Assigned Protection Factors (APF), a new guidance document published by OSHA, provides employers with vital information for selecting respirators for employees exposed to contaminants in the air, according to an agency press release.

OSHA revised its existing Respiratory Protection standard in 2006 to add APFs and Maximum Use Concentration (MUC) provisions. APF means the workplace level of respiratory protection that a respirator or class of respirators is able to provide to workers. The higher the APF number (5 to 10,000), the greater the level of protection provided to the user. APFs are used to select the appropriate class of respirators that will provide the necessary level of protection against airborne contaminants. Such exposures can come from particles or a gas or vapor.

MUC represents the limit at which the class of respirator is expected to provide protection. Whenever a hazard’s exposure level exceeds MUC, employers should select a respirator with a higher APF. MUC means the maximum atmospheric concentration of a hazardous substance for which a worker can be expected to be protected when wearing a respirator.

APF and MUC are mandatory respirator selection requirements that can only be used after respirators are properly selected and are used in compliance with the entire standard. The respiratory protection standard requires fit testing, medical evaluations, specific training and proper respirator use. The standard applies to general industry, construction, longshoring, shipyard and marine terminal workplaces.