Abstract
In indoor environments, air sampling normally involves drawing a sample from an air stream or room using equipment based on either the impaction or filtration methods. An international standard regarding sampling methods for the detection and enumeration of molds is about to be proposed. This ISO (ISO/TC 146/Sc 6/WG 10N 27), entitled ″Detection and enumeration of molds - sampling by filtration″ suggests that the process of suspension is necessary in order to spread mold spores filtered on the surface of a filter onto a growth media. However, airborne microbes suspended in air are rarely in the state of naked particles. Therefore, by the suspension process specified by the ISO method, the number of colony forming units (CFUs) on a culture medium will not accurately express the number of bio-aerosols actually suspended in air. The present study was conducted to clarify the behavior of bio-aerosols suspended in air and to demonstrate the inadequacies of a filtration method that uses the suspension process to quantify fungal spores on a filter surface. The authors found that fungal spores suspended in air are coagulation particles and not naked particles, as demonstrated by both the Andersen sampler as well as electron microscopy of W.sebi spores. Furthermore, by the process of suspension, the CFU number was several times the value of fungal spores actually suspended in air.
