Mold spores can be found nearly everywhere on earth. But finding black mold is unnerving because of its potential danger, so you want to get rid of black mold as soon as possible. When the spores are exposed to moderate temperatures and moisture, they begin to grow and multiply. Our homes, especially bathrooms and damp basements, can provide nearly ideal environments for mold to thrive.
The good news is that not all mold, even the ones that appear to be black in color, are dangerous. There are three categories of common molds found in households that can have health effects:
- Allergenic molds that can be safely removed by using disinfecting products
- Pathogenic molds that can be controlled with disinfectants (but large colonies require professional treatment)
- Toxic molds that require professional treatment and disposal of all affected materials
What has become known as the dangerous black mold is Stachybotrys chartarum, a colony with a dark green or black slimy surface. It is most often found in homes or buildings that have been exposed to excessive amounts of water and humidity for an extended period of time, especially after a flood. S. chartarum produces trichothecenes, a type of mycotoxin. Exposure to S. chartarum could potentially lead to a wide range of respiratory health effects, though this has not yet been proven.
If you discover extensive mold growth, it is a good idea to have a professional mold removal company come in to test and identify the type of mold present. Your local public health department can offer advice on mold testing and refer you to a mold remediation company. The U.S. Department of Environmental Protection recommends the professional removal of mold colonies that cover more than 10 square feet (roughly a three-foot by three-foot patch).
Small areas of mold growth that are caught early, even in the case of black mold, can be removed with some basic disinfecting supplies and safe procedures.
How Often to Clean Black Mold Growth
As soon as any type of mold is spotted on any surface, the area should be cleaned immediately. Small colonies of black mold can become large colonies in just a few days. Since bathrooms, basements, and any area subjected to high humidity are likely locations for mold growth, they should be checked at least weekly for signs of mold.
Equipment / Tools
- Nylon-bristled scrub brush
- Cleaning cloths
- Spray bottle
- Rubber gloves
- Eye protection
- Face mask
- Chlorine bleach
- Hydrogen peroxide
- Distilled white vinegar
- Cleaning vinegar
- Baking soda
- Dishwashing detergent
Before you begin cleaning to get rid of black mold, open doors and windows to be sure there is adequate ventilation in the area where you are working. If one method doesn't work, rinse the area completely with clean water before trying another cleaner. Wear protective gear like gloves, eye protection, and old clothes that can be washed in hot water to kill any stray spores.
Never mix chemicals, because that can create potentially dangerous gases.
Use Chlorine Bleach
Regular household chlorine bleach, sodium hypochlorite, will destroy mold and remove any discoloration on surfaces. However, it is quite harsh and can harm some hard surfaces and fabrics, so follow these steps before using:
Tile and Grout: Mix one part bleach to 16 parts water (one cup of bleach to one gallon of water) and apply the solution to the mold-affected areas. While wearing gloves, dip a sponge or old cloth in the solution and saturate the mold growth. Allow the solution to remain on the moldy area for at least 15 minutes before scrubbing with a nylon-bristled brush. Rinse the area with water and air-dry or dry with an old cloth. Retreat the area if needed.
Painted Walls and Wood Floors: To clean mold from porous surfaces like wood and drywall, a detergent should be added to the bleach and water solution to help it adhere. Mix one part dishwashing detergent, 10 parts bleach, and 20 parts water. Apply the solution with a sponge or mop, trying not to over-saturate the surfaces. Do not rinse away; just allow the solution to air dry.
Exterior Siding and Concrete: Mix one cup of chlorine bleach to one gallon of water. The solution can be used with a garden sprayer, power washer, or hand-scrubbing. Wet the moldy areas with plain water and then the bleach and water solution, and allow it to work for several minutes. If the mold lightens, move to another area. If stains remain, scrub the area, and then reapply more bleach and water solution. Allow the area to air dry completely. Because bleach can kill grass and plants, rinse down nearby planted areas with plain water.
Treat With Hydrogen Peroxide
Hydrogen peroxide is less harsh and produces fewer fumes than chlorine bleach, but it works more slowly. Be sure the bottle of hydrogen peroxide (three to 10 percent solution) is fresh (fizzes when it touches organic matter), or it will not be effective. Hydrogen peroxide breaks down quickly in sunlight.
Hydrogen peroxide does not need to be diluted for cleaning areas of mold. Pour fresh hydrogen peroxide into a spray bottle and spray it directly onto the moldy surfaces. It should begin to bubble or fizz. Wait for 10 to 15 minutes or until the fizzing stops. Use a scrub brush, sponge, or cloth to wipe away the mold. Repeat if needed.
While hydrogen peroxide is more gentle than chlorine bleach, it can still cause spotting and bleaching on fabrics.
Spray With Distilled White Vinegar
All types of vinegar are acidic, and acids can slowly break down the structure of mold and kill it. Distilled white vinegar is non-toxic but acts much more slowly than chlorine bleach or hydrogen peroxide. While it will kill the mold, the discoloration and stains may remain and require additional scrubbing with a household cleaner.
Distilled white vinegar can be used safely on most porous and non-porous surfaces. Pour undiluted white vinegar into a spray bottle and spray onto the moldy surface. Let it work for an hour. Rinse the area thoroughly with clean water and allow the surface to dry. Use hydrogen peroxide or a diluted chlorine bleach solution to remove any remaining traces of discoloration.
To reach black mold along bathtub edges or tight corners of shower stalls, soak a cotton ball with hydrogen peroxide or distilled white vinegar. Place the cotton balls along the edges or in the corners to clean the areas.
Upgrade your efforts by using cleaning vinegar. Food-grade distilled white vinegar is around five percent acetic acid and 95 percent water. Cleaning vinegar contains around six percent acetic acid. That doesn't sound like much of a difference, but cleaning vinegar is 20 percent stronger than white distilled vinegar and will be more effective in killing black mold spores.
Scrub With Baking Soda or Borax
Sodium bicarbonate (baking soda) and the natural mineral borax each have a high pH that inhibits the growth and survival of mold. Both products are inexpensive and easy to use.
Make a paste of the powders with a few drops of water and apply it to the areas of mold growth. Let it sit for at least 30 minutes and then use a dampened scrub brush to scour the area. Rinse well with fresh water and dry with an old cloth.
Neither product is as effective at killing mold or removing stains as chlorine bleach or vinegar.
Tips to Keep Black Mold Away Longer
- Reduce moisture levels in your home. According to the U.S. Environmental Protection Agency, humidity levels in homes should not exceed 60 percent.
- Repair leaks that keep surfaces wet.
- Add a dehumidifier and use heating and air conditioners to help reduce moisture levels.
- Install moisture barriers in basements.
- Clean mold-prone areas regularly to keep black mold growth in check.
Mold Allergy. Asthma and Allergy Foundation of America.
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Basic Facts About Mold and Dampness. Centers for Disease Control and Prevention.
WHO Guidelines for Indoor Air Quality: Dampness and Mould. World Health Organization.
Mold Cleanup in Your Home. U.S. Environmental Protection Agency.
"OSHA NIOSH Infosheet: Protecting Works Who Use Cleaning Chemicals." Occupational Safety and Health Administration, U.S. Department of Labor.
Mold Course Chapter Two. U.S. Environmental Protection Agency