Capture efficiency of portable high-efficiency air filtration devices used during building construction activities

Our plain-English summary of Capture efficiency of portable high-efficiency air filtration devices used during building construction activities, by D.A. Newcomer, P. LaPuma, R. Brandys, et al (Journal of Occupational and Environmental Hygiene, 2018).

The study

• Authors: D.A. Newcomer, P. LaPuma, R. Brandys, A. Northcross
• Journal: Journal of Occupational and Environmental Hygiene
• Published: 2018;15(4):285-292
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The portable high-efficiency air filtration (PHEAF) device is used to control particulate matter (PM) generated from construction-type activities occurring within the built environment. Examples of activities where PHEAF devices are mobilized include building renovation, asbestos abatement, remediation of microbial contamination, and lead-based paint projects. Designed for use on short-term, temporary projects the PHEAF device captures airborne PM using a high-efficiency particulate air (HEPA) filter. This study sought to evaluate the capture efficiency of the PHEAF device in a field setting. An aerosol generator and photometer were used to measure particle penetration through 85 PHEAF devices. Average overall capture efficiency ranged from 41.78% to ≥99.97% with more than 88% of the tests failing to achieve 99.97% capture efficiency. Approximately 73% of the PHEAF device sample population failed to demonstrate HEPA performance criteria during any test round. A higher occurrence of PM concentrations measured around the perimeter of the filter suggested the presence of bypass leakage. While PHEAF devices were effective in capturing a significant quantity of aerosol test agent, these findings suggest that routine testing of the PHEAF device should be conducted to validate performance.

In plain English

This field study tested portable high-efficiency air filtration (PHEAF) devices. The authors describe these as used in asbestos abatement and other construction work. The 85 devices were controlling dust during interior renovation of a twelve-level building and were tested 340 times between May 2012 and February 2015. Testers blew an oil aerosol (PAO) into each unit and measured how much came out the exhaust. A unit passed if it captured at least 99.97%. Metal box-style units passed in 26 of 324 tests (8%), with a mean capture of 94.81%. The polyethylene-cabinet units passed in 13 of 16 tests (81%), with a mean of 99.96%. Capture was generally poorer around the edges of the filter than at its center, which the authors took to suggest air leaking around the filter. Among 23 units tested before and after new HEPA filters were fitted, the pass rate went from 21.7% to 8.7%, a change that was not statistically significant. The authors concluded that most devices did not consistently meet HEPA criteria and that frequent testing is justified.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Field evaluation of air filtration equipment, with repeated testing of the same devices over several rounds
• Who was studied: 85 portable high-efficiency air filtration (PHEAF) devices deployed during interior renovation of a building across twelve floors, tested May 2012 to February 2015. In total there were 340 tests over 9 testing rounds. Most were metal box-style units; two had high-density polyethylene cabinets.
• Exposure: Devices were challenged with a Poly-Alpha-Olefin oil (PAO) test aerosol at the intake side, and penetration was measured at the exhaust with an aerosol photometer. Passing required at least 99.97% capture efficiency. The renovation involved demolition and replacement of concrete, gypsum wallboard and vinyl floor tile.
• Main results:
  • Metal box-style devices (models A, B, D, E, F and H) met the 99.97% criterion in 8% of tests (26 out of 324).
  • High-density polyethylene cabinet devices (models C and G) met the HEPA criterion in 81% of tests (13 out of 16).
  • Mean capture efficiency was 94.81% (SD = 14.765) for metal box-style devices and 99.96% (SD = 0.115) for polyethylene-cabinet devices.
  • 16 of the 85 devices changed between pass and fail from one sampling round to another.
  • Of 52 units that had their HEPA filter replaced, 23 were tested both before and after. Among these 23, the pass rate was 21.7% before replacement and 8.7% after. The change in pass-fail classification was not statistically significant (p = 0.0833). Five of the 23 showed improved capture efficiency after replacement and 18 showed reduced capture efficiency.
  • Across the 9 filter sectors of metal box-style devices, average capture efficiency ranged from 92.52% to 98.05%. The middle-center sector (sector 5) had the highest. Sector 5 was most often the best-performing sector, which was statistically significant (p less than .0001).
  • The least effective sectors (below 84% capture efficiency) were mostly the upper right sector (sector 3) and the lower perimeter sectors (sectors 7 to 9).
  • There were 14 instances, in 7 units, where at least one filter sector showed minimal or zero capture efficiency.
  • Ambient temperature and relative humidity showed a slightly positive correlation with capture efficiency, but the association was not statistically significant.
• The authors' conclusion: The authors concluded that most PHEAF devices do not consistently capture at least 99.97% of a test aerosol. They also concluded that reduced capture around the filter edges suggests bypass leakage, and that the findings justify frequent testing of these devices.
• Limitations the authors state:
  • Testing in the field meant the true cause of a failed test could not be confirmed.
  • Because few polyethylene-cabinet units were tested, the study could not establish that one design type performs better than another.
  • It is unknown whether damaged HEPA filters were included in the before-and-after replacement comparison.
  • The age of the HEPA filters installed before replacement was unknown.
  • Test data from before and after filter replacement were not available for all units.

Topics

Medical terms in this study, explained in our Lexicon: Abatement.

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