Spore trap sampling

Spore trap sampling involves collecting airborne particles on a filter membrane or adhesive-coated slide by drawing air through or over the collection medium, respectively.  The collection medium is then analyzed by transmitted light microscopy, typically at 600–1000 × magnification.  A number of different collection devices may be used for spore trap sampling of which the most common are 1) mixed cellulose ester membrane (MCEM) filters; and 2) slit impactors such as the Allergenco D or Air-O-Cell® cassette.

The normally high minute-to-minute variability in levels of airborne spores greatly limits the utility of short-term quantitative air sampling data. This large intrinsic source of variation also minimizes the importance of counting method as a significant source of error. The most critical source of error in spore trap analysis qualitative, involving the identification of spores.  Spore trap analysis is one of the most technically challenging tasks in environmental mycology, requiring considerable skill and experience on the part of the analyst, to identify spores accurately, and to differentiate them from other airborne particles.  A good spore trap analyst requires years of experience not just analyzing spore trap samples but examining whole specimens from field collections in order to learn the full variation of fungal structures as well as particles that might be confused with them.  This level of experience cannot be trained in a short time, and it cannot easily be acquired by individuals lacking advanced training in mycology or botany.


Spore trap sampling has an advantage over culture-dependent methods by permitting the enumeration of fungal particles regardless of culturability or viability.  Because of this, spore trap sampling is sometimes incorrectly referred to as a “non-viable” sampling method; however, it more appropriately should be called a “total” sampling method, since both culturable as well as non-culturable propagules are counted.  The greatest limitation of spore trap sampling is its inability to allow low-level identifications of spores due to the lack of diagnostic features on many spore types.  By contrast, culture-dependent methods have the advantage of access to a variety of cell types for a given fungus, as well as a living culture that could be submitted to physiological tests, allowing other distinguishing characteristics to be evaluated. As such, spores counted in spore traps can only be identified presumptively based on their size, shape and color.




  • Most manufacturers recommend sampling volumes of 150 L for generally clean indoor environments and 75 L for environments suspected to be overly dusty, or for the collection of outdoor comparison samples. Sampling volumes lower than this (e.g. 10-25 L) may be helpful in areas that are highly dusty, such as remediation enclosures or dust-generating industrial processes.
  • At least one field blank should be collected for every 10 field samples taken. Field blanks should be handled in exactly the same manner as test samples except that air must not be drawn through them.
  • Following collection, samples and blanks should be re-sealed, labeled and arranged in a clean box or bag away from moisture and light until analysis.