Taking air samples for mold spores is easy. Knowing how to interpret the laboratory results is another matter.
There is no one level of mold that can distinguish a clean and moldy building. Outdoor spore types and concentrations have an important influence on the indoors. Unfortunately, the outdoor types and concentrations of mold vary quite widely over time and space. In other words, some climates during certain times of year will have extremely high concentrations, and other climates at other times of year will have extremely low levels. We can compare the indoors to outdoors, but realize that the outdoor concentration is a moving target!
Nevertheless, sampling may provide useful information and you should research some general guidelines for interpreting results. In this post, I want to highlight two documents that are freely available on the website of Environmental Analysis Associates, Inc. (EAA), a commercial laboratory in San Diego, CA.
The first document is an article that was published in the Journal of Occupational and Environmental Hygiene in January 2005, titled A Regional Comparison of Mold Spore Concentrations Outdoors and Inside “Clean” and “Mold Contaminated” Southern California Buildings. You can download this article by clicking HERE.
The most intriguing recommendations in the article are found in Table V, Suggested Airborne Acceptance or Rejection Criteria. Here are some of the suggestions:
- “Clean Building” less than 2,000 sp/m3 total for all spore types and less than 700 of Penicillium/Aspergillus.
- Possible indoor amplification: 1,000-5,000 sp/m3
- Indoor Amplification likely present: 5,000-10,000 sp/m3
- Chronic indoor amplification: 10,000-500,000 sp/m3
- Inadequate flood cleanup or active indoor demolition of contaminated surfaces: 50,000-10,000,000 sp/m3 with predominant types beyond the common penicillium, aspergillus and cladosporium including Stachybotrys, Chaetomium, Basiomycetes, Tricoderma [sic], Ulocladium, etc.