ASHRAE - American Society of Heating@ Refrigerating and Air-Conditioning Engineers@ Inc.
Scope
INTRODUCTION Indoor air quality researchers typically focus their attention on biological@ chemical and particulate contamination of indoor environments and the health effects and discomfort that these contaminants may cause. Indoor environmental investigations typically rely on short-term sampling techniques that provide only a snapshot of contaminant concentrations in the indoor environment at the time of sampling. HVAC filter dust is a potential resource that has received less attention and may enhance our understanding of indoor occupant exposure. Filters are typically in place for extended periods of time and have the potential to serve as long-term samplers of the indoor environment. Furthermore@ HVAC filter dust can be collected with minimal effort and analyzed for a broad range of contaminants. This paper focuses on bacteria@ fungi@ and heavy metals captured on HVAC filters and investigates how these parameters vary with filter and building characteristics. Several studies have measured the concentration of bacteria and fungi in indoor environments@ especially in air and settled dust (e.g.@ Bouillard et al.@ 2005; Dales et al.@ 1997; Verhoeff and Burge@ 1997). However@ the reported concentrations are difficult to compare because they vary considerably depending on sampling technique and sampling location@ among other factors. An alternative approach for investigating air and settled dust would be to analyze the dust that collects on HVAC filters. A recent study has suggested that HVAC dust may provide an integrated measure of airborne contamination levels in an indoor environment (Tringe et al.@ 2008). HVAC filters are able to retain biological particles and microorganisms can survive@ accumulate@ and@ under certain conditions@ multiply on HVAC filters (Farnsworth et al.@ 2006; Foarde and Hanley@ 2001; Kemp et al.@ 1995; Kemp et al.@ 2001; Moritz et al.@ 2001; Simmons and Crow@ 1995). In addition@ a number of studies suggest a relationship between Sick Building Syndrome (SBS) symptoms and the presence of microorganisms on filters (e.g.@ Schleibinger and Ruden@ 1999). Several researchers have also studied heavy metal concentrations in house dust and the correlation with potential indoor and outdoor sources and particle size distributions (Al-Rajhi et al.@ 1996; Chattopadhyay et al.@ 2003; Decker et al.@ 2002; Kim et al.@ 1998; Tong@ 1998). Despite these efforts@ we are not aware of any research that utilizes HVAC filters as samplers to characterize metal concentration levels indoors or that examined the influence of HVAC systems and potential sources on metal concentrations found on the HVAC dust. While both microbial populations and metals found indoors have been studied@ the relationship between their presence in HVAC filter dust and critical characteristics of both the particular HVAC system and the building remains unclear. This research compares the contaminant levels found in HVAC filters with different filter efficiencies and provides insight into potential sources of contamination. This investigation is part of a broader evaluation of the utility of using filters as samplers for the indoor environment.