Which type of respiratory protection is open circuit?

• A. SCBA (open circuit self contained breathing apparatus)
• B. SAR (open circuit supplied air respirators)
• C. PAPR
• D. APR

Answer: (A)

Open-circuit breathing systems deliver breathing gas that isn’t recaptured for reuse; exhaled air is released to the environment. The self-contained breathing apparatus fits this idea because it carries its own air supply in a portable cylinder and provides air on demand, with all exhaled breath vented outside the system. There’s no mechanism to scrub or recycle the wearer’s exhaled gas. The other options rely on air from outside sources or on filtration of ambient air, rather than a self-contained on-person supply, so they don’t fit the open-circuit, on-torso air-delivery model as cleanly.