One of the major classes of fungal organisms. Ascospores are ubiquitous in nature and are commonly found in the outdoor environment. This class contains the “sac fungi” and yeasts. Some ascomycete spores can be identified by spore morphology, however; some care should be exercised with regard to specific identification.

They are identified on tape lifts and non-viable analysis by the fact that they have no attachment scars and are sometimes enclosed in sheaths with or without sacs. Some fungi that belong to the ascomycete family are the sexual forms of Penicillium/Aspergillus, Chaetomium and Pleospora. This group contains possible allergens, mycotoxin producers and opportunistic human pathogens.

Rain and high humidity may rupture the ascus, disbursing the spores, which is why during these weather conditions there is a great increase in counts.