Last Updated on March 4, 2022 by Alarm New England

Mold is a type of fungi found both indoors and outdoors. Mold is not a welcome sight for homeowners: It produces nasty smells, and some varieties of mold can even cause health problems. Black mold is one such variety.

You have probably come across black mold (also known by its biological name Stachybotrys chartarum) in an old house, or maybe even in your own home.

Black mold is a type of fungus, and although it appears to be black at a distance, it can appear dark green upon closer examination. It is those black marks you see on walls, particularly low down near the skirting.

Room walls are an excellent breeding ground for black mold as it loves surfaces that contain cellulose, such as plasterboard, chipboard, or paper. Mold grows in damp, warm conditions. That is why mold is more common in shower rooms, bathrooms, and laundry rooms.


On its own, black mold is not dangerous, but it can release harmful toxins into the environment, affecting air quality and causing health problems for people who inhale those toxins.

That’s why it is important to make sure your home isn’t a breeding ground for black mold. Here’s how to identify black mold in your home, remove it, and prevent it from growing in the first place.

Identifying Black Mold in Your Home

One way of identifying black mold is from its color. Other molds you might observe are usually different colors, but black mold is distinctively black. Black mold grows slowly and only takes on its distinctive black color when it is fully grown. It can sometimes be mistaken for dirt or dust due to its color.


Another big giveaway of black mold growth is the smell: It has a distinctive musty odor, even if you can’t see it.

How to Test for Black Mold

There are now a plethora of mold test kits on the market to help you determine if you have black mold.

With some kits, you can get a result within minutes. With other test kits, you send the results away for analysis by qualified labs, which is likely to get more accurate results.

In general, home testing kits are not reliable enough to make any conclusions. We recommend that you get in touch with experts to determine if you have black mold present in your home, especially if you or other people in your home are experiencing any symptoms or health effects that may be caused by mold.

Symptoms and Health Effects from Black Mold

Mold exposure affects people differently. One person living in a home with black mold may have reactions, while another person living in the same space may experience no physical effects.

Some people have genetic predispositions or immune system responses that make them more sensitive to mold than others. Age and general health can also be factors: The elderly and young children are most affected by exposure to black mold.

The symptoms of exposure to black mold range from fatigue, headaches or migraines, mood swings, tremors, eye irritation, sneezing, and coughing. One of the problems identifying a reaction to black mold is that the symptoms are also common in other respiratory disorders.


If mold exposure or a mold allergy is suspected, a doctor may order allergy tests. An allergy test might involve dropping liquid containing the mold onto the skin and monitoring the reaction.

Preventing and Removing Black Mold

Black mold needs four things to develop and grow:

  • Oxygen
  • A water source
  • A food source
  • Optimal growing conditions

With these four factors in mind, there are certain areas in the home where black mold is more likely to accumulate.

Where to Look for Black Mold

Any drywall areas might be a breeding ground for black mold, as well as areas that are wooden and cellulose-rich. Look closely, because the mold might be growing behind the wall.


The basement is probably naturally damper than other areas of your home, making it an excellent breeding ground for mold. Look around water pipes if you have any, as they tend to sweat in a humid environment. If you have a washer or dryer in the basement, check the inlet and outlet pipes for both.


Another common place for black mold growth is in the shower room or bathroom. Avoid using any carpet in a bathroom, as that would be a perfect home for mold infestation. Bath mats outside the shower or around the toilet should be washed regularly for this reason.


Check the shower stall, at the bottom of shower curtains, and in the crevices in built-in shower screens because moisture can collect behind them.

Finally, another area of the home susceptible to mold growth is in the attic. Look for any moisture collecting in the attic space and signs of frost that indicates water collection.

Black Mold Removal

If you find black mold, you can usually clean it with water and bleach. Keep in mind that bleach will kill surface mold, but it will not get a mold that has penetrated wood. After the bleach and water has dried, apply a fungicidal product.

If your mold infestation is greater than 10 meters in length or height, you should call a professional mold inspector. For mold infestations this extensive, it takes professional expertise to determine the proper course of action.

How to Prevent Black Mold

You can take several steps in your home to prevent black mold.

  • Keep humidity levels in your home as low as possible. Use an air conditioner or humidifier to control humidity.
  • Ensure your home has enough ventilation. Make sure your clothes dryer vents outside the building.
  • Fix any leaks in your roof or leaking pipes so mold does not have the moisture to grow.
  • Clean bathroom and showers regularly with mold-killing products.
  • Remove or replace carpets that have been soaked and can’t dry properly.
  • Don’t use carpets in rooms exposed to water and moisture, like bathrooms, laundry rooms, or damp basements.