Final answer:
A closed-circuit breathing apparatus recycles the user's exhaled breath, removes carbon dioxide, and adds supplemental oxygen, allowing for extended use in environments where breathable air is not available.
Step-by-step explanation:
The type of breathing apparatus that recycles the user's exhaled breath by removing carbon dioxide and adding supplemental oxygen is known as a closed-circuit breathing apparatus. This system is commonly used by scuba divers, astronauts, and firefighters in environments where breathable air is either not available or limited. Unlike open-circuit systems, which release exhaled air into the surrounding environment, closed-circuit systems reuse the exhaled air after purifying it, thus conserving oxygen and allowing for longer durations of use.