Deep diving with a FFM

[RickNC]

I thought that the work of breathing -- compared with some other masks -- was terrible with the Guardian, especially in any current; and that is apparently, a common complaint.

Any comments about the second stage?

I think after a dive I get used to it but yes definitely more difficult to breathe. I need to try and get the second stage tuned. I hear it can be done but haven't looked too much into it yet.

 

[rjack321]

So been reading a bunch about deep diving 130+ and I noticed a trend or lack of using a full face mask. Why is this? Would a FFM not be safer option due to risk of blacking out and such?

1) Why do you think loss of consciousness is a risk? What is the cause? O2 toxicity? Co2?
2) So you lose consciousness in the FFM now what's supposed to happen that the FFM solves?

 

[Bigbella]

1) Why do you think loss of consciousness is a risk? What is the cause? O2 toxicity? Co2?
2) So you lose consciousness in the FFM now what's supposed to happen that the FFM solves?

I cannot really think of a clear reason for a loss of consciousness, having used FFMs at their maximum rated depths, for years, save for some unforeseen medical issue; or perhaps some ill-advised gas mixture, though most of us were typically diving on air back then. Positive-pressure masks are more efficient at venting any potential CO2 accumulation.

“So you lose consciousness in the FFM now what's supposed to happen that the FFM solves?”

Less of a chance of drowning under certain circumstances?

In an earlier thread, I had mentioned that we came upon a fellow diver who had suffered what later turned out to be a mild epileptic seizure; and had he not been using a FFM, would likely have drowned with the use of a conventional regulator -- more than likely losing his mouthpiece.

He was still regularly breathing, when he hit the surface, and that FFM probably saved his bacon . . .

 

[Akimbo]

1) Why do you think loss of consciousness is a risk? What is the cause? O2 toxicity? Co2?

All of the above plus anoxia and a number of medical problems. The risk varies depending on your depth and dive profile. For example, a rebreather diver could experience an undetected failure or an open circuit technical diver could switch to the wrong gas that was too rich or lean in oxygen.

CO2 buildup is nominally higher on any FFM due to the larger dead air space compared to a regulator alone, but is easily managed at recreational depths. Increased gas density is the main contributor to CO2 buildup at greater depth. Many experienced divers are not even aware that they are breathing more deeply to overcome the problem.

Gas consumption doesn't have to increase, but you do have to breathe more deeply for adequate ventilation in your lungs and whatever dead air space exists. Of course the WOB (Work of Breathing) increases with depth and gas density, compounding the problem.

 

[rjack321]

I cannot really think of a clear reason for a loss of consciousness, having used FFMs at their maximum rated depths, for years, save for some unforeseen medical issue; or perhaps some ill-advised gas mixture, though most of us were typically diving on air back then. Positive-pressure masks are more efficient at venting any potential CO2 accumulation.

“So you lose consciousness in the FFM now what's supposed to happen that the FFM solves?”

Less of a chance of drowning under certain circumstances?

In an earlier thread, I had mentioned that we came upon a fellow diver who had suffered what later turned out to be a mild epileptic seizure; and had he not been using a FFM, would likely have drowned with the use of a conventional regulator -- more than likely losing his mouthpiece.

He was still regularly breathing, when he hit the surface, and that FFM probably saved his bacon . .

Yes you arent going to immediately drown now that you've had a LOC... But if you have any substantive deco your buddy is not going to be able to manage completing that - assuming they dont also lose concisousness from too dense a gas or the wrong gas etc.

 

[Bigbella]

Yes you arent going to immediately drown now that you've had a LOC... But if you have any substantive deco your buddy is not going to be able to manage completing that - assuming they dont also lose concisousness from too dense a gas or the wrong gas etc.

Anyone can come up with a dire scenario, even the crossing a busy street; but in all the time that I have used FFMs, it was the only serious accident I had ever witnessed, and the only loss of consciousness.

In that instance, we were at about 30 meters on air; and to be sure, we were close to the NDL, but thought it far more important, at the time, to check his gas gauge, and jettisoned some of his soft weights -- figuring his risk of asphyxia was a far greater certainty than that of DCS or even an embolism.

He would certainly have been dead when we came upon him, with the use of a conventional regulator.

As it was, he was eventually treated with O2 on the boat and successfully medevaced.

Thankfully, no DCS or anything else occurred with him or us; though later, he claimed that he could have died from the embarrassment . . .

 

[SlugLife]

He would certainly have been dead when we came upon him, with the use of a conventional regulator.

This is one of the reasons I use an adjustable regulator-necklace on my primary. It's fairly easy to make, just a length of bungie, knots on each end, and a zip-tie. I prefer to use a 2nd-zip tie, and not the zip-tie holding the mouth-piece. To adjust, you simply pull length of cord through the zip-tie until snug.

Basically this, minus the magnets. (I ended up ditching the breakaway-magnets. They worked, but I just eventually found them not-useful and slightly annoying)

 

[Bigbella]

Barring the use of a full-face mask or something akin to the Dräger or other brand of "safety mouthpiece," (seen below) which essentially seals the mouthpiece against your face -- used with rebreathers (and extensively tested by the French Navy, who had experienced a number of unconscious CCR divers, almost all of whom survived the ordeal), I respectfully doubt that the necklace solution would be effective at all, if one were unconscious -- since water would easily breach the seal that your lips had once provided while conscious . . .