How to clean black mold: what works, what to throw out, when to stop

Step by step: how to clean black mold

Safety first. Wear an N-95 respirator, long gloves and goggles without vent holes, and open windows before you start. Keep children, pets and anyone with asthma or a weak immune system away from the work. The EPA advises professional help when mold covers more than about 10 square feet (roughly 3 by 3 feet), follows sewage or flood water, or is in your ductwork. Never mix bleach with ammonia, vinegar or any other cleaner.

1. 1

   Size up the growth and the cause

   Measure the moldy area and look for the moisture behind it: a dripping pipe, a leaky window, condensation, or a shower with no fan. If the patch is larger than about 10 square feet, stop here and call a mold remediation company, as the EPA advises. Black spots will return within weeks if the area stays wet.

2. 2

   Gear up and open the room

   Put on an N-95 respirator, long gloves, goggles and clothes you can wash on hot. Open windows, set a fan in one blowing outward, and close the door to the rest of the house. Turn off forced-air heating or cooling for that room while you work.

3. 3

   Take out what cannot be cleaned

   Bag moldy items that soak up water: cardboard boxes, ceiling tiles, carpet pads, mattresses and stuffed furniture. The EPA notes porous materials may have to be thrown away because mold fills their gaps. Seal each bag before carrying it through the house.

4. 4

   Cut out moldy caulk

   Black mold that sits under clear or white caulk in a tub or window cannot be scrubbed out. Slice the old bead with a utility knife, pull it away, and clean the joint underneath. Recaulk only after the joint has dried for at least 24 hours.

5. 5

   Scrub hard surfaces with detergent and water

   Add a good squeeze of dish detergent to a bucket of warm water. Mist the mold first so spores stay put, then scrub tile, grout, sealed wood, metal and plastic with a stiff nylon brush, using a toothbrush in corners. Rinse the brush in a second bucket often. The black should come off the surface; any gray shadow left in grout is usually stain.

6. 6

   Use diluted bleach on nonporous spots only if needed

   For stubborn stains on tile, glazed ceramic or a fiberglass tub, mix no more than 1 cup of household bleach into 1 gallon of water, the CDC’s limit. Apply it with a sponge, wait about 10 minutes, then rinse. Keep windows open and use bleach alone, never with another cleaner.

7. 7

   Rinse and dry completely

   Wipe everything with clean water, then towel dry. Run a fan or dehumidifier aimed at the area for several hours. The CDC advises drying within 24 to 48 hours, which is what stops regrowth.

8. 8

   Bag your cleanup supplies

   Seal used sponges, rags and gloves in a trash bag and take it straight outside. Wash your clothes on a hot cycle, then shower. Wipe the floor where you worked with a damp cloth.

9. 9

   Fix the moisture and recheck in a week

   Repair the leak, run exhaust fans, or add a dehumidifier so indoor humidity stays below 60 percent. Look at the area again after a week and after a month. If black spots return quickly, there is water you have not found yet.

What is black mold, and is it more dangerous than other mold?

“Black mold” usually means Stachybotrys chartarum, but many common molds look black, and you clean them all the same way. The CDC’s facts about Stachybotrys describe it as a greenish-black mold that grows on high-cellulose materials such as drywall, fiberboard and paper when they stay wet from leaks, condensation or flooding.

The CDC says it is not necessary to find out what type of mold you have: all molds should be treated the same for health risk and removal. It also notes that a link between Stachybotrys and specific health problems has not been proven. That does not make mold harmless. Any mold can cause a stuffy nose, sore throat, coughing, wheezing or itchy eyes in sensitive people, and people with asthma or weakened immune systems are at greater risk.

So the color does not change the plan. The size of the growth, what it is growing on, and who lives in the home decide whether you clean it yourself or call a pro.

How to remove black mold from different surfaces

Hard, sealed surfaces can be cleaned; soft, absorbent ones usually cannot. That is the rule behind the EPA’s home cleanup advice.

How do you clean black mold off walls? It depends on what the wall is made of. On tile, or on painted drywall that is still firm, scrub with detergent and water as the EPA advises, using a cloth or soft brush that is damp rather than dripping so you do not soak the paper face, then dry the wall fast with a fan. If the drywall is soft, crumbling or stained right through, the mold is inside the board and that section has to be cut out and replaced. To get rid of black mold on walls for good, fix what keeps them damp: a leak, condensation on a cold outside wall, or a bathroom with no working fan.

For mold on painted drywall that is still firm, see our wall-specific guide. For grout and tub caulk, cleaning shower mold goes into more detail.

Does bleach or vinegar kill black mold?

Both can, but killing mold is not the goal: removing it is. The EPA’s mold guide explains that dead mold can still cause allergic reactions, which is why it says biocides like chlorine bleach are not recommended as a routine part of cleanup.

Bleach is a reasonable extra step on hard, nonporous surfaces, at no more than 1 cup per gallon of water, per the CDC. It does little for mold inside porous materials, and it can fade fabrics and finishes. Vinegar is a mild acid some people prefer; it is not in the federal cleanup steps, but it is fine on its own for light surface spots. The danger comes from combining products: bleach with ammonia or vinegar releases toxic gas.

When black mold is a job for a professional

Hire a mold remediation professional when the growth is large, hidden or tied to contaminated water. Typical signs:

• More than about 10 square feet of growth, or mold in several rooms.
• Mold after a sewage backup or flood, where the water carried bacteria too.
• A strong musty smell with no visible source, which often means mold inside walls or ductwork.
• Mold in your heating and cooling system. The EPA says not to run the system until it is checked.
• Someone in the home has asthma, severe allergies or a weakened immune system.

The CDC’s cleanup tips are a good summary to hand anyone helping: protect yourself, dry everything, scrub, never mix cleaners, and do not paint over mold.

Mistakes to avoid

• Paying for a mold test to learn the species: the CDC says all mold is handled the same way.
• Bleaching moldy caulk instead of cutting it out, so the black returns in a few weeks.
• Mixing bleach with vinegar or an ammonia cleaner to make it work faster.
• Trying to save moldy carpet, ceiling tiles or a mattress.
• Cleaning without fixing the leak or turning on a fan, which guarantees regrowth.
• Working without a respirator and goggles because the patch looks small.