Divemasters Should Ask 'Is Your Oxygen ON?'

[Scraps]

Have heard stories of DiveMASTERs tweaking other people's dive kit. I take an exceedingly dim view of people interfering with my kit.

Rebreathers are designed to kill you in multifarious ways. Failing to turn on oxygen is one example, but the real problem is not monitoring your PPO2 whilst ignoring all the warnings and then failing to recover from that in the many options available -- adding diluent, turning on the O2, diluent flush, bailing out...

The one thing "have you turned on your oxygen" is nowhere near as important as asking "have you turned your diluent on" as that affects your buoyancy and ability to breathe as you descend.


The simple mantra for a non-rebreather person is to ask to see the diver check the wing inflate (which implies checking the diluent's on) and that the PPO2 is above 0.7 prior to jumping (which implies all's well with the O2 side).

Car park attendant to customer: have you got enough fuel sir?

Now that is a constructive response. Better questions to ask. Thank you.

 

[Wookie]

Having been a premier tech diving liveaboard, I found it to my advantage to hire a diving safety officer to oversee the crew. He (or she) kept their eye on the divers and their dive planning as well, but really they were there to ensure that the crew remembered all of the things that come automatically for OC Divemasters, but are a learned behavior for CC divers, like watching the pre-breath, checking the positive and negative loop test, making sure to ask if O2 and Dil are charged and on, making sure cells agreed, all of the little things that can cause a disaster. Tech diving can be inherently disastrous on its own without adding shortcuts and dumb mistakes….

 

[Wibble]

I'm seriously asking for information now. Why does @DiveGearExpress's suggestion seem so onerous to you? Are you so in the zone that a casual exchange will throw you off the game? Is it like asking Tiger Woods a question in the middle of his backswing? Why does such a seemingly innocuous suggestion provoke such a reaction?

The real challenge is that rebreathers are a lot more complex than open circuit. It starts at least the day before when you build your unit; did you fully follow the checklist for the hour plus process? Everything from analysing your gas, filling scrubber, checking cells, checking batteries, positive and negative checks, making sure the unit's built correctly, checking the gases are programmed in correctly, etc.

The pre-dive checks take ~10 mins and include checking that all's plugged in, all's turned on, you can breathe, the computers are working, then a 5 minute pre-breathe which will validate the scrubber and that you're not "feeling funny". Basically chill before jumping.

The real things to check on a rebreather diver is pretty much the same as for OC: is the drysuit connected, gloves, hood, mask, stages, cannister torch, any nefarious dangly bits...

It is extremely good practice for the rebreather diver to stand at the gate and puff some gas in the wing and properly look at the PPO2 on the wrist-mounted computer in a way that other people can see that this check has been done:

• Will I float?
• Can I breathe?

Everything else can be dealt with on or under the water.



A quick point about OC divers. Tech OC divers** differ from recreational divers*** in that they've got the ability to resolve gas issues by themselves. The classic DiveMaster person is trained to look after the recreational divers who are frequently novices. In fact DiveMasters have to assume they're novices unless otherwise ascertained.

The rebreather 'knee-jerk reaction' is about the fact that rebreather divers would have put in a lot of training to work around the complexity of the unit. These aren't novice OW divers, but people who've got a demonstrable degree of skills. The classic DiveMaster has none of those skills (assume we're talking about your run-of-the-mill OC DM here). Whilst being concerned that the oxygen is switched on is a nice thing, it is just one of many many things that can go wrong on a rebreather.


** meaning diving with a twinset / sidemount and having practiced shutdowns and the like
*** meaning diving with a single BCD where your reserve is someone else's octopus

 

[Scraps]

Wibble,

Thanks for the thorough reply.

I've dove with buddies who were using rebreathers and have been shown a few of the steps you discuss.

I agree that a DM's skill set--even on the boats I work where nearly all the DM's are also instructors--is mostly focused on keeping inexperienced divers from killing themselves or getting lost.

We all know not to mess with gear brought on board by people who look like they know what they're doing.

People with rental gear or who don't look like they know what they're doing will get closer supervision and assistance as needed.

Anyone with a regular single-tank recreational setup will get a bladder squeeze and a tank valve check as they approach the debarkation point.

Anyone with tech gear (< 1% of customers) will get a polite request to verify they've done all their checks.

Any reason a CCR user couldn't be treated the same as a doubles or sidemount diver?

 

[NothingClever]

Car park attendant to customer: have you got enough fuel sir?

I didn’t get that at all from DGX’s friendly PSA.

 

[Wibble]

Anyone with tech gear (< 1% of customers) will get a polite request to verify they've done all their checks.

Any reason a CCR user couldn't be treated the same as a doubles or sidemount diver?

You should see that a 'tech' person has done their checks as they went through their kitting up process. Breathing from their primary and secondary at least three times; checking gas pressure(s); checking the longhose; inflating their wing; checking torches, etc.

The challenge with rebreathers is they're an order of magnitude more complex than OC. This should imply that they're more experienced and suitably qualified. The real issue with a rebreather, the tell, is if they're rushed or distracted. That's when things get left off; drysuit hose... Hopefully they'll be sufficiently aware to do their checks.

But nobody really minds if someone's got their best interests at heart. All about respect for each other.

Anyone with a regular single-tank recreational setup will get a bladder squeeze

No peeing in the water

 

[jadairiii]

DM: Sir, is that new absorbent in your scrubber or is it a year old and you keep drying it in your oven?

 

[rjack321]

I just got back from a week long CCR liveaboard. The skipper or the DM was pretty much on deck and watching us with our prebreathes on every dive. They didnt ask this exact question but I know they were watching me go, mav, mav, gauge, gauge, handset, hud, suit, wing.

Why do I know? Partway through that on one dive the skipper said "how about we unclip this secondary?" which was still attached to my loop hose - it belongs on my wrist. I would have discovered it in less than a minute but he was on top of it.

Saying dil is a more critical thing than O2 is incorrect. Dil being off would severely limit my buoyancy options and force me to use my suit only. But I couldnt breath 12/65 if dil was on and O2 was off. The first time the ADV fired as the loop volume declined I'd probably lose consciousness (if O2 was off). Divers are dying right now with their O2 off at about 100x the rate of divers not having dil. So "is your O2 on?" is a totally reasonable question to ask in an effort to address this risk.

Just wait a moment to break into my sequence - which is over by the time I am standing on the deck seconds away from giant striding. I may struggle to reach my O2 valve with the BO in the way standing though (and dry glove rings etc), so asking right before standing up would work better for me.

I don't mind being watched or queried.

 

[mderrick]

Arguing that a simple question prior to jumping is redundant might seem reasonable, but there are quite a few paths to jumping with the O2 off. The most common reason I have observed is the diver performs the pre-dive checks on their rebreather and then closes their valves; an ingrained habit among experienced open-circuit divers. I also see it happen when the diver doffs their gear after the first dive, habitually closes valves and fails to check before the second. Running the checks, then closing the valves is one path but roll-off with benches not setup for CCR is another reason I've personally experienced and also observed in others.

As with open-circuit, every CCR diver is trained to run their checklist and while there are certainly plenty of things that can go wrong... the most common item I notice in rebreather accident analysis is their O2 is off. Perhaps the reason jumping with O2 or electronics off is so consistently deadly is that with the task loading of entry and descent, the diver may not notice until it's too late. Fact is, jumping with O2 or electronics off happens and it is deadly and a simple question at the dive platform can save lives..

The hostility expressed in this thread by some over a simple question reminds me of the hostility sometimes directed at me when teaching highly experienced technical open-circuit divers regarding the use of rebreather checklists. If a cross-check has some negative implication regarding your skills, please ignore the annoying fellow at the dive platform who is just helping those new rebreather divers.

 

[Marie13]

Whether you agree with the use of Vindicator knobs or not, this was interesting. From DGX: