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Thread: Loop volume control with oronasal FFM

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    RBW Member Pascal74 is an unknown quantity at this point Pascal74's Avatar
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    Meg CE

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    Loop volume control with oronasal FFM

    Hi all,

    I am really not familiar with FFM's, sorry...
    Surely a stupid question but I don't get how one can exhale out of the loop during ascent to keep the loop volume even with an oronasal FFM.
    The oronasal choice would be to have the nose pads for ears equalizing (OTS guardian) without requesting fingers/hand action like for the bite piece FFM such as the Panorama.
    Thanks for your valuable inputs.

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    JJ, Flex

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    Loop volume control with oronasal FFM

    Absolutely imperative to have a BOV when using a FFM. To vent loop volume on ascent with a Guardian or AGA with oronasal cup, inhale from loop, switch BOV, exhale into water column, switch back BOV. Yes, it is a complicated multitasking skill. Which is why some folks prefer the bite piece of the Nova with a p-port reg so you can just inhale from the mouth and exhale through your nose to vent gas.


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    RBW Member Pascal74 is an unknown quantity at this point Pascal74's Avatar
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    Meg CE

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    Re: Loop volume control with oronasal FFM

    Quote Originally Posted by kwinter  View Original Post
    Absolutely imperative to have a BOV when using a FFM. To vent loop volume on ascent with a Guardian or AGA with oronasal cup, inhale from loop, switch BOV, exhale into water column, switch back BOV. Yes, it is a complicated multitasking skill. Which is why some folks prefer the bite piece of the Nova with a p-port reg so you can just inhale from the mouth and exhale through your nose to vent gas.


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    Thanks for the information.
    That's indeed not so practical.
    Do you know any FFM in which there is a bite piece and with the kind of nose pads like in the Guardian?

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    JJ, Flex

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    Loop volume control with oronasal FFM

    I don't know of any mask that fits that description. But there is something in the library from years ago about a modification to an AGA mask that put a vent into the skirt. I don't remember the details of how it worked, but I'll try to find it when I get some time on my desktop. Too hard to do on the cell.

    BTW the reason I don't like a bite piece is because it interferes with the ability to use comms. I think the inconvenience of venting through the BOV is worth the advantage of comms.


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    Last edited by kwinter; 20th May 2014 at 14:33.
    Ken

    Quote Originally Posted by Dsix36  View Original Post
    Just remember that listening to an idiot such as myself may very well get your arse dead.

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    RBW Member Kristen24060 is on a distinguished road Kristen24060 is on a distinguished road Kristen24060's Avatar
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    Re: Loop volume control with oronasal FFM

    I recently switched to a Draeger Nova. Mine has a bite-piece and no oro-nasal cup. I try to avoid exhaling into the mask as it has a tendency to fog the visor if my antifog (spittle or sea drops) has worn off.

    Still, it is possible to exhale into the mask to vent gas. It just vents at the seal at the top of the mask. Sometimes this causes a trickle of a leak, but this is no big deal. If I hold the mask to my face, it vents from the chin port with no leaks and also purging any water collecting at the bottom of the mask.

    Usually, I use a dump/vent valve on my exhale counterlung to vent the expanding gas.

    By the way, use of coms would be impossible for me in this mask as the bite piece is too long to push out of the way enough to talk. For folks with larger heads, YMMV.

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    Re: Loop volume control with oronasal FFM

    Quote Originally Posted by Kristen24060  View Original Post
    Usually, I use a dump/vent valve on my exhale counterlung to vent the expanding gas.
    Yes, I should have mentioned this is the way I did it with front CLs. But now with BMCL that is not an option. I couldn't tell from the OP what kind of lungs he had. Now I see it is Meg or Inspo, so I don't see why he couldn't vent from the OPV.

    BTW, here is the link to the article in the library.
    http://www.rebreatherworld.com/showthread.php?t=2274

    You will see that the author removed his oronasal cup and inserted a mouthpiece because of the concern for CO2 buildup. I have never had a problem, but then I avoid hard work on CCR. I think he did it for a living.

    The last photo in the article shows the dump valve he added in the skirt. It may be similar to what Kristen referred to as a "chin port" in the Nova.
    Last edited by kwinter; 20th May 2014 at 16:26.
    Ken

    Quote Originally Posted by Dsix36  View Original Post
    Just remember that listening to an idiot such as myself may very well get your arse dead.

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    RBW Member Pascal74 is an unknown quantity at this point Pascal74's Avatar
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    Meg CE

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    Re: Loop volume control with oronasal FFM

    Thanks for the link, kwinter.

    The reason why I asked for venting without using the OPV is because the usage would be for my son who has a very limited hands mobility.
    He is tetraplegic following an accident 9 month back and he dived my good old inspo classic (with BOV) before the accident.
    We are just going back to the lake after few months of pool training in OC.
    We just did the first trial of donning and dofing the rebreather last week-end, staying after on surface and breathing from the rebreather .
    All OK, he can even manage a dil flush. Anyway, still a long way to go...
    For him it is much easier to vent by exhaling through the nose or around the bite piece.
    Of course many things will have to be done for him by the small dive team around him while diving OC or CCR, but anything he will be able to achieve by himself is better.
    The reason why a FFM is considered is because of sensitivity to cold water and possibility to equalize without hands (OTS guardian would have been considered but switching the BOV from CC to OC each time venting is requested wouldn't be possible, opening the OPV should be possible but too complicated to achieve as a repeated movement).
    The panorama nova R would be the choice as far as venting is concerned because it is including a bite piece thus giving a possibility to vent through the nose, but the equalizing requests hands for what I see.
    Any people did a modification giving a possibility to equalize without hands?

    Thanks for your ideas and advises.

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    JJ, Flex

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    Loop volume control with oronasal FFM

    Sorry I haven't followed up on this. Now I appreciate what you are trying to do. But I have additional concerns. Equalizing with the AGA or Guardian also requires at least one hand. You must push up on the bottom of the mask to block the nose with the rubber piece in both of those masks. I have a friend who didn't even use the nose block and could clear just by swallowing. But I can't duplicate that. If the Nova's "windshield wiper" nose block is a one-handed operation, that might even be easier. It depends on what functionality your son has. One is a pushing up action while the other is a pinching action.

    Best of luck.


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    Ken

    Quote Originally Posted by Dsix36  View Original Post
    Just remember that listening to an idiot such as myself may very well get your arse dead.

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    RBW Member turtle dude is an unknown quantity at this point turtle dude's Avatar
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    Inspo classic hacked about

    Re: Loop volume control with oronasal FFM

    Hi,
    I saw in one of the Co2 posts that they removed the oral/naisel cup and replaced with the bite piece then used the old style navy nose clip?? might be a solution?? could still vent from around mouth, and if the mask spider/straps wasn't excessivly tight should still vent around skirt.

    Regards

    Baz.

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    JJ, Flex

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    Loop volume control with oronasal FFM

    I don't think that would work, Baz. If the spider was loose enough to vent, it would allow water in. And you would have to completely plug the mouthpiece with your tongue to force the gas out the skirt. Theoretically possible, but highly unlikely IMHO.


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    Ken

    Quote Originally Posted by Dsix36  View Original Post
    Just remember that listening to an idiot such as myself may very well get your arse dead.

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