COLLECTION EFFICIENCIES OF COARSE AND FINE DUST FILTER MEDIA FOR AIRBORNE BIOLOGICAL PARTICLES

A newly constructed test system, utilising two optical particle counte rs, has been used to determine the fractional efficiency of fibrous fi lter media for bioaerosols (bacteria, fungal spores and pollen) and no n-biological particles (PSL and limestone). The collection efficiency of coarse and fine dust filters for bioaerosols was comparable with th at of non-biological particles of the same aerodynamic diameter. Parti cle bounce occurred for particles > 5 mu m in diameter at filtration v elocities > 1 m s(-1) when fractional efficiencies for biological and limestone particles declined with increasing particle size and the eff iciency for bioaerosols is higher than that for limestone particles. E xperimentally determined fractional efficiencies agreed well with mode l calculations that take filter inhomogeneities into account while the adhesion probability of biological particles could be described by a formula initially derived for non-biological particles. (C) 1997 Elsev ier Science Ltd.