MICROBIAL AEROSOL FILTRATION: INFLUENCE OF HUMIDITY ON HVAC FILTER COLONISATION AND THE CONSEQUENCES ON FILTER RELEASE

摘要

Microbial aerosols are captured by HVAC filters and can colonise those filters in appropriate conditions. The aim of the study is firstly to examine the influence of humidity at fixed temperature on microbial growth for two HVAC filtering media (synthetic and glass fibre), and secondly to estimate the microbial release downstream of these filters after microbial growth. An experimental setup has been developed to homoge- neously contaminate several filters simultaneously by nebulising a microbial consortium composed of bacte- ria cells and fungal spores. After filter contamination, the growth of microorganisms onto the filters and measurements of microbial release from the filters were studied after latency in specific conditions of humid- ity and temperature during 48 h and 168 h (which simulate stops of HVAC systems during a weekend and a holiday week). Microbial growth onto the filters was evaluated after extraction by CFU counting. In order to study release the tested filters were placed in a column where airflow, representing a restart of the HVAC ventilation, was imposed. The microorganisms released downstream of the tested filters were recovered by a high efficiency collection filter and evaluated by CFU counting.