A crossover study assessing the protective efficacy of improvised snorkel-based improvised respirators.

Introduction: This study was designed to determine whether improvised respirators based on modified full-face snorkel masks are able to pass a standard qualitative fit test.

Methods: This is a prospective crossover study conducted in 16 staff. Fit-tests were conducted on masks mated to (1) an anaesthetic breathing circuit heat and moisture exchange filter and (2) a CE-marked P3 grade filter. P3 filters were mounted using both epoxy-coated and uncoated adaptors.

Results: None of the tests using anaesthetic filters passed. Only one overall pass was observed using the P3-rated filter mated to the snorkel mask.

Conclusions: These data suggest that improvised PPE designs cannot provide reliable protection against aerosols. Failures are likely due to poor fit, but the suitability of 3D printed materials is also uncertain as fused-filament manufacturing yields parts that are not reliably gas-tight. Improvised PPE cannot be recommended as a substitute for purpose designed systems.