How many air samples are necessary to find a mold problem?

Sometimes many… and sometimes none! If the mold is visible and you’re looking for a remediation protocol, there’s probably no need for sampling. If the problem is not so clear cut, it may take a few samples.There is no law or regulation regarding the number of samples a consultant should take.  The industry generally relies on the “professional judgment” of the consultant. The problem with this, of course, is that you will always find someone who’s “professional judgment” differs from your own.Mold spore concentrations in the outside air are in constant fluctuation depending on the wind, precipitation, time of day, etc., and the indoor air is usually reflective of the outside air. Taking one sample inside and one sample outside would be similar to flipping a coin twice and drawing conclusions from that. Obviously the more times you flip a coin the more accurate your statistics will be. The same holds true for air sampling. It has been estimated that, in order to have 90% a confidence level in your data, you would have to take three samples and a blank from the problem area, three samples and a blank from a non-problem area, and three samples and a blank from two outdoor locations… three times a day, for three days. That’s 144 samples… No one will pay for that so we have to settle on something in between. The AIHA recommends a minimum of two outside samples and Pacific IAQ agrees. As far as inside samples, we recommend at least one in the problem area(s), and one in a non-complaint area.  For post remediation verification, we recommend two outside, one in the containment, and one outside the containment.