gas mask - full face mask

[darkmoon3d]

I was just wondering if it was possible that a gas mask could be converted to have regulator plug into front and be used as a full face mask? Crazy idea but I was just wondering if any is or had been crazy enough to do this?

 

[DA Aquamaster]

I used to collect gas masks and there are a few designs that would theoretically be possible candidates.

In fact one commercially available full face mask looks an awful lot like a military aviator oxygen mask I have seen that is designed for use in contaminated environments.

Some of the designs with a filter cannister mounted on the chin of the mask could probably be adapted to use a regulator in place of the canister.

The next concern becomes how the exhaled air is exhausted from the mask. Depending on the design, you may want to glue those valves shut or they may be desirable for purging water from the mask.

The third concern is vision as some of the less expensive masks that are otherwise suitable, provide a very poor field of vision.

A fourth concern is how easy it is to purge water from the mask as that is not normally a design criteria for gas masks.

The final concern is bouyancy. If the mask has a large face plate and good field of view, excessive bouyancy may be an issue.

From a practical standpoint, it does not make much sense to go that route. An inexpensive gas mask at best will not give you the same performance, safety or vision as an inexpensive ($50-$75) full face mask like the classic Cressi Sub FFM design.

An expensive gas mask that offers good visibility also tends to create more conversion problems and when you are done with the expense of modifying one, it is going to cost as much as or more than a medium priced FFM like the Mantis, which also offers a lot more options in terms of com equipment, surface air valves, and alternate air source ports.

So converting a gas mask is one of those things that is theoretically possible but not practical or economically attractive given the availability of commercially available FFM's that do the job better and for the same or even less money.

 

[mntdiver]

Ocean Reef did it, albeit with limited sucess. They call it the Neptune II and later versions.

 

[amascuba]

The one thing that I didn't see was.. How do you plan on equalizing your ears?

With the ScubaPro full face mask you can actually squeeze your nose so that you can equalize.

The Neptune mask has nose plugs that you press against your nasal passages when you want to clear your ears.

I'm not sure how the other masks work. Those are the two that I've used. It's just something you should think about.

 

[johnnydeep]

The other problem with these is CO2 build up!
Even with the Scuba Pro you HAVE to have a regulator mouthpiece to keep your exhaled air going out through the regulator, If you don't as you breath you will exhale CO2, the next breath you will inhale fresh air from your reg, but will also mix in some of the stagnant air from inside the mask. When you exhale again you will add just a bit more CO2 to the mix, etc. etc. etc.
The result is entirely predictible as is the result of the harder you are working on the dive with these masks the faster and more severe the problem becomes.
Its been about 15 years since I've seen an accident with one of these but the visual image of the guys face came right back to me when I read this question!
Do not use any type of mask that does not in some way keep the volume of breathable air to an absolute minimum,(i.e. a gas mask) unless, of course you are on positive ventilation!!! If you look at a gas mask they usually have very large exhaust valves and their placement is not usually conducive to being able to see if you were to exhale underwater.
Not trying to bad mouth any manufacturer or anything and I like the scubapro full face for cold water, just make sure to put a mouth piece on the reg stub inside the mask. One advantage is also that you can spit out the mouth piece and yell at your dive buddy, and be understood, not as good as coms but mutch cheaper!!

 

[Gary D.]

The one thing that I didn't see was.. How do you plan on equalizing your ears?

With the ScubaPro full face mask you can actually squeeze your nose so that you can equalize.

The Neptune mask has nose plugs that you press against your nasal passages when you want to clear your ears.

I'm not sure how the other masks work. Those are the two that I've used. It's just something you should think about.

Just like a MK-5, you learn how and sometimes real fast.

Gary D.

 

[mntdiver]

The other problem with these is CO2 build up!
Even with the Scuba Pro you HAVE to have a regulator mouthpiece to keep your exhaled air going out through the regulator, If you don't as you breath you will exhale CO2, the next breath you will inhale fresh air from your reg, but will also mix in some of the stagnant air from inside the mask. When you exhale again you will add just a bit more CO2 to the mix, etc. etc. etc.
The result is entirely predictible as is the result of the harder you are working on the dive with these masks the faster and more severe the problem becomes.
Its been about 15 years since I've seen an accident with one of these but the visual image of the guys face came right back to me when I read this question!
Do not use any type of mask that does not in some way keep the volume of breathable air to an absolute minimum,(i.e. a gas mask) unless, of course you are on positive ventilation!!! If you look at a gas mask they usually have very large exhaust valves and their placement is not usually conducive to being able to see if you were to exhale underwater.
Not trying to bad mouth any manufacturer or anything and I like the scubapro full face for cold water, just make sure to put a mouth piece on the reg stub inside the mask. One advantage is also that you can spit out the mouth piece and yell at your dive buddy, and be understood, not as good as coms but mutch cheaper!!

I'd be interested in hearing more about this accident. The CO2 accumulation in the ScubaPro mask is fairly minimal, although there can be some, it's not as if it concentrates to dangerous levels. At best you might notice a slight case of hypercapnia, if at all. The dead airspace in this mask is fairly small and is easily washed out with each breath. Unless they had it on an older version, there is no mouthpiece on the inside of the ScubaPro mask. With the Cressi you do and the M-48. The Mantis doesn't and I've had several long dives (70 minutes+) on this with no indications of hypercapnia. The average snorkel hold more dead airspace than these masks.

Positive ventilation? Are you referring to free flow or positive pressure, as with the Divator MKII positive pressure mask? The Divator along with the Poseidon have a directional flow of gas through the mask that virtually eliminates any CO2 accumulation in these full face masks.

Your post seems to perpetuate the myth that full face masks are dangerous. As I've mentioned in other posts, they've saved many more lives than injuries caused. It gets down to training. If you don't know what you're doing, you shouldn't be in the water.

Amascuba, equalization in other masks is done with a push pad, this is a rubber V shaped block mounted on a wire form. Picture this, point your index fingers up in front of you, now, bend them and put the flats of your nails together. Note the V made by the middle finger bones, place this V under your nostrils and you'll see how you equalize with the equalizing assembly of these masks.

Darkmoon3d, get a mask designed for diving, what the heck, it's only life support...

 

[darkmoon3d]

Thanks for replies. Kinda guessed that gas mask was not right thing to do. Better to ask a dumb question rather than do the dumb question.

 

[johnnydeep]

Absolutley, One thing I have learned over the years is that there are a myriad of ways that not knowing what you are doing will hurt or kill you!!
The only stupid question is the one that doesn't get asked!!!
Johnny

 

[DA Aquamaster]

The other problem with these is CO2 build up!
Even with the Scuba Pro you HAVE to have a regulator mouthpiece to keep your exhaled air going out through the regulator, If you don't as you breath you will exhale CO2, the next breath you will inhale fresh air from your reg, but will also mix in some of the stagnant air from inside the mask. When you exhale again you will add just a bit more CO2 to the mix, etc. etc. etc.
The result is entirely predictible as is the result of the harder you are working on the dive with these masks the faster and more severe the problem becomes.
Its been about 15 years since I've seen an accident with one of these but the visual image of the guys face came right back to me when I read this question!
Do not use any type of mask that does not in some way keep the volume of breathable air to an absolute minimum,(i.e. a gas mask) unless, of course you are on positive ventilation!!! If you look at a gas mask they usually have very large exhaust valves and their placement is not usually conducive to being able to see if you were to exhale underwater.
Not trying to bad mouth any manufacturer or anything and I like the scubapro full face for cold water, just make sure to put a mouth piece on the reg stub inside the mask. One advantage is also that you can spit out the mouth piece and yell at your dive buddy, and be understood, not as good as coms but mutch cheaper!!

I agree with you that it's a good idea to keep the "dead air" volume to a minimum, but a separate oral/nasal cavity is sufficient. As long as the volume is still small enough to be exhanged with each breath, CO2 is not going to build up.

Technically speaking, your mouth and throat are "dead air" spaces as well, and with a small oral nasal mask cavity, the percentage of increase of dead space is reasonably small. In any diving situation, FFM or not, you always want to avoid shallow breathing which will lead to CO2 buildup.

I used a Cressi mask for years, starting back when they were about all that was available for recreational diving, and with a lack of a separate oral nasal cavity, you did want to put the mouthpiece back in your mouth during heavy exertion to avoid issues with CO2 buildup.

My Kirby Morgan M48 also has the ability to use the mouthpiece inside the mask but it is for use when switching pods or clearing the pod as the oral/nasal volume is adequately small. Similarly the Scubapro/Mantis masks also have a separate oral nasal cavity and CO2 buildup is not an issue.