Hi all,
I am trying to understand in detail the sequence of pre-breathing actions and their reason. Acknowledging that pre-breathing has been proven ineffective for hypercapnia prevention (article from @Dr Simon Mitchell in 2015; also discussed at length here Does Pre-breathing Your Rebreather Matter?), I have tried to understand the procedure recommended by Edd Sorenson ():
By doing this you
I am trying to understand in detail the sequence of pre-breathing actions and their reason. Acknowledging that pre-breathing has been proven ineffective for hypercapnia prevention (article from @Dr Simon Mitchell in 2015; also discussed at length here Does Pre-breathing Your Rebreather Matter?), I have tried to understand the procedure recommended by Edd Sorenson ():
- After building the rebreather do a positive on pure O2: you have 100% O2 in the loop as you have just calibrated the sensors; you go to the dive site with pure O2
- Before geting in the water turn OFF the oxygen and ON the dil — Breathing 3 times from the loop and exhaling from the nose (not in the loop) should bring the ppO2 down to that of the dil (e.g., 0.32 on 32/00) as the ADV is compensating the mix lost at every breath by adding diluent
- Turn the O2 ON take 3 breaths exhaling from the nose and check that O2 is raising to the set point (e.g., 0.7) as the solenoid is now able to inject O2
By doing this you
- Check calibration of sensors on O2 (Steps 1 and 2)
- Analyse the dil (Step 2)
- Verify that the dil is added correctly by the (Step 2)
- Verify that the O2 is added correctly (Step 3)