Anaesthesia 2020, 75, 962-977 Correspondence modifications to the snorkel adaptor between each joint to reinforce the system. In every case the mask failed during the initial 'normal breathing' phase.It might be speculated that snorkel masks are simply poorly suited for this use. When submerged, a highpressure exists outside the mask which presses it to the face.In air there is no such gradient, so there remains only the force exerted by the head straps to hold it securely. It is not clear that they are sufficient to this task.We recognise we have tested only a single combination of adaptor and mask on a single user, but our data demonstrate that it is essential to properly fit-test before use. It is crucially important to note that fit-testing quantitative methods are mandatory for full-face masks (such as this improvised system) [5]; qualitative fit-testing, using taste-or smell-based substances, is not adequate.It is laudable that people are attempting to ameliorate the shortages of PPE worldwide, but we cannot recommend that staff use improvised equipment in clinical situations without fit-testing. There may be instances in which these systems can be safely used but, as with formal PPE systems, it is clear there is no 'one-size fits all', and to use these improvised designs without proper testing may present a significant hazard to staff.

ObjectiveTo describe success rates of respiratory protective equipment (RPE) fit testing and factors associated with achieving suitable fit.DesignProspective observational study of RPE fit testing according to health and safety, and occupational health requirements.SettingA large tertiary referral UK healthcare facility.Population1443 healthcare workers undergoing quantitative fit testing.Main outcome measuresQuantitative fit test success (pass/fail) and the count of tests each participant required before successful fit.ResultsHealthcare workers were fit tested a median (IQR) 2 (1–3) times before successful fit was obtained. Males were tested a median 1 (1–2) times, while females were tested a median 2 (1–2) times before a successful fit was found. This difference was statistically significant (p<0.001). Modelling each fit test as its own independent trial (n=2359) using multivariable logistic regression, male healthcare workers were significantly more likely to find a well-fitting respirator and achieve a successful fit on first attempt in comparison to females, after adjusting for other factors (adjusted OR=2.07, 95% CI): 1.66 to 2.60, p<0.001). Staff who described their ethnicity as White were also more likely to achieve a successful fit compared with staff who described their ethnicity as Asian (OR=0.47, 95% CI: 0.38 to 0.58, p<0.001), Black (OR=0.54, 95% CI: 0.41 to 0.71, p<0.001), mixed (OR=0.50 95% CI: 0.31 to 0.80, p=0.004) or other (OR=0.53, 95% CI: 0.29 to 0.99, p=0.043).ConclusionsMale and White ethnicity healthcare workers are more likely to achieve RPE fit test success. This has broad operational implications to healthcare services with a large female and Black, Asian and minority ethnic group population. Fit testing is imperative in ensuring RPE effectiveness in protecting healthcare workers during the COVID-19 pandemic and beyond.

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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.