What is the PF for a pressure-demand SCBA?

• A. 1000
• B. 100
• C. 10000
• D. 10

Answer: (C)

Protection factor is the ratio of contaminant concentration outside the respirator to the concentration inside the wearer’s breathing zone. A pressure-demand SCBA keeps the facepiece at a positive pressure, so any small leaks push air outward rather than letting contaminated air in. This effectively minimizes inward leakage and yields a very high protection factor—ten thousand. That level reflects the exceptionally high protection provided in hazardous atmospheres, far surpassing other respirators that offer lower protection factors.