Powered, Air-Purifying Particulate Respirator Filter Penetration by a DOP Aerosol

In 1995, new certification requirements for all nonpowered, air-purifying particulate filter respirators were put in place when 42 CFR 84 replaced 30 CFR 11. However, the certification requirements for all other classes of respirators, including powered air-purifying respirators (PAPRs), were transferred to 42 CFR 84 from 30 CFR 11 without major changes. Since the inception of 42 CFR 84, researchers have learned that the efficiency of electrostatic filter media, in contrast with mechanical filter media, can be rapidly degraded by oil aerosols. Further, confusion may exist among respirator users, since electrostatic PAPR filters have the same magenta color assigned to high-efficiency filters for nonpowered particulate respirators that have been tested and certified for use against oil aerosols (i.e., P100 filters). Users may expect that the magenta color of certified PAPR filters indicates suitability for use against oil aerosols. This may not be the case. To illustrate the potential degradation of electrostatic PAPR filters, new filters certified under 42 CFR 84 were tested using a TSI model 8122 Automated Respirator Tester against charged and neutralized DOP aerosols with intermittent loading schedules. The performance of a magenta-colored electrostatic PAPR filter—one for which the manufacturer's user instructions appropriately indicates is not suitable for use in oily environments—was compared with the performance of several mechanical PAPR filters. In tests against both DOP aerosols, the electrostatic PAPR filter showed a significant decrease in performance at DOP loadings exceeding 400 mg, whereas mechanical filters showed no significant change in the performance except at extremely high loadings. The decreased performance of the electrostatic PAPR filter was found to be significantly greater when tested against a neutralized DOP aerosol when compared with a charged DOP aerosol. While laboratory tests show that the filtration efficiency of this electrostatic PAPR filter degrades with exposure to DOP aerosol, the observed laboratory degradation may or may not affect workplace performance, as similar degradation has not been verified in workplace studies. Based on these laboratory results, a proposed method for evaluating high-efficiency PAPR filters is presented. This proposed method would ensure that high-efficiency PAPR filters (≥ 99.97% efficient and magenta in color) meet critical performance criteria when loaded.

Keywords:

• aerosol
• dioctyl phthalate (DOP)
• electrostatic
• filter efficiency
• powered air-purifying respirator (PAPR)
• respirator

ACKNOWLEDGMENTS

The authors would like to thank Bill Miller of the NIOSH Division of Respiratory Disease Studies, Field Studies Branch for his help with statistical analysis. We would also like to thank Molly Pickett-Harner for her editorial assistance.

The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health. Mention of a commercial product or trade name does not constitute endorsement by the National Institute for Occupational Safety and Health (NIOSH) or the authors.

Notes

^A 3M Company acquired Racal in 1998, but the products tested were purchased before the buyout and were, therefore, Racal products.

^B Calculated from manufacturer estimates

^C 115 LPM for tight-fitting PAPRs or 170 LPM for loose-fitting PAPRs divided by the number of filters used in the standard configuration

^D User instructions supplied with filter clearly state that these filters are NOT for use against oil aerosols

^E Calculated from actual filter measurements

^F Maximum flow rate attainable on the TSI 8122 Automated Respirator Tester.

^A Days of aerosol loading on the filters. The loading schedule for each filter incorporated 3 consecutive days where the filters were left untouched to simulate a long weekend. The weekend simulation did not fall at the same point in the loading schedule for each filter. However, no differences in penetration results were noticed as a result of the weekend simulation, regardless of where it occurred in the loading schedule.

^B Maximum penetration at 667 mg DOP per filter (2000 mg total load divided by 3 filters).

^C Only one filter was tested on Day 5.

^D One filter was tested for 7 hours instead of 8 hours. This same filter was the only one tested on Day 5.

^E Maximum penetration at 1000 mg DOP per filter (2000 mg total load divided by 2 filters).

^F Maximum penetration at 2000 mg DOP per filter (2000 mg total load divided by 1 filter).

^A Maximum penetration at 667 mg DOP per filter (2000 mg total load divided by 3 filters).

^B Maximum penetration at 1000 mg DOP per filter (2000 mg total load divided by 2 filters).

^C Maximum penetration at 2000 mg DOP per filter (2000 mg total load divided by 1 filter).

^A Maximum penetration at 2000 mg DOP (2000 mg total load divided by 1 filter).