Distinguish air-purifying respirators (APRs) from supplied-air respirators (SARs).

• A. APRs filter contaminants from ambient air; SARs provide clean air from a separate supply.
• B. SARs filter contaminants from ambient air; APRs provide clean air from a separate supply.
• C. APRs and SARs are the same; both filter ambient air.
• D. APRs rely on a sealed room to provide clean air.

Answer: (A)

APRs clean the air you breathe by filtering or adsorbing contaminants from the surrounding environment. In other words, the air you take in has already been purified as it passes through filters or cartridges on the respirator.

Supplied-air respirators, on the other hand, deliver breathing air from a separate source—such as a cylinder or a remote air supply—through a hose or joined system to the facepiece. You are breathing air that comes from an external, dedicated supply, not directly from the ambient environment.

This distinction is important because APRs depend on the ambient air being breathable and filterable. They won’t protect in atmospheres with insufficient oxygen or contaminants that can’t be effectively filtered. SARs provide a known clean air source, making them appropriate when the surrounding air isn’t safe or reliable.