They recirculate exhaled gas, scrub CO2 with soda lime, and inject O2. mCCR fixed flow, eCCR adjusts in real time. Mandatory pre-dive check: watertightness, 3 O2 cells, scrubber, alarms. Divesoft, rEvo, JJ-CCR.
The rebreather community debates the choice between different models (Kiss, AP Diving, rEvo, JJ-CCR, Mares Horizon), their real maintenance costs, and the lifespan of soda lime. Safety notices about defective oxygen sensors are recurring and cause concern. Discussions cover cleaning and disinfecting the unit, the difference between axial and radial scrubbers, and when to transition from open circuit to a rebreather.
The basic principle consists of recirculating exhaled gas, removing CO₂ via soda lime, and injecting oxygen to maintain the partial pressure of O₂ between 1.0 and 1.3 bar. mCCRs inject a fixed oxygen flow, while eCCRs use O₂ cells to adjust injection in real time. Most serious incidents are related to skipping the pre-dive check, a poorly packed scrubber, or out-of-calibration cells. The pre-dive protocol includes at minimum: leak test, verification of all three O₂ cells, absorbent check, and alarm test.