Mold Testing is a Bad Idea?

/ / Environmental Testing, Healthy Building Inspections & Testing
mold testing

Mold Testing is a Bad Idea?

“Mold testing” is commonly requested. People like the idea of collecting samples and getting actual data back from a microbiological lab, but mold testing results are highly variable and easily misinterpreted. For there to be statistical significance in the results there must be many samples collected, and most project teams are reluctant to spend thousands on lab analysis so a smaller sample size is often used to justify significant decisions.  According to the California Department of Public Health, in most circumstances mold testing is a bad idea.

This sentiment is growing in popularity among leading microbiological detectives, but the public still demands mold testing…

Statement on Building Dampness, Mold, and Health

CDPH Statement on Mold Testing

CDPH Statement on Mold Testing

Excerpt from a September 2011 statement from the CA Dept of Public Health (CDPH):

“CDPH has concluded that the presence of water damage, dampness, visible mold, or mold odor in schools, workplaces, residences, and other indoor environments is unhealthy. We recommend against measuring indoor microorganisms or using the presence of specific microorganisms to determine the level of health hazard or the need for urgent remediation. Rather, we strongly recommend addressing water damage, dampness, visible mold, and mold odor by (a) identification and correction of the source of water that may allow microbial growth or contribute to other problems, (b) the rapid drying or removal of damp materials, and (c) the cleaning or removal of mold and moldy materials, as rapidly and safely as possible, to protect the health and well-being of building occupants, especially children.”

Healthy Building Science agrees with this general approach. Whenever anyone suffering symptoms indoors calls and asks for environmental “testing,” we try and steer them toward a Healthy Building Inspection first. We can tell you so much about a building and identify red flags and strategies to improve your indoor environment without collecting a single lab sample. Our eyes, noses, and tools of the trade can assess the extent of water damage and address the abc’s that CDPH recommends.

Dampness, Mold, and Human Health

Additional excerpt from CA Dept of Public Health (CDPH) Statement:

“Human health studies have led to a consensus among scientists and medical experts that the presence in buildings of (a) visible water damage, (b) damp materials, (c) visible mold, or (d) mold odor indicates an increased risk of respiratory disease for occupants. Known health risks include: the development of asthma, allergies, and respiratory infections; the triggering of asthma attacks; and increased wheeze, cough, difficulty breathing, and other symptoms. Available information suggests that children are more sensitive to dampness and mold than adults.”

There are no US regulatory guidelines for types (genera/species) or quantities of mold. This statement deserves to be bold because it comes as a shock to most people. Nobody knows how much mold is “too much,” or how much mold “will make me sick.” There is general consensus that buildings should not be damp and there should not be evidence of visible mold growth indoors. The health effects stated above can be serious and life threatening. But they are associated with visible indicators not quantifiable lab testing results.

mold testing

Lab manager at Forensic Analytical analyzing sporetraps samples for mold. IAQ Radio Joe Hughes at back right.

When is Mold Testing a Good Idea?

With the exception of research or providing peace of mind, both noble and worthy goals, mold testing should be reserved for:

1) Determining the scope of contamination. In order to determine the extent of contaminatio,n we test in control areas (with no known contamination) and compare the control samples to those collected in suspected areas of contamination. Testing outside and in numerous locations throughout a building allow industrial hygienists to “see” which areas are contaminated and require cleaning or remediation.

2) Determine the type of contamination. Using mold as an example, there are some species of mold that are particularly toxigenic. Some species of stachybotrys and aspergillus (genera) are the most notorious. Environmental testing can determine if there are large quantities of particularly dangerous molds present. (However, this information should not change how proper mold remediation is executed… so some don’t recommend mold testing for this reason.)

3) Clearance testing. Many Indoor Environmental Professionals use lab analysis to compare inside of containment with outside of containment after remediation is completed. While this is contentious too, and many believe the clearance testing performed after mold remediation should just be visual and hydrothermal, this is still a popular use of mold testing.

mold testing

Mold Petri Dish and Sporetrap. Common methods of air sampling for mold testing.

Closing Excerpt about mold testing from CDPH:

“There also is consensus that the traditional methods used to identify increased mold exposure do not reliably predict increased health risks. Therefore, the current practices for the collection, analysis, and interpretation of environmental samples for mold cannot be used to quantify health risks posed by dampness and mold in buildings or to guide health-based actions.”

That’s it folks. Straight from the donkey’s mouth.


Healthy Building Science is an environmental consulting firm which provides mold testing and mold inspection services for commercial, residential, multi-family, buildings, offices, industrial and manufacturing workplaces, hospitals and medical facilities, and single-family homes in the greater San Francisco Bay Area and all of Northern California including the cities of San Francisco, San Jose, Oakland, and Sacramento.