The National Institute for Occupational Safety and Health (NIOSH), National Personal Protective Technology Laboratory (NPPTL) has issued Conformity Assessment Interpretation Notice 2018-1005 Rev 1 regarding facial hair and the selection and use of respiratory protective devices. This revised notice clarifies that people who serve as test subjects for product evaluation or fit testing of respirators must be clean-shaven, as facial hair can interfere with the face-to-facepiece seal or valve function. This revised notice supersedes the October 2, 2006 letter and the August 2018 version of NIOSH CA 2018-1005.