Mold and Moisture

Mold is naturally-occurring and can be found everywhere in the environment, both indoors and outdoors. In the outdoor environment, mold helps to break down material such as leaves and dead trees. Mold will grow in areas where moisture is present. Mold growth, which often looks like spots, can be many different colors, and can smell musty.

Health effects

Exposure to mold can cause a variety of health effects, or none at all. Some people may develop symptoms that are similar to an allergic reaction. If you have an existing health condition such as asthma, emphysema or COPD, it can make those conditions worse. The type and severity of the health problem can vary, but often includes headaches, breathing difficulties, skin irritation, allergic reactions, and aggravation of asthma symptoms. If you think you are experiencing a health problem due to mold, you should consult your health care provider.


Since the effect of mold on people can vary greatly, either because of the amount or type of mold, you cannot rely on a mold test to know your health risk. In addition, standards for judging what is and what is not an acceptable quantity of mold have not been set and a mold test or inspection can be quite expensive. If you see mold growth or smell something musty, there is likely mold growing. No matter what type of mold it is, you will need to fix the problem that is causing the mold growth.


Removing the moisture source is the key for getting rid of mold. If you clean up and the moisture is still there, the mold will come back. To prevent mold growth:

After a water leak or flood

  • Fix any leaks in your home’s roof, walls, or plumbing.
  • Clean up and dry out your home thoroughly and quickly (within 24-48 hours) after a flood or water leak.
  • Ventilate the area with a fan or by opening a window.

In a naturally humid space

  • Use a humidistat to monitor the humidity level in your home. Keep the humidity level in your home between 40% and 60%.
  • Use an air conditioner or a dehumidifier during humid months and in damp spaces, like basements.
  • Use a ventilation fan for bathrooms and kitchens. Make sure the clothes dryer is vented outside the house.


If mold is growing in your home, you will need to fix the moisture problem and clean up the mold. Mold can be cleaned from hard or nonporous surfaces using detergent and water. Throw away porous materials that have become submerged or saturated.

The use of bleach is not recommended as a routine practice during mold cleanup. There may be instances, however, when a homeowner uses bleach to remove stains or odor, but in most cases, it is not possible or desirable to disinfect an area. A background level of mold spores will remain but these spores will not grow if the moisture problem has been resolved. It is important to note that dead mold may still cause allergic reactions in some people, so it is not enough to simply kill the mold, it must also be removed.

If you choose to use bleach, always ventilate the area and exhaust the air to the outdoors. Never mix chlorine bleach solution with other cleaning solutions or detergents that contain ammonia because toxic fumes could be produced. Wear non-porous gloves and protective eye wear and follow the manufacturer’s instructions when using bleach or any other cleaning product.