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

Abstract

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 was 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 three weeks at 25°C and 90% relative humidity. The results indicated that the five 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.

Removal of SARS-CoV-2 using UV+Filter in built environment

“…Several studies have shown that stress-resistant spores can remain viable over a prolonged period of time and even grow in the filter media ( Forthomme et al, 2014 ). The spores collected on filters can be re-aerosolized during replacement or maintenance ( Morisseau et al, 2017 ), thereby posing a health risk. In order to overcome this disadvantage of pleated fibrous filter, UV+Filter system is developed for indoor ventilation systems.…”

“…The risk of Fibrous-filter is re-aerosolization of deposited particles (e.g. spore) during replacement or maintenance ( Morisseau et al, 2017 ). Professional property service and system maintenance were needed for Fibrous-filter users.…”

Evaluation of Antimicrobial Effect of Zinc Pyrithione against Airborne Fungi and Bacteria Growth Collected onto New and Loaded HVAC Fibrous Filters

“…The microbial growth onto fibrous filters is influenced by the air humidity [8], but even more by the water retention capacity of the filters [8,10]. Water is sorbed by the fibers of the filter and/or by the particles collected by the filter according to the hydrophilic characteristics of the fibers and the particles.…”

“…Microbial growth onto HVAC filters was observed in the literature under laboratory conditions [7][8][9][10], and also in real conditions [11,12], with possible degradation of the Processes 2021, 9, 1528 2 of 13 microbial indoor air quality. To address this issue, innovative air filters with photocatalytic properties [13] or containing antimicrobial treatments are designed to be implemented in HVAC systems, or in portable room air cleaners or automobiles.…”

ZeBox: A novel non-intrusive continuous-use technology to trap and kill airborne microbes

“…Filtration [2] and electrostatic precipitation [3] belong to the latter category. Microbes trapped inside filters can multiply in situ [4,5,6,7,8]; such filters are detrimental to indoor air quality and hazardous during their disposal. They also offer high flow resistance which translates to high operating power consumption [9,10].…”