Causes of needing to bail out analysis

[RedSeaDiver2]

I am someone that much prefers to use a fullface mask when diving a rebreather.

I'm currently doing a bit of a risk analysis of what are the potential situations/causes that would require a diver who is diving to normoxic trimix depths to have a situation where they have to bailout to something other than a BOV (on a fullface mask) - in other words they would have to remove their fullface mask and then use a normal second stage on their bailout and then fit a normal dive mask.

A bad caustic cocktail is one such situation, what other situations / emergencies can anyone think of?

 

[rjack321]

Flood / caustic the worst kind of failure.
CO2 hit and overbreathing the so-so BOV
Failure of the BOV diaphram or exhaust valve
Loss of dil/suit gas requiring you to manually inflate your wing

 

[RedSeaDiver2]

Flood / caustic the worst kind of failure.
CO2 hit and overbreathing the so-so BOV
Failure of the BOV diaphram or exhaust valve
Loss of dil/suit gas requiring you to manually inflate your wing

Fortunately the BOV is Apeks-based so should be OK - I'm not sure what model of Apeks though - but probably as good as the Apeks I would be bailing to.

BOV failure would definitely be something to guard against - good point!

Many years ago there was a diver in NJ couldn't get off the bottom due to incompatible connectors etc - I think it was after bailing off the CCR - it is something that I have always kept in the back of my mind as a lesson to learn from.

 

[rjack321]

Fortunately the BOV is Apeks-based so should be OK - I'm not sure what model of Apeks though - but probably as good as the Apeks I would be bailing to.

The shrimp does not breath that great at depth. I have one and have bailed at 200ft on it. It's a very simple 2nd stage. Do not skimp on your helium in the BO.

 

[inquis]

The shrimp does not breath that great at depth.

I've heard there are 2 versions of the shrimp, with noticeable better WOB in the second. Is your observation from the original or updated version? I've practiced BOs from 150 ft without noticing any issue, but the density was only 4.5 g/L at that depth (and normal breathing rate, being a drill).

 

[rjack321]

I've heard there are 2 versions of the shrimp, with noticeable better WOB in the second. Is your observation from the original or updated version? I've practiced BOs from 150 ft without noticing any issue, but the density was only 4.5 g/L at that depth (and normal breathing rate, being a drill).

My understanding was the flapper valves changed from v1 to v2 to improve the CC WOB. Not anything on the OC side. But I only recall that from a very old statement by Jakob

 

[RedSeaDiver2]

The shrimp does not breath that great at depth. I have one and have bailed at 200ft on it. It's a very simple 2nd stage. Do not skimp on your helium in the BO.

Bottom bailout at 60 metres is 18/40

 

[grantctobin]

Bottom bailout at 60 metres is 18/40

Answer is really just not using an FFM for this style of dives. If you insist on it and continue to use a BOV, might want to switch to something with beefier helium.

 

[RedSeaDiver2]

Answer is really just not using an FFM for this style of dives. If you insist on it and continue to use a BOV, might want to switch to something with beefier helium.

Sorry I should have clarified - the initial bailout will be to the 18/60 in the 3 litre on my back, then to 12 litre 18/40 and so forth.

 

[grantctobin]

Sorry I should have clarified - the initial bailout will be to the 18/60 in the 3 litre on my back, then to 12 litre 18/40 and so forth.

I don’t know how often this needs to be said in order for people to realize it. A BOV into a 3L is insufficient if you were to ever find yourself in a CO2 hit. I’d give it a…25%? chance someone with a severe hit with a full face mask plugged into a 3L (even if a full one, which it won’t be) could survive the consequences of that to be able to bail out, then deal w the extra nonsense to get a different mouthpiece or pod into their mouth at 60M.