Evaluation of HVAC filters as a sampling mechanism for indoor microbial communities

HVAC filters are in place for extended periods of time and can serve as integrated air samplers. This paper presents a comparison of bacterial and fungal concentrations and communities in HVAC filter dust and other sampling locations in occupied residences and in the unoccupied UTest House. A DNA-based, culture-independent approach was utilized to characterize the microbial communities. Microbial concentrations and communities in HVAC filter dust samples were not statistically different from those in high surface dust samples in occupied homes. Despite the general similarity in the communities, Proteobacteria were present in greater proportion in HVAC filter dust samples than in surface dust samples suggesting the air origin of this phylum. Gram-positive bacteria were present in greater proportion in occupied residences than in an unoccupied test house, confirming the potential association of this group with occupants. HVAC filter microbial communities were not different from those present in a composited month-long indoor air sample providing preliminary evidence that filters could be a viable option for long-term investigation of airborne biological contaminants.

Research highlights
► Microbial communities in HVAC filter dust not different from those in high surface dust in residences.
► Greater Proteobacteria in HVAC filters than on high surface samples.
► Greater gram-positive bacteria in residences than unoccupied test house.
► Microbial communities in HVAC filter not different from composited indoor air.
► HVAC filters show promise as integrated indoor samplers for microbiological contaminants.