By Doug Hoffman

We get a lot of questions about when mold should be remediated rather than simply cleaned. Part of the confusion comes from the fact that the five states that currently have mold licensing laws don’t agree.  More importantly, none of the thresholds established by these municipalities considers the type of mold, the moisture source feeding the mold, or the reality that even a very small amount of mold (smaller than the established square footage threshold) could be harmful to the occupants.

To clarify the discussion, let me first define two words that are often erroneously used interchangeably: remediation and sanitization. Remediation is the actual removal of contaminated construction materials to locate and repair the moisture/water source that is feeding the mold.  The primary purpose of remediation, therefore, is to access and resolve the water source.  Sanitization is the process of using a good biocide to lower the microbial count by cleaning the surface and does not involve gross demolition.  These are clearly two different approaches to addressing mold, so how do you decide when to use which process?

When determining how to best address a mold problem, it’s important to consider the amount of mold, the type of mold, and the moisture content of the substrate behind it.  Remediation would take place when:

  1. There is 10 square feet of visible mold.  When the states established their thresholds, and 10 square feet is the most conservative of the five, they did not consider whether that mold would be in one place or spread throughout the environment.  We suggest that the 10 square feet of visible mold would represent mold either contiguous or cumulative in a single air conditioning coverage area.  This allows the remediator to segment the project based on whether the mold has been or could be spread throughout the entire living environment.  For instance, in a two- story home where there is an air conditioning system on the first floor and one on the second, with the second floor contaminated and the first floor not, a remediation process could be isolated to the second floor.
  2. Zero-tolerance mold is present.  We consider five molds to be zero-tolerance molds, either because they are water sensitive or highly toxic, and these should always be remediated: Stachybotrys, Chaetomium, Fusarium, Memnoniella, and Trichoderma.
  3. The moisture content of the substrate on which the mold is growing is greater than 17%. Mold needs water to grow and can get that water from the air (like air infiltration problems, elevated relative humidity, or poor insulation) or from a water source (leaky pipe, roof leak).  When moisture content is elevated behind mold growth, remediation is usually recommended so that the water source can be removed or repaired.

These three factors provide a common-sense benchmark for determining if remediation or sanitation should be used in addressing mold. Although mold is a serious issue that must be resolved, the reality is that, in many cases, remediation is unnecessary and sanitization could suffice.  Remediation is expensive, so we’re talking about a less expensive and less disruptive solution in sanitization.  If it is appropriate to use sanitization instead of remediation, the process is faster and more cost effective, which will certainly make your customers happy.


Doug Hoffman is the CEO of NORMI, the National Organization of Remediators and Mold Inspectors. He can be reached via e-mail at doug@normi.org.