Recognizing Black Mold: What to Look for and Where to Look

black mold collects in corner of a wall

If you are concerned about toxic black mold in your home, you’re not alone. Black mold is dangerous to humans because it produces mycotoxins that can cause minor ailments like headaches, or major ailments like lung infections and cancer. Luckily, it’s easy to detect. One of the best ways to detect this mold, or "stachybotrys chartarum," in your home is to simply go looking for it. Here are some of the best places to look and the signs to look for when scoping out black mold.

Warning: While not all black mold types are toxic, the toxic type can cause many health issues. If you find any type of black mold in your home, you should purchase a home-safety testing kit or hire a professional to test it immediately. If it is the toxic strain, you should temporarily evacuate your house and hire a professional to get rid of it.

Consider Ideal Mold-Breeding Environments

First, you should consider areas that might be an ideal breeding ground for this contaminant. This dangerous mold needs four things to develop and multiply: oxygen, a moisture source, a food source, and optimal growing conditions. It grows best in dark, wet areas.

Make a list of areas you think are good growing environments and check them thoroughly. Consider the basement, the bathroom, in the attic, and under kitchen sinks. These are the areas of the home where molds are likely to be present.

How to Find Black Mold in Your Home


The first and easiest way to find black mold is by noticing any new smells in your home. It has a dank, musty smell that’s hard to miss. If you detect this odor in your home, chances are good that you have an infestation.


Black mold appears black or a dark green and is often slimy-looking. It often appears in clusters, dotting its environment.

Where to Look For Black Mold


Because this organism feeds on cellulose, any area that is wooden or has a cellulose makeup is a good place to start. It especially likes drywall, so you should look for black patches on your walls. If you see any black patches, you should inspect your drywall closer, as the mold is likely also growing behind the walls.

The Basement

Next, you should inspect the basement. In many parts of the country, a basement is naturally damper than the rest of the home, making it the perfect mold breeding ground. Here, focus on looking for damp areas. Water pipes tend to "sweat" in a humid environment, and they are one of the leading causes of black mold in the home. If your washer and dryer are in your basement, look for water leakage around the faucets and fittings that feed the washing machine.

Also, you shouldn’t forget to check around sump pumps for signs of moisture. Many of the newer furnaces have a humidity control on them and are fed by a water source. Look for leaks and sweating of this fixture. These units also have a drain to eliminate excess water. Ensure the drain is not clogged and is evacuating properly.

The Bathroom

A bathroom is an outstanding place for this toxic substance to develop. It is highly recommended that carpeting not be installed in the bathroom, as moisture from the shower can inundate the carpeting, creating the perfect home for an infestation.

Shower stalls and built-in fiberglass showers should also be checked. Because these units are generally sealed-in, the chances of moisture collecting behind them is greater. Also, check the caulking for cracks, as water, and therefore mold, can collect behind it.

The Attic

Because the government has in recent years set many standards for home energy conservation, attics tend to be tighter and have less opportunity for air exchange between the indoor and outdoor environment. This, in addition to insulation, helps further the opportunity for stachybotrys chartarum to grow.

Look for any moisture collecting in the attic from a possible leakage in the roof structure and inspect closely for dry rot or dampness. Notice the nails that may protrude through the roofing material into the interior. Is there any sign of frost on them in the winter? If so, this indicates a ripe environment for an infestation.

Black Mold Remedies

If you discover any areas that show signs of black mold, you can generally clean it if it is no larger than 10 square feet. Wash the area thoroughly with hot water and detergent, and wipe dry. After the area is dry, apply an application of a fungicide. Although bleach will kill mold on the surface, if it is deeply embedded in the wood, bleach will typically evaporate before reaching the source.

If, through this simple inspection, you determine there is mold present in the home in an area larger than 10 square feet, you should call a professional inspector. Although a homeowner can eradicate mold from the home in small, isolated areas, it takes the expertise of these professionals to determine the proper course of action in ridding your home of this dangerous substance.

Alden Smith is an award-winning author and regular contributor to He writes on a variety of subjects and excels in research.