Performance of powered air-purifying respirators under simulated healthcare work exercises

Powered air-purifying respirators (PAPRs) are an important and commonly used form of respiratory protection in healthcare, particularly during high-risk clinical activities. The main purpose of this study was to determine the simulated workplace protection factor (SWPF) for several PAPR models, investigate the effects of simulated healthcare exercises on individual exercise SWPFs (SWPFi), and monitor for the occurrence of over-breathing during testing. Ten human subjects participated in this study, each performing a series of 10 simulated healthcare exercises lasting two minutes each for five loose-fitting and one tight-fitting PAPR, repeated three times. Two scanning mobility particle sizers were used to measure the aerosol concentration inside and outside the respirator synchronously, with the overall SWPF determined by taking a ratio of the two aerosol concentrations. Significant differences in the geometric mean (GM) of the overall SWPF were found among different PAPR models. A safety factor of 10 (SF10) was applied to the 5th percentile SWPF to adjust for uncertainties between simulated and actual workplace settings. With this factor applied, two PAPRs exceeded the Assigned Protection Factor (APF) of 1,000, one (loose-fitting helmet) exceeded the APF of 25, and three models did not achieve the APF of 1,000. The findings suggest that a safety factor of 10 may be too conservative for PAPRs, and their appropriate application remains an important consideration in SWPF studies. Significant differences in SWPFi were observed across exercises, with lower-demand exercises yielding more conservative protection estimates. Over-breathing was not observed during any of the simulated healthcare exercises. Future studies with larger sample sizes and a broader range of PAPR models are needed to better establish the relationship between safety factor application and the APF, and to further evaluate the effects of exercise on SWPFi. The findings of this study may inform the development of an ASTM draft standard for methods to measure respirator SWPFs.