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Mold Control: Critical Tips on How to Clean Up and Prevent Mold After a Flood

Grainger Editorial Staff

After the hurricane blows through and the heavy rains recede or the snow starts to melt after a blizzard, your problems may be just beginning. Water damage can quickly lead to mold, which could pose serious health risks.

These tips will help you start the cleanup effort and help prevent mold after a flood. And check out this infographic for tips on seven hidden places to look for mold in your facility.

How long does it take for mold to grow after a flood?

The microorganisms that turn into mold colonies are always in the air around us, so mold growth will start quickly—within 24 to 48 hours of water exposure. Mold colonies will continue to grow as long as the moisture level is high. In buildings, mold is most fond of wood, drywall,

What’s the best way to prevent mold after flooding?

The only way to prevent mold from growing is to dry the affected area as quickly as possible. To do this, take these steps:

  1. Open up the building if it’s less humid outside. (In general, you’ll want to open the building during the day and close it up overnight.)
  2. Remove all debris and wet items. Clean exposed surfaces with disinfectants or sanitizers.
  3. Get rid of any soaked porous or absorbent material that you can (like ceiling tiles, papers,
  4. If you can’t get rid of saturated carpeting right away, remove water from it with a carpet extractor or wet/dry vacuum.
  5. Use fans to circulate air into the space and speed evaporation.
  6. Use dehumidifiers to reduce the moisture content of the air and help things dry more quickly, especially in closed areas. A home and office dehumidifier may be enough for smaller areas, but large spaces and moisture-saturated areas may require an industrial/commercial dehumidifier, or even a specially designed restoration dehumidifier.

How long should I run a dehumidifier after a flood?

If possible, run a dehumidifier until porous surfaces in the space have dried out completely. It can take anywhere from two days to several weeks to dry out a flood-damaged building. Materials like plaster and insulation will take a long time to dry, so it may be better to replace them entirely. Until everything is dry, mold can continue to damage the building.

Low relative humidity is what pulls moisture out of these surfaces, and humidity levels below 50 percent will discourage mold growth. You can use a moisture meter to get accurate readings.

What kills mold after a flood?

The American Red Cross and the Federal Emergency Management Agency recommend these cleaning products for mold and mildew removal:

  1. First choice: Commercial mold and mildew removers
  2. Second choice: Washing soda or tri-sodium phosphate (5 tablespoons per gallon of water)
  3. Third choice: A solution of bleach and water (one-quarter cup of laundry bleach per gallon of water)

Remember to use the appropriate precautions and protective equipment for mold remediation when cleaning with bleach, tri-sodium phosphate or other heavy-duty cleaners.


The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.


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