Evaluation of new and conventional N95 fit-testing protocols on equivalence and reproducibility: a study protocol

An N95 respirator is designed to fit tightly and filter airborne particles. Healthcare workers (HCWs), especially those handling aerosols, must complete fit testing to choose the right mask and receive proper training. Traditionally, Occupational Safety and Health Administration (OSHA)'s eight-step protocol was used for N95 fit testing, but in 2019, a shorter four-step version was introduced, cutting testing time. Although the OSHA claims both protocols are equivalent, there is limited empirical support and no research on the reproducibility of the conventional method.The proposed cross-sectional observational study will evaluate the equivalence (i.e. agreement) and reproducibility of the fit-testing results of three different designed respirators tested among Chinese HCWs using both new and conventional fit-testing protocols.The kappa agreement between the new and conventional protocols can serve as an important point of reference for fit-testing policies. If there is a high level of equivalence, both fit-testing protocols could be simultaneously implemented as they would be expected to produce similar results. In contrast, if the conventional protocol is more stringent than the new protocol, conservatively, it would be necessary to exercise caution and suspend implementation of the new protocol. Additionally, the reproducibility of respirator fit testing must be determined. Examining the reproducibility could eliminate uncertainty regarding the ability of a respirator to maintain a proper fit in a real clinical setting.

This study was registered to ISRCTN registry: ISRCTN15612510. The study was retrospectively registered on 28^th May 2025; corresponding link: https://doi.org/10.1186/ISRCTN15612510.