Always know your ppO2 !

lizardland

If you have a Rebreather with an ADV then a flush means breathing the loop volume down far enough to get the ADV to fire. That means breathing down a gas that might be hypo/hyperoxic. It may only be one breath but that's all it takes.

__________________
Can you imagine drifting along in the sea with your mouth open and a load of f***ing plankton going in? You'd like it, would you?

www.westons-cider.co.uk

Azerbaijani Association of Technical Divers Publicity Officer and Goat Wrangler

Joe

Not really.

First, I agree that getting off the loop and taking a sanity breath is clearly the safest option and would be my first choice....but....at least with OTS CL's...you can open your CL exhaust valve, roll so the valve is up and dumping gas, exhale, empty the CL and flush with the ADV while holding your breath for a few seconds.

6Gill

Ahhh, to own a Meg, those of us with a CK have to suck it through the loop or use the opv (difficult without your buddy) but we do have that nice switch on the DSV.

ding

With the YBOD a dill flush is pressing the inflate on the left (inhale) lung and dump from the right lung. I also have offboard gas plumbed into the left lung I can use for a Dill flush so depending on depth I have a gas to flush with.

graham_hk

Phi - I can verify what Brian said.

koputai

No, that's a MAJOR design floor on the KISS. Most rebreathers have a button by which you can add dill manually in this situation.

Jason.

Steve

So does the KISS. A part turn of the DSV achieves the same thing.

__________________
WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.

AD_ward9

The diver could not use the manual add button: the dil had only 10% O2 in it. If the diver flushed he would have died faster.

However, this accident was not caused by using a hypoxic dil. To determine whether the hypoxic dil was in any way a cause of the accident, we ran the same profile using air. Air by definition is not hypoxic.

The diver still would have died. The plot is below.

O2 flush would have worked so long as the diver remembered to do it again and again. Better to bail out: going to the reg that was fitted to the O2 tank, or the reg on the 7ltr bail out the diver was carrying. One of DrMike's incidents illustrates how one can forget there is a 7ltr bail out cylinder on your clips, and DrMike had a long time to think about what to do. This diver had seconds.

Incidentally, on the subject of plots, if the user dives with the handsets switched off on the surface, breathing on the loop 30 seconds before they dive, they die after being in the water just 10 seconds, and the profile goes straight down. If they have a short swim to the shot, then failing to switch on the handsets will kill the diver even before the dive begins. On the other hand, if the unit is on with a PPO2 of 0.7 on the boat and then handsets stop due to the design errors in the battery box, electronics and software, as you roll off the boat, you die much later. Some deaths are put down to the user being so dumb they did not switch on the rebreather, when if the examiner was wise enough to run the profile it would be clear it must have been switched on on the surface, but the malfunction of the handsets underwater caused the diver to switch them on and off to try to restart them. Those software errors I mention mean that switching the beast on and off may not bring it back up, so you surface with the unit off. Examination of the contacts with a microscope can identify battery bounce immediately because of the arc erosion of the contacts. What I am saying, I am 99% sure that the diver in the case below is not the only one to have been killed by these design faults, and then failing to bail out: any death with the handsets found to be off on diver recovery but the diver managed more than a 30s underwater implies the unit was switched on when the dive started, though to be sure, it is necessary to run their exact profile. Shows also: check your handset is on and ticking just after you jump in. Checking into the dive is too late.

The biggest gift an instructor can give is to keep his student alive, when without that teaching, he would be dead. Practising bail out should be standard on every rebreather course, and please, use these graphs as an example of why it is so imperitive.

Attached Images

Screenshot-1.png (19.7 KB, 486 views)

koputai

Partly true Steve.
With a button you just keep on breathing as before (even if under duress), whereas with the DSV you have to consciously coordinate your breathing and switch timing to dump o/c gas into the loop. This may not be possible in a lot of situations.

Regards,
Jason.

graham_hk

If this is the case why can most people hold their breath (if forced) for 2mins? I think you are confusing hypoxia with death and it all sounds a bit dramatic to me - don't get me wrong I understand the importance of your message.

Furthermore, I wonder how these figures are calculated -since the last time I dived CCR (admitidly a year ago) I don't remember the PO2 falling 0.05 in 30 seconds.

Best, Graham