An investigation of fit test rates of N95 respirators after two to four hours usage in a real-world intensive care unit setting

Healthcare workers in a metropolitan intensive care unit will be invited to undergo fit testing of N95 respirators. They will be tested at baseline and at least two hours later in a real world ICU setting, to assess fit testing rates after 2-4 hours of use. Participants will not be tested if they have exposure to confirmed or suspected COVID-19 patients on that day as this may put the participant or tester at risk of COVID-19. Fit testing will be performed using the FT-10 3M Qualitative Fit Test Apparatus Kit - Sweet (Saccharin) respirator test qualitative test. This is a validated testing protocol as per the standard AS/NZS 1715. The testing protocol is well validated and is described in detail in both the manufacturer’s instructions and elsewhere. Fit testing will be undertaken by the researchers, and 3M have agreed to provide training on carrying out fit testing procedures. The range of respirators available for fit testing is: Proshield N95 size medium Proshield N95 size small Halyard Fluid Shield 3 (Small/Medium) 3M 1860s mask size small BYD CARE Foldable N95 Particulate Respirator (“one-size fits all”) BYD DE2322. 3M Aura 1870+ Trident P2 respirator. These are the currently available brands in the study ICUs. If local supply changes or new respirator designs become available these may also be bested. Participants who fail on one mask at baseline may immediately try fit testing with a different brand. Fit testing is expected to take around 30 minutes per participant. Due to the introduction of formal fit testing in our institution, participants were required to only enter the study using a respirator with which they had passed formal fit testing.