The class of respirator that offers the highest protection is:

• A. Negative pressure respirator
• B. Positive pressure respirator
• C. Powered air-purifying respirator
• D. Supplied-air respirator with hood

Answer: (B)

Maintaining positive pressure inside the respirator is the key factor that yields the highest level of protection. When the interior of the facepiece or hood is at a pressure higher than the surrounding air, any small leak pushes air outward rather than allowing contaminated air to seep in. This minimizes inward leakage even if the fit isn’t perfect, which is why positive-pressure systems generally offer superior protection.

Relying on negative pressure, where air is drawn in through filters, makes the wearer more vulnerable to leaks in the seal because contaminants can be drawn inward through those gaps. While powered air-purifying and supplied-air hood systems are designed to be protective, the defining advantage here is the positive pressure approach, which provides the strongest protection against ingress of hazardous air.