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, FusariumFusarium sp. are found on a wide range of plants and in humidifiers. Several species in this genus can produce potent trichothecene toxins. Some species also produce vomitoxin on grains during unusually damp growing conditions. Poisoning by these toxins occur primarily through ingestion of contaminated grains or possibly inhalation of spores. The genus can produce hemorrhagic syndrome in humans (alimentary toxic aleukia). This is characterized by nausea, vomiting, diarrhoea, dermatitis, and extensive internal bleeding. Fusarium is reportedly allergenic and some species are frequently involved in eye, skin and nail infections. and some species of StachybotrysStachybotrys sp. may produce a trichothecene mycotoxin- Satratoxin H – which is a poisonous by inhalation. The toxins are present on the fungal spores. Stachybotrys sp. grows on building material with high cellulose content and low nitrogen content. Stachybotrys sp. is rarely found in outdoor samples. It is usually difficult to find in indoor air samples unless it is physically disturbed or if it dries out and become airborne. There is controversy about toxigenic effects through inhalation of spores or mycelia. (black mold) produce moist spores that are not easily released into the air. Some other molds such as Chaetomium and PhomaPhoma sp. is a common indoor air allergen. The species are isolated from soil and associated plants (particularly potatoes). It will grow on butter, painted cement and rubber. Phoma sp. may cause phaeohyphomycosis, a systematic or subcutaneous disease. 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.