Biocides and Mold

Are biocides useful or required in remediation projects?

Biocides are disinfectant chemicals used to kill germs. In most mold remediation projects, biocides are not a substitute for thorough cleaning. Biocides are of limited use in remediation of indoor mold contamination for two main reasons:

  1. Because applications of biocides are variable, these treatments do not always remove allergens that can lead to allergies in sensitive individuals, nor do they remove other metabolites from mold that can cause adverse reactions in some people. Even though the application of biocides may kill mold spores, the only way to remove the allergens and other metabolites is through the physical elimination of mold and moldy materials by thorough cleaning or removal.
  2. Commonly used biocides do not effectively kill molds. For example, active fungal growth on a surface may produce a spore density of 1 million spores per square inch. Treating this site with a biocide that has an effectiveness of 99.999% would still leave an estimated 10 viable spores per square inch. As such, mold growth may recur if the underlying moisture problem is not resolved.

Biocidal treatments are indicated only when the contaminant is one of the few fungi, such as Aspergillus fumigatus, that is known to cause human infection. This is particularly important in healthcare facilities or other places with occupants who have impaired immune systems or who may be more susceptible to infections.

If a contractor proposes the use of biocides, insist that you see information from the US EPA or Health Canada that it is approved for use indoors to remediate mold in the USA or Canada, respectively.