The PF for a Negative Air Half Mask is which value?

• A. 10
• B. 50
• C. 100
• D. 1000

Answer: (A)

Protection factor shows how much a respirator lowers your exposure compared with the surrounding air. For a negative-pressure half-face respirator, the assigned protection factor is 10, meaning that with proper fit and use, the air inside the mask should be about one-tenth of the outside concentration. This lower value reflects the seal and airflow limitations of a tight-fitting half-mask without any powered airflow. In comparison, full-face tight-fitting respirators have higher protection factors, and powered air-purifying respirators (especially with loose-fit hoods) can have much higher ones. So the correct value is 10.