Rebreather World - View Single Post - Incident on the surface

brockbr · 26th March 2008, 15:45

I've been asked about my HUD, so I wanted to respond to that:

I do have a C2R HUD on my Classic KISS. This HUD uses 2 LED's. Green for pO2, and red for Decompression.

Green Slow Flash = Low pO2 (.2 or more under set point)
Green Solid - Within .2 of set point (high or low)
Green Fast Flash = High pO2 (.2 or more over set point)

Red relates only to deco and stops.

I generally run with a 1.0 set point. This means that on entry to the water, it is difficult to get a 1.0 at the surface, and for the first 3m or so. This means the LED is flashing Green Slow on initial entry.

The VR3 supports multiple set points, and I started out by diving a .7/1.0. But even a .7 suffers from the same problem - Hard to maintain .7 at the surface, so either way, the indications is a Green Slow Flash. This really serves as a reminder to check, check, check your pO2.

Prior to putting my head under, I would flush with Dil so I didn't enter the water with a high pO2 in my loop that I can't burn off fast enough, thus spiking my pO2 on decent. To illustrate this, if I started with a true .5 or higher, an immediate decent to depth will easily spike the pO2.

Also, in getting ready to do CCR Trimix, I've read this step is especially import so that the gas mix is correct in your loop, and not some weird mix of air + dil, which could make your N2 higher then your Dil.

At any rate, the Green Slow Flash is "normal" on entry, but more importantly, it is the ONLY warning of a low pO2 - Nothing secondary after that.

In my case, I am usually very diligent about watching my pO2, and my HUD was doing exactly what it should have. Had I sat on the surface resting, my pO2 would probably have climbed slowly. As it was, I was swimming quickly, which caused the high consumption (this was where I made the mistake - I didn't account for needing to check my pO2 even more often if I was on the loop at all!).

HUDs are great tools, but to paraphrase Dave Sutton who recently said "given all the right tools, the diver can still kill themselves" - Vigilance is the only way.

26th March 2008, 15:45	#20 (permalink)
brockbr Train Wrecked ;) Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Dec 2007 Location: Alabaster, AL Posts: 223	Re: Incident on the surface - mCCR I've been asked about my HUD, so I wanted to respond to that: I do have a C2R HUD on my Classic KISS. This HUD uses 2 LED's. Green for pO2, and red for Decompression. Green Slow Flash = Low pO2 (.2 or more under set point) Green Solid - Within .2 of set point (high or low) Green Fast Flash = High pO2 (.2 or more over set point) Red relates only to deco and stops. I generally run with a 1.0 set point. This means that on entry to the water, it is difficult to get a 1.0 at the surface, and for the first 3m or so. This means the LED is flashing Green Slow on initial entry. The VR3 supports multiple set points, and I started out by diving a .7/1.0. But even a .7 suffers from the same problem - Hard to maintain .7 at the surface, so either way, the indications is a Green Slow Flash. This really serves as a reminder to check, check, check your pO2. Prior to putting my head under, I would flush with Dil so I didn't enter the water with a high pO2 in my loop that I can't burn off fast enough, thus spiking my pO2 on decent. To illustrate this, if I started with a true .5 or higher, an immediate decent to depth will easily spike the pO2. Also, in getting ready to do CCR Trimix, I've read this step is especially import so that the gas mix is correct in your loop, and not some weird mix of air + dil, which could make your N2 higher then your Dil. At any rate, the Green Slow Flash is "normal" on entry, but more importantly, it is the ONLY warning of a low pO2 - Nothing secondary after that. In my case, I am usually very diligent about watching my pO2, and my HUD was doing exactly what it should have. Had I sat on the surface resting, my pO2 would probably have climbed slowly. As it was, I was swimming quickly, which caused the high consumption (this was where I made the mistake - I didn't account for needing to check my pO2 even more often if I was on the loop at all!). HUDs are great tools, but to paraphrase Dave Sutton who recently said "given all the right tools, the diver can still kill themselves" - Vigilance is the only way.
(Offline)