rebreather

A rebreather is a breathing apparatus that recycles exhaled gas by removing carbon dioxide and adjusting the gas mixture for the user. Instead of venting exhaled gas as bubbles, a rebreather scrubbers the CO2 from the loop and replenishes oxygen or diluent to maintain a breathable mixture. Rebreathers are used in underwater diving, aviation, medicine, and certain industrial applications.

There are two main types used in diving: closed-circuit rebreathers (CCR) and semi-closed circuit rebreathers (SCR). A CCR continuously adds oxygen and, if needed, diluent gas to maintain a target partial pressure of oxygen (PPO2) for the diver’s depth, while recirculating and scrubbing the loop gas. SCRs replace a portion of the exhaled gas with fresh gas in a fixed ratio, reducing gas consumption but offering less precise control of oxygen levels. Both rely on a carbon dioxide scrubber, commonly containing soda lime or similar material, and onboard sensors to monitor gas composition.

Advantages of rebreathers include greatly extended gas supply, reduced buoyancy loss from gas expansion, and reduced bubble production for stealth or scientific work. Disadvantages include greater mechanical complexity, greater skill and maintenance requirements, dependence on scrubber integrity, and risks such as CO2 buildup, oxygen toxicity, or equipment failure if not properly operated.

Safety and training are essential. Users require specialized instruction, regular maintenance, and checks before each use. In medical settings, rebreathing systems are part of anesthesia equipment, circulating anesthetic gases and removing CO2. In other industries, they serve niche roles where efficiency and gas conservation are important.