Which option correctly states the protection factor for a HEPA-filter respirator?

• A. 5 OEL
• B. 20 OEL
• C. 50 OEL
• D. 10 OEL

Answer: (D)

The protection factor is how many times the respirator lowers your exposure to a contaminant, by comparing outside air to what you breathe inside. For a HEPA-filter respirator, the assigned protection factor is 10. That means the air inside the respirator is expected to have one-tenth the concentration of the outside air. In terms of the Occupational Exposure Limit, if the outside air is at the OEL, inside the respirator would be at OEL divided by 10. So the protection factor is 10 OEL. Other values would imply different levels of protection that aren’t typical for a standard HEPA-filter respirator.