FFM in Technical Diving

[kelemvor]

I've been watching youtube videos of a lot of technical dives lately and I've decided to put off cave/technical training for another year. Maybe when I get to 200 dives or something. However, I do have a question. Why do tech/cave divers not use full facemasks with comms? I've even looked specifically for these in videos, and found none. Is there some inherent incompatibility between the two? Certainly cost cannot be an issue given all the other extreme costs involved, so I'm curious what it is.

 

[KD8NPB]

Gas switching is not possible, except with the Kirby Morgan M48.

 

[tplyons]

Most FFM's don't have the capability of gas switches... If I recall one or two do, they use pods with attached second stages.

 

[lowviz]

I have a full cave cert (although I don't currently consider myself to be a cave diver) and a real FFM cert.

In caving, there is a huge "team" aspect that I can completely appreciate. An FFM is much more "self-centric" than a simple mask and highly practiced "team" survival drills.

 

[Nwcid]

Not that I am condoning this, and I understand why tec divers do what they do.

I know many of the FFM come with a QD hose connection. Rebreathers divers with BOV also use OD hose connections.

Obviously this increases failure points. Tec gear is the way it is having been tested throughly. But could QD be used for gas switching?

 

[Akimbo]

… But could QD be used for gas switching?

Sure, but everybody would have to be on the same page in order to share gas. Then there is the question of what happens when the second stage in the mask fails? The “standard practice” is to carry a half-mask with you and switch to standard second stages.

Of course you need to maintain your non-verbal communications skills because you must assume a failure there too. It starts to get pretty complicated once you build a failure-mode matrix.

 

[Nwcid]

As I said it fully understand why they make the choices they make, including team diving. I follow most of their ideas.

 

[Phil_C]

I've got a couple of days diving on a FFM and surface supplied diving course booked in three weeks time - when I last dived with these guys in August one, a qualified commercial diver, had a FFM and had some sort of switch block mounted near his chest, this had one hose out - to his mask, and several in. I think his bail out and deco gases switched into it, along with his back gas, but I guess the risk of getting a switch wrong would be much more with a set-up like this.

Not sure whether this is a common thing or not - Phil.

 

[Akimbo]

Commercial and military surface supplied diving has most of its backup and all the decompression gas on deck and switched by the diving supervisor. Hats and masks have a valve for back-mounted bailout gas. The second valve controls free-flow into the hat, which is also the backup to a failed regulator.

Kirby Morgan is the leading manufacture of hats and masks. Lots of images on their site.

 

[Phil_C]

Yes - but this guy was diving scuba, not surface supplied, with some some of switching manifold fitted between the tanks and FFM. it was a metal block about 8 inches long and maybe 1 inch wide and deep which all the hoses came in to. I had never seen anything like it before. Phil



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