New Orleans resident searches for salvageable items in her home following Hurricane Katrina.

Mold grows above a switch plate in a flooded home

After flood waters recede, dangerous mold spores can begin to grow within 24 to 48 hours on a variety of household surfaces.


Molds are organisms that are naturally present in the environment and reproduce through tiny spores. These spores are invisible to the naked eye, but can be found floating in the air. 

When mold spores land on a wet or damp surface, they can begin to grow, and this is what happens when we see mold growth inside a home or building. Mold spores will not grow if moisture is not present. Therefore, the key to mold control is moisture control.

Molds produce allergens, which can cause allergic reactions, and irritants which can cause irritation of the eyes, skin, or respiratory system. It can also trigger asthma attacks in sensitive individuals. Certain types of mold can also produce toxins with more serious effects, but this is less common.

Controlling Mold

Indoor mold growth can be prevented or controlled by controlling moisture indoors. If there is mold growth in your home, you must clean up the mold and fix the water problem. If you clean up the mold, but don't fix the moisture problem, then, most likely, the mold problem will come back.

If the moldy area in your home is greater than about 10 square feet, it is recommended to hire a Mold Remediation Contractor. Otherwise, for small areas, you can clean up the mold yourself if you follow the proper precautions and guidelines (See Mold Control and Clean-Up Basics). Remember, it is not enough to simply kill the mold, it must also be removed. Dead mold can still cause allergic reactions in some people.

Last updated November 6, 2018