Checklists in Rebreather Diving
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OTF
Coney Island Whitefish Biologist
Prebreathes and checklists are two entirely separate topics.
It's more about the "very little gain" from a 5 minute prebreathe than the "time and discomfort". But yeah that time is a factor in the busy and often unfortunately rushed pre-dive preparation period. I would rather be fixing issues, re-checking things, or reviewing plans with my team in the time it takes to do a worthless prebreathe mumbling responses and drooling all over the deck.
What does that mini-prebreathe actually achieve? Beginning to prime/heat the sorb (true but not necessary, maybe valuable in actual arctic conditions?), checking that the unit can maintain a setpoint (covered by other checks), checking that the scrubber is working/catching breakthrough (not happening in 5 minutes). Being forced to sit there holding the handset and thinking about the dive might be truly valuable in that it gives you focused time to think, visualize, and triple check computer settings. But that's straying pretty far from the traditional purpose of a prebreathe.
If you're arguing that we should all commit to 15+ minute prebreathes that can actually catch scrubber issues, you wouldn't be wrong if safety really does come before all else. But damn that's a high bar to meet.
It's more about the "very little gain" from a 5 minute prebreathe than the "time and discomfort". But yeah that time is a factor in the busy and often unfortunately rushed pre-dive preparation period. I would rather be fixing issues, re-checking things, or reviewing plans with my team in the time it takes to do a worthless prebreathe mumbling responses and drooling all over the deck.
What does that mini-prebreathe actually achieve? Beginning to prime/heat the sorb (true but not necessary, maybe valuable in actual arctic conditions?), checking that the unit can maintain a setpoint (covered by other checks), checking that the scrubber is working/catching breakthrough (not happening in 5 minutes). Being forced to sit there holding the handset and thinking about the dive might be truly valuable in that it gives you focused time to think, visualize, and triple check computer settings. But that's straying pretty far from the traditional purpose of a prebreathe.
If you're arguing that we should all commit to 15+ minute prebreathes that can actually catch scrubber issues, you wouldn't be wrong if safety really does come before all else. But damn that's a high bar to meet.
kissonerga.ccr
Contributor
When is a checklist not a checklist?
We all agree that checklists are extremely important for task sequencing. Plenty of examples in the aviation and medical sectors, similarly with rebreathers. Wouldn’t be without them for the build and close phases. Amongst other things, it forces one to do things in the right order and prevents one from skipping critical steps. Furthermore they provide an audit log to compare previous builds and remember settings.
Longer and complex checklists are a no brainer.
What about shorter checklists, with few items. Can a mnemonic do the same aide memoir function as a checklist? This has been used forever in mathematics, "Should old Harry, catch a herring, trawling off America" (sine is opposite over hypotenuse, etc.). Used in other sports such as paragliding "Ha Ha Said The Clown" (helmet, harness, steering toggles, canopy). Used in diving too as in PADI's BWRAF (buoyancy, weights, releases, air, final check). GUE-EDGE too (long forgotten!). This proves that there are alternatives to physical checklists as long as it’s kept simple.
What about other validation techniques, such as counting or chanting. No doubt there’s many a military mnemonic screamed out by recruits — "stick it in, twist it, pull it out".
The point is that there’s many variations on the checklist principle. Long and complex tasks need a written checklist. Sully's famous engine restart following the double engine bird strike, where thankfully he changed the order to start the APU to earlier.
Shorter and less complex tasks suit mnemonics or chants. Such as the pre-jump checks:
Don’t Be Diving Off Poorly Prepared
We all agree that checklists are extremely important for task sequencing. Plenty of examples in the aviation and medical sectors, similarly with rebreathers. Wouldn’t be without them for the build and close phases. Amongst other things, it forces one to do things in the right order and prevents one from skipping critical steps. Furthermore they provide an audit log to compare previous builds and remember settings.
Longer and complex checklists are a no brainer.
What about shorter checklists, with few items. Can a mnemonic do the same aide memoir function as a checklist? This has been used forever in mathematics, "Should old Harry, catch a herring, trawling off America" (sine is opposite over hypotenuse, etc.). Used in other sports such as paragliding "Ha Ha Said The Clown" (helmet, harness, steering toggles, canopy). Used in diving too as in PADI's BWRAF (buoyancy, weights, releases, air, final check). GUE-EDGE too (long forgotten!). This proves that there are alternatives to physical checklists as long as it’s kept simple.
What about other validation techniques, such as counting or chanting. No doubt there’s many a military mnemonic screamed out by recruits — "stick it in, twist it, pull it out".
The point is that there’s many variations on the checklist principle. Long and complex tasks need a written checklist. Sully's famous engine restart following the double engine bird strike, where thankfully he changed the order to start the APU to earlier.
Shorter and less complex tasks suit mnemonics or chants. Such as the pre-jump checks:
Don’t Be Diving Off Poorly Prepared
- Drysuit
- BCD
- Diluent
- Oxygen
- Pressures
- PPO2
AP made now stickers with an assembly checklist and pre-dive checks. You can stick them were you want. I have seen that people stick them on a table where they prepare the unit, on the unit itself, on the scrubber pot, etc.
A checklist can be wetnotes, but a checklist can also be a sticker, a paper with it on, etc. But use what works for you. I personnally don't use wetnotes for a checklist, I use them only in a 'discussion situation' under water, a backuplan is written in the wetnotes, and it is a way to talk to buddies).
But also important for me to build my unit together is 'me-time', nobody that distracts me. If someome asks me about the unit, I will explain, but in the way I do the assembly, not start with explaining the last part you have to build together, but what has to be done first, explain that first.
A checklist can be wetnotes, but a checklist can also be a sticker, a paper with it on, etc. But use what works for you. I personnally don't use wetnotes for a checklist, I use them only in a 'discussion situation' under water, a backuplan is written in the wetnotes, and it is a way to talk to buddies).
But also important for me to build my unit together is 'me-time', nobody that distracts me. If someome asks me about the unit, I will explain, but in the way I do the assembly, not start with explaining the last part you have to build together, but what has to be done first, explain that first.
What are are those? How do you know that the unit can maintain SP without breathing it.
IMHO there is not downside to breathing for 5 min. Claiming time is the issue sounds silly. I don't mean to attack you but it sounds ridiculous to me when you call a pre breath 'worthless' and other people calling it BS.
We know for a fact that people have died because they skipped checks. How is not breathing not skipping a safety check?
I can flush the loop and see the 02 rising without breathing but while breathing is see it more than once.
I already answered that. A number of people would still be around had they pre breathed their unit and didn't rush into the water.
J-Vo
Contributor
I never expect my unit to "maintain the setpoint", I maintain the setpoint.
billgraham
Contributor
However you remember it that works for you! By pressures, do you mean the positive and negative tests, or looking at the gauges when you turn the tank valves on? I think not doing the positive and negative tests properly have been the reason for a number of floods I have seen (including my own!)
Oxygen and diluent pressures— proves they’re turned on after using the inflates.
(I have AI transmitters installed on my rebreather, displayed on the Nerd, so it’s in the eyeline)
billgraham
Contributor
Ya, in the Ted McCoy 2's thing, you start with the two tank valves, then the pressure gauges, etc. Where I left off, I dove a sidemount CCR that I'd set up right before the dive and do the positive and negative tests right then. At one point, I had loop hoses that threaded into the head with collars. The first time I dove it was on a rolling boat, and I managed to misthread a loop hose in such a way that it passed my (probably lame ) + and -, and then flooded at depth. The takeaway is if you have loop hoses with threaded collars, pull in and out on the fitting after you have it screwed down to make sure it doesn't move.
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