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Products Rebreathers What is a Rebreather
Products Rebreathers What is a Rebreather
What is a Rebreather
RMS TEC are Asia's Rebreather specialist 'one stop shop' for all AP Diving Rebreathers (CCRs) including the Evolution, Evolution+, Inspiration, Inspiration Classic, Accessories, Spares and associated diving products supported with the best Rebreather and Technical Diving training available in the Asia Pacific Region.
Closed Circuit Rebreathers (CCRs)
In contrast to conventional scuba or open circuit where most of the breathing gas is wasted on exhalation into the surrounding water, APD rebreathers are all fully closed circuit systems in which all of the exhaled breath is retained within a closed loop.
It is then filtered and refreshed and recycled back to the diver for further use, giving the ultimate endurance of any breathing apparatus.
Only during ascent and mask clearing are bubbles emitted.
1. Exhaled breath leaves the diver’s lungs and is directed into a one-way
loop or closed circuit starting at the unit’s exhale counterlung.
2. It then travels, via a water-trap, over the right shoulder into the scrubber
unit where it passes upwards through a chemical (Sofnolime) filter stack.
This effectively scrubs the breathing gas of carbon dioxide.
3. Inside the mixing chamber, three independent oxygen sensors measure the
oxygen pressure, the PO2, of the mix. If the PO2 drops (due to the diver’s
metabolism or due to ascending) below a predetermined target level called the
PO2 setpoint the oxygen controller opens an oxygen valve or solenoid bringing the
PO2 back up to the setpoint – a very simple system.
4. Scrubbed and refreshed the breathing gas returns via another water-trap to
the inhale counterlung ready for use in the next cycle.
There are two onboard cylinders (3 litres on the Inspiration, 2 litres on the Evolution). One contains pure Oxygen, the other a diluent Gas - usually Air.
NOTE: If Trimix / Heliox is used instead of air as the diluent supply and modification is made to the bailout contingency, both APD CCRs can be dived to depths of 100m. However, it must be stressed, such advanced closed circuit diving should only be carried out by suitably experienced divers who have achieved the appropriate advanced unit-specific CCR qualification with one of the recognised training agencies.
The diluent has several functions:
Closed Circuit Rebreathers (CCRs)
In contrast to conventional scuba or open circuit where most of the breathing gas is wasted on exhalation into the surrounding water, APD rebreathers are all fully closed circuit systems in which all of the exhaled breath is retained within a closed loop.
It is then filtered and refreshed and recycled back to the diver for further use, giving the ultimate endurance of any breathing apparatus.
Only during ascent and mask clearing are bubbles emitted.
1. Exhaled breath leaves the diver’s lungs and is directed into a one-way
loop or closed circuit starting at the unit’s exhale counterlung.
2. It then travels, via a water-trap, over the right shoulder into the scrubber
unit where it passes upwards through a chemical (Sofnolime) filter stack.
This effectively scrubs the breathing gas of carbon dioxide.
3. Inside the mixing chamber, three independent oxygen sensors measure the
oxygen pressure, the PO2, of the mix. If the PO2 drops (due to the diver’s
metabolism or due to ascending) below a predetermined target level called the
PO2 setpoint the oxygen controller opens an oxygen valve or solenoid bringing the
PO2 back up to the setpoint – a very simple system.
4. Scrubbed and refreshed the breathing gas returns via another water-trap to
the inhale counterlung ready for use in the next cycle.
There are two onboard cylinders (3 litres on the Inspiration, 2 litres on the Evolution). One contains pure Oxygen, the other a diluent Gas - usually Air.
NOTE: If Trimix / Heliox is used instead of air as the diluent supply and modification is made to the bailout contingency, both APD CCRs can be dived to depths of 100m. However, it must be stressed, such advanced closed circuit diving should only be carried out by suitably experienced divers who have achieved the appropriate advanced unit-specific CCR qualification with one of the recognised training agencies.
The diluent has several functions:
- Automatically injected into the inhale counterlung by the ADV (Auto Diluent addition Valve) on descent in order to maintain counterlung volume (or manually injected by the diver if no ADV is fitted). It is also used for BCD and dry-suit inflation. Only small quantities are used – typically 30-40 bar per dive.
- As a ‘diluent’ or dilutant it dilutes the gas mix so that it is safe to breathe at depths greater than 6m.
- The third and extremely important function is that it provides a reserve gas supply for either a ‘diluent flush’ or open circuit bailout if needed. (See Safety & Bailout)
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