cleaning. Run fans and the AC after any shampoo or steam cleaning.

Call for help if the moldy area is larger than about 10 square feet, if mold has spread to the drywall or subfloor, if sewage was involved, or if anyone in the home has asthma or a weakened immune system. In Texas, TDLR says that in most instances, areas of visible mold less than 25 contiguous square feet in area may be cleaned or removed by people who are not licensed. Larger jobs generally call for licensed professionals.

Texas keeps testing and removal separate: a license holder may not perform both mold assessment and mold remediation on the same project. Find a mold removal company in Houston, Dallas or San Antonio, or start from our Texas page. Check any company with our license check tool, and see how we verify listings.

If someone in the home has symptoms, talk to a doctor. A mold test can't diagnose illness, and the CDC says individuals with persistent symptoms should see their physician.