Full face during deco.

[chevv58]

I've read that some NAVY and Commercial divers will actually deco on 100% O2 at depths deeper than 20 fsw. Now they are usually wearing hard helmets and wouldn't have to worry about the O2 toxicity effects. I mean, convulsions aren't fun. But in a helmet, you probably aren't gonna drown.

I know most tech divers, are against full face masks during a dive, and I agree. But, to aid in decompression for whatever reasons (I haven't done the math yet), what could the possible drawbacks be of full face mask decompression (when decompressing with O2, below 20 fsw) with a mask that doesn't "lock" the reg in (like the Scubapro model), but the kind where the reg simply is slid in and held by only the molded rubber of the mask?

Just looking for some opinions here.

 

[Jason Ooi]

Are you tech diver?
Specify full face mask air switching for tech diver consume 100 O2 at 6m 50% at 21m.
You must have a proper training before use it.

 

[Cave Diver]

 

[DA Aquamaster]

Unless things have changed greatly, Navy and commercial divers doing non saturation deco dives will do deco stops to 40 feet in water and then get pulled to the surface stuffed in a chamber and blown back down. They then will do deco in the chamber on 100% O2 while holding the mask to their face and with an attendant present. If they feel signs of an oxtox hit coming on, they remove the mask, if they get no signs and convulse, the mask falls away by itself and the attendant is there.

It's a long way from doing deco in water with 100% 02 at partial pressures greater than 1.6. If you convulsed in a full face mask at depth, you would need to reduce the partial pressure and that would require either an ascent or a switch in gases. A gas block would be an option, but you'd still need someone else to switch it.

Changing regs in the mask is a non starter as even with amask designed for that, it takes a responsive diver to know when not to inhale and to clear the mask after the switch.

Switching to a gas with too high of an O2 content is already one of, if not the, top killer of tech divers, so why make it worse? At best on the average moderate deco tech dive, you'd only save a few minutes of deco going on O2 at 30 ft instead of 20 ft and it is not worth the risk or complexity.

 

[chevv58]

Jason:

if you're asking if I've had Technical Training, yes. I've completed TDI Advanced Nitrox, Deco Procedures, and Intro to Cave. However, I've only recently finished Deco Procedures and have yet to make it part of my regular diving. Also, I'm having a little trouble using the Scubaboard profile edit, I have more than 16-50 logged dive. ha!

DA Aquamaster:
The only reason I mention the non-regulator locking mask, is not beacause you'd be switching out regs in a mask, but just to have in case you NEED to give up your deco reg, for some reason or another. I picture the arrangement being as such; just having the full face bungeed to your deco bottle with it's own reg and everything all set to go. When it's time to deco, just switch masks and clear. But, once again, I haven't done the math on this yet. You're probably right, starting deco at 50' or 60' on 100% O2 may only make minutes of a difference in total deco time, and would then, of course, not be worth the added risk and complexity. I'm just looking for some opinions.

 

[karstdvr]

Unless things have changed greatly, Navy and commercial divers doing non saturation deco dives will do deco stops to 40 feet in water and then get pulled to the surface stuffed in a chamber and blown back down. They then will do deco in the chamber on 100% O2 while holding the mask to their face and with an attendant present. If they feel signs of an oxtox hit coming on, they remove the mask, if they get no signs and convulse, the mask falls away by itself and the attendant is there.

It's a long way from doing deco in water with 100% 02 at partial pressures greater than 1.6. If you convulsed in a full face mask at depth, you would need to reduce the partial pressure and that would require either an ascent or a switch in gases. A gas block would be an option, but you'd still need someone else to switch it.

Changing regs in the mask is a non starter as even with amask designed for that, it takes a responsive diver to know when not to inhale and to clear the mask after the switch.

Switching to a gas with too high of an O2 content is already one of, if not the, top killer of tech divers, so why make it worse? At best on the average moderate deco tech dive, you'd only save a few minutes of deco going on O2 at 30 ft instead of 20 ft and it is not worth the risk or complexity.

Good advice.

Personally when I have 2 stages or more,my 50/50 bottle,and have my O2 bottle;I don't want to deal with trying to put on a full face mask,this is an invitation to Murphy.

I will stick with the tried and true,O2 at 20' with air breaks at intervals.

 

[Mr.X]

Jason:

if you're asking if I've had Technical Training, yes. I've completed TDI Advanced Nitrox, Deco Procedures, and Intro to Cave. However, I've only recently finished Deco Procedures and have yet to make it part of my regular diving. Also, I'm having a little trouble using the Scubaboard profile edit, I have more than 16-50 logged dive. ha!

DA Aquamaster:
The only reason I mention the non-regulator locking mask, is not beacause you'd be switching out regs in a mask, but just to have in case you NEED to give up your deco reg, for some reason or another. I picture the arrangement being as such; just having the full face bungeed to your deco bottle with it's own reg and everything all set to go. When it's time to deco, just switch masks and clear. But, once again, I haven't done the math on this yet. You're probably right, starting deco at 50' or 60' on 100% O2 may only make minutes of a difference in total deco time, and would then, of course, not be worth the added risk and complexity. I'm just looking for some opinions.

At one point in time (early tech) full face masks like the Aga with a gas block and full comms. were the bee's knees. Having a convulsion, or a nasty episode underwater could be lessened with a FFM. Gas switch blocks could be mounted at various locations and switches could be made as needed. However, as the sport evolved FFM's lost favor for several reasons...one of which was being able to share gas easily. Another is that they are gas hogs. I have an Exo and it's a gas hog, but darn great for working in freezing or yuck filled water.

Using a Swagelock connector a diver could effectively bring any gas into a block manifold and have a long enough hose to share with a buddy in need. I am visualising it right now and it looks really ugly.

I do hear what you are saying though. X

 

[Doc Harry]

...If they feel signs of an oxtox hit coming on, they remove the mask, if they get no signs and convulse, the mask falls away by itself and the attendant is there...

Sign me up! How much do these guys get paid?

 

[Jason Ooi]

You can have your own unit if you interesting go for full face mask, I used before interesting able to talk underwater HA-HA....

Jason:
if you're asking if I've had Technical Training, yes. I've completed TDI Advanced Nitrox, Deco Procedures, and Intro to Cave. However, I've only recently finished Deco Procedures and have yet to make it part of my regular diving. Also, I'm having a little trouble using the Scubaboard profile edit, I have more than 16-50 logged dive. ha!

 

[cg13]

I have 18 years experience with a couple of different full face masks one being the aga full face mask by interspiro. I myself am thinking of extending my range in terms of raking up some deco diving and am thinking of different solutions because I just love diving full face mask however I agree with wat is being said here some advice would and thoughts would be good at the moment I have a switch block but it is more of a bailout block not a switch it is basically a manifold which I have my main cylinder plugged into with a one way valve it then has my pony bottle plugged into it so I can afectavly breath down boath cylinders at the same rate when it is open at the block. If I where to do deco diving it would only be with one gas mix same in boath cylinders so I do not come into potential issues. However I could get a switch block but say I was to have it in the wrong position before a dive this could be fatal I can not assume this would never happen because my checks are good simply isent good enough what do people think