What to Do If You Find Black Mold in Your Home

Experts weigh-in on removal and safety tips.

black mold on wall
Photo: Getty / Ekspansio

Mold isn't always a bad thing—but it's still not an organism you want growing unchecked in your home. "Some molds are very benign," says Leslie Andersen, vice president of training and launch at restoration company Paul Davis. "And some are really good: Think about bleu cheese, or penicillin, or mushrooms, or beer—all of those have molds in them." But if you find a musty smell in your basement or see a patch of fungal growth in a water-prone area of your home, that indicates a mold you'll want to remove—especially if it's hazardous black mold.

"When people use the term black mold, they're often identifying a type of mold called stachybotrys," says Andersen. While many types of mold grow in circular patterns and boast a shiny finish, black mold differs in a few key ways: It grows in a patchier shape and has a much lighter tone. "It's a dull, kind of chalky mold, reminiscent of if you looked inside your fireplace—that kind of a sooty look," says Andersen. When disturbed, it releases mycotoxins which can cause irritation in the nose, eyes, and lungs. "People wipe it or they touch it, and they start sneezing, they cough, they get runny eyes—it's because the mold spores are off-gassing to make you stop bothering it," Andersen says. "What makes it more dangerous to humans is how it affects our respiratory system. We breathe it in, it goes into our lungs, and folks get very, very serious lung conditions from that type of mold spore."

Where Black Mold Most Often Grows

Black mold grows in areas that stay consistently wet over long periods of time—so you won't find it immediately after your toilet overflows, but you might notice it under the bathroom or kitchen sink where a slow drip has gone undetected. Look for it in "utility closets where your water heater is, basements, bathrooms—anywhere you have the probability for moisture, or even groundwater seepage—basements are famous for that," says Andersen. "It doesn't need dark at all." It's also important to note that black mold isn't the same gunk you might find on grout around an old bathtub—that's more likely to be mildew, which thrives on residual dampness and dirt in your shower.

What to Do for Black Mold

If you see a patch of what you think might be black mold, don't touch it; remember, says Anderson, that disturbing the mold is what causes the spores to release its toxins. "Don't attempt to wipe it or spray it or put any chemical on it—that's just going to make it angry," she says. "The best thing to do is contain it." She recommends covering the entire area with plastic—a bag or dropcloth will work—secured around the outer edge of the mold area (so the tape doesn't touch the spores). "If you have HVAC running into that room, shut the vents so they're not pulling anything into the other rooms," Anderson adds.

Call in a Professional

When you're ready to get professional help to remove the black mold, look for a company with an Institute of Inspection Cleaning and Restoration Certificate (IICRC) or an accredited indoor environmental certification from the American Council for Accredited Certification (ACAC), says Andersen; these indicate that employees have the appropriate training and experience to contain and remove the mold safely. The repairs include two phases: removing the areas where mold is growing, which usually means cutting out and replacing drywall or other materials, and finding the source of the water that's causing the mold.

After the repairs are complete, says Andersen, a third-party indoor air specialist should visit your home for an independent air quality test that will compare the level of mold spores inside to the level outside; you want an indoor spore count that's half the outdoor count. "It should be totally gone," says Andersen. "You should not see anything, and the indoor environmental professional will verify and validate with a scientific test that spore count, making sure it's been cleared and that the homeowners can reuse that room."

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