PSA: drill your internal booms

[KBlack]

Lift head - vent out of sides of mouth while shutting down both valves
Once closed check PO2 for high - indicating O2 boom / low indicating diluent boom
Once buoyancy controlled bail out to bottom gas for "Time Out " catch your breath and signal buddies if they are not already aware from the noise.
Confirm by checking gauges and diagnose problem.
Return to loop when comfortable if PO2 within breathable range. Dill flush as required.

 

[mr_v]

That is exactly what he did... and wound up on the surface. Don't you think it's better to vent AND crank on the valve -- simultaneously? Without venting, you're definitely going up and gaining speed.

You mentioned that the buddy is relatively new to CCR diving, so there may have been other variables involved. But yeah, if there is a substantial amount of extra volume in the loop, you'd vent while shutting the valves. However, venting the loop should not require any significant effort, kicking, etc.

 

[Heat Miser]

thanks for sharing .... I havent had an internal boom, (well I have had a solenoid fail closed but not a dangerous one like you describe, especially imagine if it was O2) ... however if it ever happens I hope I see it quickly. It is the main reason I manually run the unit in parachute mode i.e. dont rely on the the solenoid. So I have the solenoid setpoint set 0.2 below actual setpoint, so hopefully it forces you to see the booms coming faster.

Other people I know swear by a Nerd, but I have never used one.

 

[inquis]

You mentioned that the buddy is relatively new to CCR diving, so there may have been other variables involved.

Excellent point, and I suspect that may have contributed largely. The chief thing that struck me was he didn't vent out his mouth in spite of the *significant* pressure; only intentional nose exhales. Not an aggressive/effective mouth exhale, and certainly not a passive "relax/open the airway and let it flow as fast as it wants". That's part of why I want to drill this myself -- to somewhat put myself in his shoes, so to speak.

 

[inquis]

Other people I know swear by a Nerd, but I have never used one.

I use one, and it's extremely quick to indicate high PO2 (as well as quite obvious). It's not uncommon for it to briefly flash red as the "slug" of O2 moves past the sensors after a manual addition before falling back down.

I have mine on the side of my non-dominant eye, and can somewhat "see through" it when looking at the terrain/etc. It's pretty cool how the brain fuses the signals.

 

[Rebreather Rabbit]

My dive buddy and I routinely practice 'playing tricks' with each other after clearing deco at a local inland site to keep skills fresh. The #1 thing we do is hit and hold our buddy's ADV until they shut down the Dil tank.

Just like this scenario, gas volume addition is FAST and requires a quick and proper response to avoid popping out of the water.

 

[inquis]

Oooo, the SABR move -- "sneak attack by Rabbit". I like it.

 

[lizardland]

Other people I know swear by a Nerd, but I have never used one.

I use a Hammerhead DIVA on my Mk15 and it has the added feature of rattling the teeth out of your head. It's physically uncomfortable when it triggers. I really like it. Simple red/amber/green flashing light doesn't take any brain power either. Most of the time I dive just from the DIVA with sanity checks on the secondary. It's great.

 

[bipolarbear]

Runaway ADV, leaky MAVs or a stuck open solenoid are one of the more serious issuers we can face while rebreather diving.

In my training, I was taught to aggressively vent while shutting off the valves. 02 can be closed quickly because I only run that open 4 half turns.

Having moved past my initial training, I think that in the event of unexplained gas dumping into my loop, my response on my unit (JJ) would be:

1. Immediately vent (hard), while going into a position in which I can dump my loop volume (which is on the right, right next to where my 02 valve is).
2. Close the 02 valve (this should take only a couple of seconds).
3. If gas is still entering the loop, then instead of messing around with the dil valve (often times with rental tanks I've found this can sometimes take 20 half turns), I would just close the flow stop and disconnect the dil MAV. Those steps should take 2 seconds.
4. At that point, depending on my P02 and loop volume, I might come off the loop while I sort out what has happened.

I'm not looking forward to the day I have to execute this plan...

 

[J-Vo]

Oooo, the SABR move -- "sneak attack by Rabbit". I like it.

This response makes me quite glad I don't have an ADV.