Pursuant to the procedure for adding new fit-testing protocols in Appendix A of OSHA's Respiratory Protection Standard, 29 CFR 1910.134, OHD, LLLP (OHD) submitted an application requesting that the Occupational Safety and Health Administration (OSHA) approve a new quantitative fit-testing protocol. The proposed Rapid REDON protocol is a modified version of the existing REDON protocol that would eliminate the 30-second durations for two of the fit test exercises (facing forward and bending over), and also remove the second re-donning of the respirator, thereby reducing the total duration of time required to conduct the fit test. OHD has requested that the submitted protocol be evaluated for approval both with and without removal of the second re-donning. In support, OHD submitted two peer-reviewed articles from the Journal of the International Society for Respiratory Protection describing the accuracy and reliability of the proposed protocol (Kimbrough et al., 2022, 2023). OSHA believes that the information submitted by OHD in support of the Rapid REDON protocol meets the criteria in Appendix A of its Respiratory Protection Standard (Part II) for determining when OSHA will publish a fit-testing protocol for notice-and-comment rulemaking. The Agency is proposing to initiate this rulemaking to determine whether to approve the Rapid REDON protocol.