Abstract

Indoor air quality is a topic affecting everyone’s lives, whether it is for occupational safety requirements, environmental or home health concerns. To control airborne particules in indoor environments air handling units containing at least one filtration step are proposed. Bioaerosol and more specifically microbial aerosol are of major concern in offices and public buildings. Fine filters present high filtration efficiency for microbial aerosol which size are between 0.8 and 4µm (F7 filter having a mean filtration efficiency of 80% at 0.4 µm). Once the microorganisms are collected, depending of the environmental conditions, they could develop. The aim of this study was to investigate the antimicrobial efficiency of filters containing Zinc pyrithione which is known for its effect against microorganisms. A consortium of microorganismswas aerosolized from a solution containing Staphylococcus epidermidis, Serratia marcescens (respectively Gram positive and negative bacteria) and fungal spores of Penicillium chrysogenum and was collected onto polypropylene fibrous filter media (F7 EN 779-2002). The influence of three parameters on the microbial survival onto filters was examined: air relative humidity (close to 50% and more than 90%), the effect of the presence or not of Zinc pyrithione (ZPT) as antimicrobial substances and the presence of organic particles’. Quantitative (plate counting) analyses were used to determine the survival after 8 days of the bacteria–fungi consortium collected by the filter. The results demonstrated that for normal F7 filter after 8 days at high humidity the fungal spores’ quantity present onto the filter remain constant but the gram positive bacteria decrease by 2 log and the gram negative by 1 log. In presence of ZPT the behavior was the same for Penicillium and Serratia but for Staphylococcus a 4 log decrease was observed. The lower relative humidity have a stronger effect onto the bacterial survival with no living bacteria extracted from the filter after 8 days but only a 2 log decrease for fungal spores apart from ZPT presence. Used filter clogged with organics particles could show different behaviors.