Air Quality Test Showed No Mold But Can See Visible Mold

Air quality test is often conducted to determine the level of airborne mold spores. Interpretation of air quality test results is often difficult as the levels of mold spores in the air vary greatly depending on the activity in the room, changes in temperature and relative humidity, ventilation rate and season of the year. During summer for example, indoor mold spore counts can be relatively very high even in homes with no visible mold growth due to infiltration of spores from outdoors.

It’s also possible to have very few airborne spores in buildings with visible mold growth. This is because there are biological differences between the fungi in terms of the way they produce their spores. The Aspergilli and Penicillia, for example, produce large quantities of dry spores that easily become airborne. On the other hand, Fusarium and some species of Stachybotrys (black mold) produce moist spores that are not easily released into the air. Some other molds such as Chaetomium and Phoma produce their spores in enclosed structures (fruiting bodies) and hence these spores may not be detected by air sampling until later when the material dries out or is broken on impact e.g., during renovation.

For viable samples, the spores and fungal materials present in the air may be dead or may belong to molds that cannot be cultured in artificial media. The mold may also be alive but may not be culturable on the detection media used. Therefore a combination of air sampling (both viable and non-viable), surface (e.g., tape-lift) and bulk sampling is recommended. An air quality test alone is not enough to rule out mold growth. See the article Non-viable Fungal Air Sampling Alone May Not Be Adequate.

About Jackson Kung'u

Dr. Jackson Kung'u works for MBL, a laboratory that specializes in identification and enumeration of mold and bacteria commonly detected in air, fluids and bulk samples collected from homes, schools, offices, hospitals, industrial, agricultural, and other work environments. Jackson also provides a unique Mold Training Course on How to Recognize Indoor Mold, Develop Effective Sampling Strategies, Interpret Laboratory Results and how to Control Mold Growth.