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IGERT Trainees and Affiliates at Cutting Edge of HVAC Filter Research


During the past year, several trainees, affiliates and faculty participants of the National Science Foundation’s (NSF) Integrative Graduate Education and Research Traineeship (IGERT) program in Indoor Environmental Science and Engineering at The University of Texas (UT) focused their research on the primary and secondary impacts of filtration in HVAC systems. Filtration in heating, ventilation, and air conditioning (HVAC) systems is the most widely used approach to protect building occupants and HVAC components from particulate air contaminants. Over 70 million US residences and almost all commercial buildings use a filter. Despite their ubiquity, there is very little academic research on filters. This research is critically important because filters are associated with several impacts on the indoor environment including collection and potential amplification of the indoor microbial community, ozone reactions with the deposited particle cake, and HVAC energy use.

IGERT trainee alumnus Michael Waring (Environmental Engineering), now an assistant professor at Drexel University, developed an innovative model of filtration performance in buildings and used this model to assess filter loading in a variety of residential and commercial building scenarios. His work suggests that filters can rapidly develop a particle cake in an occupied building but that typical low-efficiency filters used in residential buildings are often insufficient to protect building occupants from most particles of concern. Michael also integrated this model with an assessment of secondary organic aerosol (SOA) formation and found that high-efficiency filters will reduce SOA formation, but that filtration technology that emits ozone such as electrostatic precipitators can actually increase exposure to SOA. Michael utilized the work of IGERT affiliate John VerShaw (Mechanical Engineering), who conducted a field assessment of filter bypass, the air that bypasses filter media because of installation issues.

IGERT trainee Brent Stephens (Environmental Engineering) conducted theoretical, field, and controlled test-house assessments of the energy implications of filtration in residential and light-commercial buildings. His findings challenge conventional wisdom that higher efficiency filters require greater energy use because, in smaller HVAC systems, a high pressure drop filter often reduces air flow, which also reduces fan power. Brent’s work is currently being integrated into American Society of Heating, Ventilating and Air Conditioning Engineers (ASHRAE) standards and will be integrated into future editions of the ASHRAE Handbook, the main design guide used in the HVAC industry.

IGERT affiliate Federico Noris explored the use of filters as sampling devices for indoor contaminants. Federico collected filters from a variety of buildings and evaluated the culturable fungal and bacterial concentrations, the microbial community (using DNA-based techniques), and heavy metal concentrations in the filter dust. His work demonstrates the viability of this approach, which avoids some of the problems associated with conventional settled dust analysis and short-term air samples. Significantly, Federico is one of the few researchers who have been able to extract fungal and bacterial DNA from indoor dust samples.

The IGERT filter research described above has lead to seven published journal articles (three more submitted) and approximately 20 conference proceedings. Interdisciplinary aspects include inclusion of dissertation committee members from chemical engineering, biology, and architecture, use of multidisciplinary university-wide resources such as the Institute for Cellular and Molecular Biology DNA sequencing facility, and collaborations with industry and researchers at other institutions.

Address Goals

The research described above focuses on cutting edge research and novel findings related to HVAC filters. For example, major new discoveries from these collective studies indicate that secondary organic aerosols can form due to electrostatic precipitators that are designed to remove particles from air, higher efficiency filters do not necessarily require greater energy use, and HVAC filters can be effectively used as samplers to assess integrated exposure to biological agents in indoor air. These findings reflect important research discoveries made possible through the Indoor Environmental Science and Engineering IGERT program at the University of Texas at Austin.

A large number of journal papers and conference presentations have evolved from this work. Further, Trainees Waring and Stephens have given numerous demonstrations of their work to the general public, as well as to trade organizations and consulting firms. As such, they have engaged in learning how to boil complex research findings down to important findings for the public, practitioners and professionals, who have in turn learned from trainees in our NSF IGERT program.