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Oxygen Demand Valve System explained (Read 8618 times)
ClusterChuck
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Oxygen Demand Valve System explained
Nov 9th, 2008 at 1:59am
 
I was asked in another thread what the demand valve system was, and how did it work.  I decided it deserved its own thread, so that you can always come back to it.

This is one of my systems.  It shows the mask and the regulator, attached to my tank.
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The demand valve is a mask and special valve system that works quite different from the more familiar non-rebreathing mask.  With a non-rebreathing mask, the oxygen flows from your tank, through a regulator, that has a dial on it so that you can select the speed that it releases the oxygen.  It then flows through a light weight hose, to the reservoir bag of your non-rebreather mask.  It collects there, until you breath in (inhale), in the mask, and the little valve opens, and lets the pure oxygen into the mask, and then into your lungs.

When you stop breathing in, and then exhale, the valve at the top of the bag closes, allowing the bag to refill with oxygen, and another valve opens so that the exhaled air is exhausted into the room, and not back into the reservoir bag.

The whole process starts over, with your next inhale.

Throughout this process, the oxygen is running into the bag, continuously, until you shut it off at the tank or the regulator.

The Demand Valve System works a bit differently.  First of all, it needs a special regulator, with at least one DISS fitting, that does NOT go through the LPM selector.  The oxygen coming out of this orifice is not measured by how many LPM it releases, but by the PSI (Pounds per Square Inch) it is manufactured for.  Most are in the 40 to 60 PSI range.

Here is a picture of one of my regulators (with CGA870 fitting for "E" tank).  Notice that there is still a nipple to connect your non-rebreather mask, but there are also two DISS fittings, for the demand valve system.  Not all  regulators have two DISS fittings:
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Now, connected to this DISS fitting, is a high pressure hose that goes to your demand valve, and mask. Inside the demand valve is a diaphragm or valve, that stays closed, and does not release any oxygen, until a very low pressure is applied to the other side.  That very low pressure is generated by your inhaling from the mask.  With a good mask and demand valve, you do not need to suck HARD.  It will work with just a slight bit more suction than normal breathing.  As soon as you stop inhaling, the valve closes, and no more oxygen is allowed to pass through.

This is where the name comes from.  Until there is a demand for oxygen (you inhale) no oxygen is released.  As soon as you present a demand (inhale) the valve opens and stays open until you stop inhaling.

How fast is the oxygen passing into you?  I don't know.  I am guessing that it is somewhere around 40 to 50 LPM.  There are others that are much smarter than I am that can more accurately answer that question.  All I know is that I have all the oxygen that I need!  I never have to worry about a bag collapsing, and running out of oxygen for that breath.

The two best features, in my mind, are that you never run out of oxygen (as long as there is some in your tank, of course) for any breath, regardless how fast and deep you inhale.  (This works EXTREMELY well when you are hyperventilating as part of your treatment!), and the second feature is that as soon as you stop inhaling, the oxygen stops flowing.  I never shut my tank off.  When I need it, I just pick up the mask, and start inhaling!  This is especially important when you fall asleep (as I often do) once the hit is almost gone, and you are sucking the oxygen just a little more, to make sure it is fully aborted.  Your hand and mask fall away from your face (there are no straps to hold it to your face) and the flow stops!

These systems were designed and used by emergency personnel.  Because of this, there is a button on the back of the demand valve, that when pressed, opens the valve, and lets the oxygen pass.  This is under pressure, so that if you are unconscious, and not breathing, it forces air into your lungs.  We can use this button, if we want, but I rarely do.

Now these systems are CONSIDERABLY more expensive than the non-rebreathing systems.  They run in the $300.00 to $500.00 USD price range.  But, those of us that have them, swear by them!

I hope this explains what the system is, and how it works.  If you have any questions, please do not be afraid to ask them.

If you wish to purchase one, you can get one right over there to the left, at the oxygen info tab, from Linde.  One of my systems is from them, and it is GREAT!  If you can afford it, I highly recommend it.

Chuck, the oxygen pusher
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« Last Edit: Nov 10th, 2008 at 2:21am by ClusterChuck »  

CAUTION:  Do NOT smoke when using or around oxygen.  Oxygen can permeate your clothing or bedding.  Wait, before lighting cigarette or flame.  

Keep fire extinguisher available, and charged.
ClusterChuck  
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MrsT
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Re: Oxygen Demand Valve System explained
Reply #1 - Nov 9th, 2008 at 2:25am
 
Thank you so much for the thorough explanation, Chuck.  I shall start saving for the next episode...... Smiley.
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Jonny
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Re: Oxygen Demand Valve System explained
Reply #2 - Nov 9th, 2008 at 2:37am
 
ClusterChuck wrote on Nov 9th, 2008 at 1:59am:
there is a button on the back of the demand valve, that when pressed, opens the valve, and lets the oxygen pass.  This is under pressure, so that if you are unconscious, and not breathing, it forces air into your lungs.  We can use this button, if we want, but I rarely do.


Lets just say I was  unconscious, and not breathing.......Would I be pressing any buttons?.....LOL  Grin

Just asking!  Wink
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ClusterChuck
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Re: Oxygen Demand Valve System explained
Reply #3 - Nov 9th, 2008 at 2:56am
 
Quote:
Lets just say I was  unconscious, and not breathing.......


I guess, in a case like this, desperate measures are required.  I would have no other choice, but to give you mouth to mouth resuscitation ... WITH a little tongue action ...

<sigh>

The sacrifices we have to make ...

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CAUTION:  Do NOT smoke when using or around oxygen.  Oxygen can permeate your clothing or bedding.  Wait, before lighting cigarette or flame.  

Keep fire extinguisher available, and charged.
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Ray
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Re: Oxygen Demand Valve System explained
Reply #4 - Nov 9th, 2008 at 1:37pm
 
Just for kicks, here's my demand valve rig.

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Ray
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WWW raymond.schwartz759 rayplace raymond.schwartz759 raymond759  
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