Which factor primarily affects the assigned protection factor of a respirator?

The assigned protection factor (APF) of a respirator is fundamentally influenced by the type of respirator used and how well it fits the user's face. The APF is a measure of how much protection a respirator provides against airborne contaminants. Different types of respirators are designed for various levels of hazardous exposure and have distinct capabilities based on their construction, filter type, and sealing characteristics.

A proper fit is equally crucial because even the best respirator will fail to provide adequate protection if it does not form a tight seal around the wearer's face. Factors like facial hair, the condition of the respirator, and proper adjustments can all affect this fit. Without a good seal, contaminants can bypass the filters, leading to insufficient protection. Thus, both the type of respirator and how well it fits are central to determining its assigned protection factor, making this choice the most relevant in understanding respiratory protection in occupational safety.