Which breathing device has a design that allows the user to utilize the device for an extended time by recycling exhaled air?

The closed-circuit breathing apparatus is designed to enhance the efficiency of breathing by recycling exhaled air. In this system, the exhaled air is passed through a canister that removes carbon dioxide and replenishes oxygen, allowing the user to breathe air that is filtered and enriched. This recycling feature enables extended usage, making it particularly useful in situations where long-duration respiratory protection is essential, such as in confined spaces or hazardous environments.

In contrast, other devices like the supplied-air respirator relies on a continuous flow of fresh air from an external source. The open-circuit breathing apparatus expels the exhaled air into the environment, which limits the amount of time it can be used since it depletes the air supply more quickly. An air-purifying respirator only filters incoming air rather than recycling exhaled air, making it less suitable for prolonged use in hazardous atmospheres. The closed-circuit system is thus ideal for applications requiring long-term respiratory protection in contaminated environments.