For those out there that are also divers, I've reached the point where I need to have an O2 emergency kit handy for diving. I can't see having two separate systems for flying and diving, so I'm looking for a good recommendation on an 8-25L flow regulator that would work for both purposes. The DAN kits are nice, but have a premium $$ so I figured I can put a kit together for a little less.
Jim
For aviation:
The flows for aviation use are more like 0.5, 1 and 2 lpm continuous flow.. make sure that the regulator goes that low. If the regulator body has a 50 PSI out you can put a low flow regulator on there if the integral flowmeter doesn't select that low or in fine enough increments. A slightly more gas-conserving solution is to get a pulsed delivery regulator that senses your breathing and gives a burst on inspiration. You get the supplementation without waste. On average you breath in/out at a 1:2 ratio: there are other confounding variables, but you will waste SOME of the continuous flow.
For emergencies:
Keep in mind a typical D cylinder with 340 liters capacity at 15 LPM flow will last a very short time.. 22 minutes. Flowing at 6 lpm it will give you an hour.
So keeping your hypothetical emergency in mind on the dive boat, and guestimating how long til help gets there or you get to shore based help, and how long the tank would last.. do you want to get wrapped up into high flow, knowing it will exhaust the tank before you finish, or select a moderate flow that will still help, but allow supplementation for the entire event. Keep in mind your dive buddy is going to spend 5-6 hours in a chamber if you have a suspected DCS event. You wont fix them with 15 minutes of high flow. Normal human breathes 4-6 liters per minute tidal volume at rest.
Of course, this being my first post, I dont want to accuse a perfect stranger of being normal
My rig, when I was helping build a velocity, was going to be a fiberglass wrapped 4500 psi SCBA firefighters bottle (enough volume to support one man with all air volume for 1 hour), and put an oxygen regulator on it. It was super light, and would last hours and hours at aviation flows, so it would never have to be filled "away". I would have filled it to 2200 PSI (huge safety margin on the life limit) and at that pressure it would hold just under 1300 liters of oxy with a tank weight of 13 lbs. At 1 lpm thats... a long time.. Space considerations are a bit different in a Velocity than most RV's so... YMMV.
Now.. the disclaimer... the roll your own I envisioned is not a simple plug and play. There are issues with fittings, cylinder life limits, avoidance of hydrocarbon contamination and whatnot... Most vendors will look sideways at something like that and rightfully so, which is why I would have transfilled it myself with leased tanks from a gas supplier.