Evaluation of the protective efficacy of a user seal check for N95 respirators through quantitative fit testing in an ambulance crew.

To ensure health and wellbeing of healthcare workers, prevention of infection is essential. Although N95 filtering facepiece respirators (N95 respirators) are potentially effective respiratory protective devices, scientific evaluation for healthcare workers, particularly for ambulance crews has been insufficient. We investigated if N95 respirator user seal checking ensures seal quality through quantitative fit testing among ambulance crews. A user seal check was performed according to the manufacturer's instructions and based on each participant's subjective assessment of fit. A quantitative test was then performed using a dedicated counter. In the results, although the pass rates for both the user seal check and the quantitative test exceeded 50%, the kappa coefficients between the two tests were -0.072 (95%CI: -0.38-0.23), 0.11 (95%CI: -0.11-0.33), and 0.013 (95%CI: -0.31-0.34) for three kinds of N95 respirators respectively suggesting extremely low rates of agreement similar to other reports from health providers. Therefore, we compared the patterns of distributions of the two tests. In the result, probability of agreement of the two tests was determined to be 50%, which was identical to a coin toss. It is unknown what level of protection an N95 respirator will provide when only a user seal check is performed.