Assigned Protection Factor 4
Assigned Protection Factor 4 : Assigned Protection Factor (APF) means the workplace level of respiratory protection that a respirator or class of respirators is expected to provide to employees enrolled in a continuing, effective respiratory protection program. (Source: Assigned Protection Factors for the Revised Respiratory Protection Standard, 2009. OSHA. U.S. Department of Labor Publication No. 3352-02 2009.)