In various hazardous situations, which type of SCBA allows for longer working durations?

The type of Self-Contained Breathing Apparatus (SCBA) that allows for longer working durations in hazardous situations is the closed-circuit SCBA. Closed-circuit SCBAs recycle exhaled air, removing carbon dioxide and replenishing oxygen, thereby extending the usable time when compared to open-circuit systems that release the exhaled air into the atmosphere.

In contrast, open-circuit SCBAs operate by taking in fresh air from a tank and expelling the exhaled air, leading to a finite supply limited by the tank's capacity. While high-efficiency filters are useful for specific particulate protections, they do not offer the same breathable duration in hazardous environments as a closed-circuit system. Conventional masks, while effective for certain applications, typically do not provide the same level of protection or duration as a properly functioning closed-circuit SCBA in situations involving toxic gases or other hazardous atmospheres. Thus, the closed-circuit system is designed to enhance duration and safety for users in prolonged exposure scenarios.