N95 mask fit failure with extended use: A prospective cohort study

N95 masks are used to protect healthcare workers from airborne infections, but mask leakage can occur with extended use. The objective of this study was to determine the proportion of mask leakage with extended use for up to 4 hours. The primary outcome was N95 mask fit-test failure within 4 hours.

Testing for mask leakage was conducted on 40 healthcare staff, in a single ICU, while performing normal duties. Quantitative mask fit testing (QNFT) was performed using the Portacount method at 1-hour intervals for 4 hours.

Of the 40 participants, 80% were female,75% were nurses, and 20% were doctors. N95 mask failure increased with the duration of mask use (P = .0167). Independent mask failure rates after 1, 2, 3, and 4 hours of usual work activity, were 12.5% (N = 5), 15.0% (N = 6), 18.5% (N = 7) and 20.0% (N = 8) of participants, respectively. Cumulatively, 65% of masks failed by 4 hours but only 27.5% failed by 2 hours.

Failure of N95 mask fit using QNFT increased with time, with 12.5% of participants in this study failing after 1 hour and 65% of participants failing by 4 hours. Our research offers quantitative evidence on the performance of N95 mask fit over time. Understanding mask fit has important implications for infection control and may help inform policy development in preparation for future pandemics.