Mold and Other Microbial Growth

If possible, wet building materials and contents should be dried as soon as possible (preferably within 24-48 hours) to prevent mold growth. When a flood event occurs as part of a widespread natural disaster, the electrical power service and professional services necessary to actually begin cleaning, disinfecting and drying of building materials are not normally available in the 24-48 hours following the event, and can take up to several weeks before roads are cleared, power is on and equipment and people are available to clean, disinfect, and dry the building.  This means that mold and bacterial contamination should be expected after a significant flooding event.  Guidance for small-scale cleanup can be found as follows:  
  • If the overall amount of impacted materials is less than about 10 square feet, the CDC has guidance for homeowners and renters for entry and clean-up.

  • The EPA has guidance on how to address mold clean-up on your own.   

Be sure to read the label and follow all manufacturer’s recommendations when using any chemical disinfectant for cleaning purposes.  Because of the significant risk for adverse respiratory effects and the caustic nature of bleach, the use of bleach for cleaning purposes must be approached with caution.FEMA notes in its guidance on cleaning flooded buildings found that while bleach is convenient as a cleaner and stain remover for hard, non-porous items, it has distinct drawbacks when cleaning water-damaged materials. Many types of bleach are not EPA-registered as a disinfectant.  Furthermore, bleach’s effectiveness in killing bacteria and mold is significantly reduced when it comes in contact with residual dirt, which is often present after a disaster. Also, if bleach water comes into contact with electrical components and other metal parts of mechanical systems it can cause corrosion. Bleach water can also compromise the effectiveness of termite treatments in the soil surrounding the building. 

If significant mold or other sewage contamination has occurred, however, it is recommended that business owners and homeowners seek professional guidance before attempting to clean large amounts of contaminated materials.  Industrial hygienists and other safety and health professionals can anticipate health and safety concerns and design solutions to prevent exposures using guidelines established by government agencies and institutions such as the Institute of Inspection, Cleaning and Restoration Certification.   

Be cautious when considering hiring contractors to perform mold remediation. Some states, such as Florida, Texas, Louisiana, New Hampshire, New York and others require licensure for mold assessors and mold remediators, so be sure to check your state’s requirements.   

Guidelines for evaluating contractors can be found at the following sources:  

Other sources of guidance related to mold response are:  

  • American Industrial Hygiene Association  

Technical guidance for the industrial hygienist includes: