Which statement correctly describes open-circuit SCBA?

Which statement correctly describes open-circuit SCBA?

• A. Open-circuit uses a finite cylinder to deliver air to the wearer and exhausts exhaled air; closed-circuit recycles exhaled air through scrubbers for longer duration.
• B. Open-circuit recycles exhaled air through scrubbers.
• C. Open-circuit uses a fixed air line.
• D. Open-circuit is identical to closed-circuit.

Answer: (A)

Open-circuit SCBA is defined by carrying a finite amount of air in a high-pressure cylinder that supplies the wearer through a regulator and facepiece, with exhaled air vented to the outside rather than recycled. This means the duration is limited by the cylinder’s volume and pressure, not by any scrubber or loop. In contrast, a closed-circuit (rebreather) recycles exhaled air through scrubbers to remove CO2 and add oxygen, extending how long the user can breathe before needing a refill. The idea of a fixed air line describes a different system that draws air from an external source through a hose, not a self-contained unit, so it isn’t open-circuit. Therefore the statement that open-circuit uses a finite cylinder to deliver air and exhausts exhaled air correctly captures how open-circuit SCBA operates.

Open-circuit SCBA is defined by carrying a finite amount of air in a high-pressure cylinder that supplies the wearer through a regulator and facepiece, with exhaled air vented to the outside rather than recycled. This means the duration is limited by the cylinder’s volume and pressure, not by any scrubber or loop. In contrast, a closed-circuit (rebreather) recycles exhaled air through scrubbers to remove CO2 and add oxygen, extending how long the user can breathe before needing a refill. The idea of a fixed air line describes a different system that draws air from an external source through a hose, not a self-contained unit, so it isn’t open-circuit. Therefore the statement that open-circuit uses a finite cylinder to deliver air and exhausts exhaled air correctly captures how open-circuit SCBA operates.