Quantification of the fungal fraction released from various preloaded fibrous filters during a simulated ventilation restart

This study aimed to demonstrate that particles, especially those associated with fungi, could be released from fibrous filters used in the air handling unit (AHU) of heating, ventilation and air conditioning (HVAC) systems during ventilation restarts. Quantification of the water retention capacity and SEM pictures of the filters were used to show the potential for fungal proliferation in unused or preloaded filters. Five fibrous filters with various particle collection efficiencies were studied: classes G4, M5, M6, F7, and combined F7 according to European standard EN779:2012. Filters were clogged with micronized rice particles containing the fungus Penicillium chrysogenum and then incubated for 3 weeks at 25 °C and 90% relative humidity. The results indicated that the 5 clogged tested filters had various fungal growth capacities depending on their water retention capacity. Preloaded filters were subjected to a simulated ventilation restart in a controlled filtration device to quantify that the fraction of particles released was around 1% for the G4, 0.1% for the M5 and the M6, and 0.001% for the F7 and the combined F7 filter. The results indicate that the likelihood of fungal particle release by low efficiency filters is significantly higher than by high efficiency filters. This article is protected by copyright. All rights reserved.
Source: Indoor Air - Category: Occupational Health Authors: Tags: Original Article Source Type: research