In respirator terminology, what does APF stand for?

• A. Assigned Protection Factor
• B. Air Permeability Factor
• C. Annual Protection Factor
• D. Assigned Personal Filter

Answer: (A)

APF stands for Assigned Protection Factor, a rating used to describe the level of protection a respirator provides when it is properly chosen, fitted, and used. It tells you how much the wearer’s exposure to a contaminant is reduced by the respirator in real use. In practice, the concentration of contaminant inside the respirator is the outside concentration divided by the APF, assuming a good fit and correct use. For example, if the outside concentration is 100 units and the respirator has an APF of 10, the inside concentration would be about 10 units. Different respirator types have different APFs, which is how safety professionals determine what kind of respirator is needed for a given exposure level.

This term isn’t about how breathable the material is (air permeability), nor is it a separate factor like an annual or personal filter designation. Those other options don’t match the established terminology for measuring the level of protection provided by a respirator.