Evolution of microbial aerosol behaviour in heating, ventilating and air-conditioning systems – quantification of Staphylococcus epidermidis and Penicillium oxalicum viability

Abstract

The aim of this study was to develop an experimental set-up and a methodology to uniformly contaminate several filter samples with high concentrations of cultivable bacteria and fungi. An experimental set-up allows contaminating simultaneously up to four filters for range of velocities representative of heating, ventilating and air-conditioning systems. The test aerosol was composed of a microbial consortium of one bacterium (Staphylococcus epidermidis) and one fungus (Penicillium oxalicum) and aerosol generation was performed in wet conditions. Firstly, the experimental set-up was validated in regards to homogeneity of the air flows. The bioaerosol was also characterized in terms of number and particle size distribution using two particle counters: optical particle counter Grimm® 1.109 (optical diameters) and TSI APS 3321 (aerodynamic diameters). Moreover, stabilities of the number of particles generated were measured. Finally, concentrations of cultivable microorganisms were measured with BioSamplers (SKC) downstream of the four filters.

Keywords:

• filtration
• heating
• ventilating and air-conditioning
• microbial aerosol
• indoor air

Acknowledgements

This study was supported by the French graduate school École des Mines de Nantes and the French national research and safety institute (INRS) for the prevention of occupational accidents and diseases.