Three new NIOSH publications provide answers to frequently asked questions about respiratory protection topics. The in the series helps users understand the difference between respirator reuse and extended use, when filtering facepiece respirators can be safely reused, and how long employees should wear the same filtering facepiece respirator. The answers questions about the recommended frequency of fit-testing, facial hair and fit-testing, and fit-testing requirements for powered air- purifying respirators. The describes how to do a user seal check while wearing a filtering facepiece respirator. According to NIOSH, a user seal check is a procedure conducted by the respirator wearer to determine whether the respirator is being properly worn. The publication clarifies that a user seal check cannot be considered a substitute for fit-testing.  Learn more on NIOSH's .