Effects of volume, velocity, and composition on the resistance to synthetic blood penetration of N95 filtering facepiece respirators and other head/facial personal protective equipment

Abstract

Surgical N95 filtering facepiece respirators (surgical N95 FFRs) are National Institute for Occupational Safety and Health-approved N95 filtering facepiece respirators (N95 FFRs) cleared by the Food and Drug Administration for resistance to liquid penetration and flammability. A recent study showed that several N95 FFR models performed as well as surgical N95 FFRs in synthetic blood penetration tests that evaluate resistance to penetration by horizontal projection. This aspect, in addition to the influence of other factors on liquid penetration, are not well studied. To address this issue, the effect of liquid volume (1 mL and 2 mL), spray velocity (450 cm/sec and 635 cm/sec), and liquid composition (synthetic blood and diluted synthetic blood) were evaluated. Four types of common protective devices were studied: N95 FFRs, surgical N95 FFRs, surgical masks, and powered air-purifying respirator (PAPR) hoods. For each protective device type, five models were analyzed using a protocol based on the F1862 ASTM International (2017) test method. Reduced liquid volume had a significant effect in only 3 of 20 models. Increased velocity had significantly greater penetration in 9 of 20 models. Diluted synthetic blood had significantly more penetration in 8 of 20 models. This last result was not expected because, in hydrostatic tests, surface tension of the diluted blood would be expected to reduce penetrability; however, across all models tested, data showed that the diluted spray was more penetrable. The study results suggest that fluid composition may be as important as velocity when considering liquid spray penetration. Furthermore, the penetrability of a spray may be inversely related to the penetrability through direct hydrostatic contact.

Keywords:

• F1862
• FFR
• liquid penetration
• PAPR
• surgical respirator

Acknowledgments

The authors wish to thank the following individuals that provided internal review of this manuscript: Mike Bergman, Zhipeng Lei, and Susan Xu.

Disclaimers and disclosures

The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of a company or product name does not constitute endorsement by NIOSH.

Authors have no competing interests to declare. This research did not receive financial and/or material support from an organization that may either gain or lose financially from the results or conclusions of this research.