Evaluation of filter media options for high volume PM2.5 sampling

Authors: LI, HUAN - Texas A&M University; Wanjura, John; FAULKNER, WILLIAM - Texas A&M University; LACEY, RON - Texas A&M University

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2018
Publication Date: 12/10/2018
Citation: Li, H., Wanjura, J.D., Faulkner, W.B., Lacey, R. 2019. Evaluation of filter media options for high volume PM2.5 sampling. Applied Engineering in Agriculture. 35(2): 205-209. https://doi.org/10.13031/aea.13010.
DOI: https://doi.org/10.13031/aea.13010

Interpretive Summary: Ambient concentration measurements of particulate matter less than 2.5 micrometers (PM2.5) used in the determination of regional National Ambient Air Quality Standards (NAAQS) attainment status are currently collected using low volume sampling equipment. A desire to develop sampling methodologies and equipment which utilize higher air flow rates (high-volume) has been expressed by EPA and state regulatory agencies. Concerns regarding filter media selection for aerosol sampling are three-fold. First, low-volume PM2.5 samplers utilize 47 mm diameter polytetrafluoroethylene (PTFE) filters to capture particulate matter for gravimetric analysis. Filters required for high-volume sampling are considerably larger (20.3 x 25.4 cm) and the cost of these filters constructed from PTFE would be quite high relative to low-volume filters ($73 vs $6 per filter). Second, during weighing, handling, and sampling, filters may lose mass, leading to a negative bias in corresponding mass concentrations. Third, artifact formation may occur on some filter materials where gas-to-particle conversions may lead to positive biases in mass concentration measurements. Improvements to low-cost alternative filter media made from glass fibers have been made in recent years such that the alkalinity values (which affects artifact formation) are similar to that of PTFE filters. Thus, the objective of this paper is to compare filter handling losses between recently-manufactured PTFE, glass fiber, and cellulose filters to determine their suitability for use in a high volume PM2.5 sampler. Due to high mass loss during handling processes, the cellulose filters tested in this study are unsuitable for high volume PM2.5 sampling. Glass fiber filters demonstrated a lower mass loss than PTFE filters during handling, and glass fiber filters are now commercially available with alkalinity values similar to PTFE filters. Therefore, glass fiber filters similar in specification to Whatman EPM2000 filters should be considered acceptable substitutes for PTFE filters for use in high volume PM2.5 sampling.

Technical Abstract: Cellulose, polytetrafluoroethylene (PTFE) and glass fiber filter media were evaluated under controlled conditions to determine their suitability for high volume PM2.5 sampling. Mounting tests were conducted in a laboratory environment. Mass losses were observed for all three filter types during the mounting process. Cellulose filters had the highest average mass loss after the first mounting event (2.24 mg), which would introduce significant bias in measured PM2.5 concentrations, making this type filter unsuitable in high volume PM2.5 sampling. Mass loss was lowest from the glass fiber filters, and glass fiber filters are now commercially available with alkalinity values similar to PTFE filters. Therefore, glass fibers filters similar in specification to Whatman EPM2000 filters should be considered acceptable substitutes for PTFE filters for use in high volume PM2.5 sampling.