Yes. The Occupational Safety and Health Administration’s (OSHA’s) Respiratory Protection Standard (29 Code of Federal Regulations 1910.134) states that employers shall ensure that an employee using a tight-fitting facepiece respirator is fit tested prior to the initial use of the respirator, whenever a different respirator facepiece (size, style, model or make) is used, and at least annually thereafter. OSHA requires this for both negative and positive pressure tight-fitting facepieces. For more information on fit testing see Quick Tips #140, Respirator Fit Testing Requirements and Procedures.