Air sampling as a “pass/fail” or “present/absent” test for mold in Buildings is unreliable as a “mold test.” Many variables cause a wide range of particle levels in air over short intervals. However this method has a place in a thoughtful Building investigation: air sampling can be useful as a background check for the possibility that there is a large reservoir source which has not yet been found in a Building. But a negative result is of absolutely no confidence, and quantitative work (spores/cubic meter) is invalid unless long-term time-weighted average measurements are made under all varying Building conditions. our own time-lapse sampling proves that particle levels vary by a factor of 10,000 due to common variations in Building conditions such as fan on off, human activity, mechanical disturbance of moldy stuff, etc. While this is an important tool it cannot be relied on in the way most “inspectors” would use it, dashing into a Building and grabbing an air sample. See “Quantitative Analysis” comments below for an elaboration or see Mold Testing: Air samples and their interpretation – a quick tutorial.inspect-ny.com/sickhouse/tutorial.htm
Spores are collected but not spore producing conidiophores, hyphae and other components are collected, making identification incomplete and more difficult than with tape or cultured samples. Spores are desiccated and may be damaged by the collection method, interfering with culture efforts if this follow-up step is needed. In sum, air sampling is useful as a background screen for the possibility that there is a large reservoir source which has not yet been found in a Building, and may be useful to compare relative particle levels between a problem area and a control area, or in an area before and after cleaning. Independent from spore counts, a qualitative analysis of an air sample by an expert technician can provide compelling evidence of a nearby problem mold reservoir in certain cases, for example if the indoor sample contains long chains of Penicillium or Aspergillus spores. These spore chains are so fragile that they break apart quickly while traveling through the air. So spore chains found in (a pre-remediation) indoor sample, even if the total count is low, deserve some further thinking and investigation.