Are Rebreathers dangerous for SCUBA diving?

What are the dangers of using these things?

Rebreathers, whether semi-closed or fully closed circuit, are just another form of SCUBA gear. The ‘recreational’ rebreathers on the market today are designed with multiple redundancy (sensors, gauges, etc.), so a failure of one component should not render the unit completely unusable. As with all SCUBA gear, the main danger in use comes from user error.

Such errors can include: failing to set up the unit correctly, failing to conduct adequate ‘pre-flight’ safety checks, failure to monitor gauges during the dive, or disregarding guage information, failure to adequately plan the dive (‘diving the computer’), or attempting overly ambitious dives before gaining sufficient experience on ‘easy’ dives.

Specific examples (by no means an exhaustive list) are:
Failure to replace the CO2 scrubber as often as necessary, leading to CO2 buildup, feelings of suffocation, hyperventilation and panic.
Failure to replace batteries, resulting in sensor/solenoid failure
Failure to turn on the O2 supply, leading to sudden unconsciousness when the breathing-loop pO2 drops below about 0.12 bar
Failure to turn on the diluent, resulting in uncontrolled descents
Skipping pre-dive checks, thus failing to notice gear setup errors
Failure to monitor pO2 at depth, leading to O2 toxicity
Diving while inequipped/unable to make an emergency ascent (including deco stops)

Adhering to basic training principles, and applying the precautionary principle (“If in doubt, bail out”) go a long way towards keeping the rebreather diver safe underwater.

Silent Diving – Diving Rebreathers

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