Oxygen concentrators instead of O2 tanks?

[AdamFrisch]

I've broached this subject before somewhere and I think so has also peterh337. But it's a very interesting subject, so I think it deserves its own thread. Basically, Oxygen Concentrators for the medical field work by pushing air through a sort of sieve that removes nitrogen, thereby increasing the O2. A variant of this also exists in some of the newer high end fighters, like the F22 Raptor etc. It's a very interesting and proven technology that would eliminate the hassle and rigmarole of having to fill up and keep track of O2 bottles for non-pressurised high altitude flying.

Now, these OC units used to be big and mainly designed for home use, but over the recent years they've released more and more portable models, also called POC's. Not only that, many of them are even FAA certified for altitudes up to 10.000ft for cabin use. So, what good is that, you ask? Well, independent tests show that all of the tested units could deliver satisfactory (as in sea level) O2 up to 18.000ft. This is with a Ox saturation around 92-95%. If one were to have a slightly higher resistance to depravation, perhaps even higher altitudes could be safely flown. And since they're portable, no real certification is actually needed to use them legally.

Here's some army research results:

Evaluation of an Oxygen Concentrator for Use at High Altitude

Here's one from the Respiratory Care Journal:

PERFORMANCE OF OXYGEN CONCENTRATORS AT ALTITUDE

Here's a link to the FAA's site of the certified POC models:
FAA Approved Portable Oxygen Concentrators - Positive Testing Results

These newer portable units are all battery powered, but can also be run off 12V, 24V. They're easily able to fit in almost any airplane, no matter how small. They are by no means cheap at around $3-4K, but they would perhaps eliminate needs to go to specific and more expensive airports to fill up, so could make sense over a few years of use. The most interesting units are probably the Inogen G2 and the Respironics SimplyGo. The SimplyGo is one of the few that can deliver continuous O2 flow and not only in pulse mode. I don't know what difference this makes for aviation, but I'm assuming flow is better than pulse. It can deliver up to 2Liters/min at altitude.

As soon as I get my aircraft back from annual I'll see if I can rent one and evaluate it at altitude with an oxymeter. It would save a lot of hassle, plus increase safety. And make you more relaxed and alert on longer trips. No more headaches. Also use it at night at lower altitudes without feeling you're "stealing" O2 for more important days. Doesn't eliminate the need for some O2, though, as you'd need that as an emergency backup. Also, if you're flying a lot of passengers, it might be easier (and certainly cheaper) to have them sip from the tube instead, as I doubt this POC could supply them all.


Respironics SimplyGo portable oxygen concentrator.

[peterh337]

There is no doubt that oxygen is absolutely brilliant. I use it anytime at 8000ft plus enroute because after some hours at those levels one gets tired whereas with o2 one can do a 6hr flight at FL190 and land fully awake.

People who file IFR for FL100 or whatever, to avoid having to use oxygen, are just screwing themselves because a lot of the time they end up in IMC.

I would not go for a concentrator because the cost is just very high relative to the cost of fillups. I spend about £100/year on oxygen.

Equipment certification is irrelevant for portable equipment, and if you are going to install anything "permanently" then it's the usual can of worms (337, etc).

[Hodja]

I could see how the portability would be a boon for flying clubs where the members could easily share the unit. Although it'd probably only supply 1-2 people max, so best suited for solo flying.

The cost of USD3-4k may be sorta ok for "new" users, if you haven't yet bought all the paraphernalia for the traditional solution. (oxygen cylinder, regulators etc)

I'd think it'd be crucial to hook this into the onboard power supply. Changing batteries every 2-3 hrs enroute sounds like a no-go. Looks like it'd draw ~120 watt, ie. ~5 amps on a 24 volt bus.

If stability and reliability of the unit is fine otherwise, I'd definitely be interested...

[AdamFrisch]

Yes, I agree, it has to be hooked to power, or else it becomes too much of a hassle to swap batteries. And Peter, sure it's more expensive, but wouldt the convenience be worth a little extr money? This means you could now cruise higher on your cross countries, for longer, without ever having to worry if you can refill it or if it will last all the way back?

[achimha]

That Philips product is probably designed for 250kg people eating their gallon package of ice cream while watching TV at MSL?

There is a commercial product called Oxyfly. It looks good but it's pricy, large, draws a lot of power and vibrates heavily.


I have a 48 cu.ft. builtin bottle and just filled it up today with my 200l cylinder. When used with the Mountain High O2D2 demand regulator, it lasts very long, so long that it really is of no concern. Getting the filling hoses and the cylinder cost a few hundred bucks but now I only pay around €30 for refilling the 200l cylinder which I expect to last a few years.

So I don't really see the business case for an oxygen generator.

[peterh337]

I've just done a ~25hr trip and we (2) got through about 1/2 of the "48 cu. ft" MH composite cylinder I now use.

This is using the O2D2 demand regs.

Some of it was at FL160, the rest at FL130 or so.

With that sort of kit, refills cease to be an issue, provided of course you can get them back home.

For many people, 3-4k will be good value if the refills are a hassle, which they are for many people. I had so much hassle that I now rent the big cylinder from BOC for about £100/year, but I also notice that the local scuba shop does refills (again). They used to do them but stopped because I wasn't using it for scuba

That Philips product is probably designed for 250kg people eating their gallon package of ice cream while watching TV at MSL?

Of course - that's the market.

Being able to generate o2 at up to FL200 is a different matter.

[AdamFrisch]

The cool thing about the Oxyfly unit is that even their portable model supplies up to 6 people.

Peter - I seem to recall that you sometimes struggle your way up to FL200. How much would the burn rate go up there? And out of pure interest - what climb rates do you see around FL180 to 200?

[peterh337]

The oxygen side is now fine at FL200 - getting ~95%.

The climb rate is officially close to zero at FL200 It depends on conditions. At ISA+10 (the case for much of this summer) the practical ceiling is ~FL180. At ISA, it goes to FL200 quite well.

Burn rate?

[AdamFrisch]

Oxygen, I meant. Not fuel.

[peterh337]

Well, I've just done a ~25hr trip and we (2) got through about 1/2 of the "48 cu. ft" MH composite cylinder I now use.

[Ultranomad]

Knowing how these machines operate, one can assume with a fair degree of confidence that a $3k price is what the market will bear rather than a reflection of their real cost. Indeed, here you find a similar machine, although uncertified and made in the Celestial Empire, for £171, claimed to produce oxygen in concentrations up to 90%. I am not advocating indiscriminate use of such devices for flying, but at this price it's already becoming a matter of mere curiosity to get one and test it - you may just get decent results.

[peterh337]

That's amazing. Love the chinese translation too

An the suggested applications... one can really imagine a million Chinese students hooked up to these so they can study better.

The big Q is how well it works from thin air.

[achimha]

I wouldn't be surprised if that Chinese product was a fake. How do you measure the oxygen concentration?

[Ultranomad]

I wouldn't be surprised if that Chinese product was a fake.

It may, or it may not. Only a test will show.

How do you measure the oxygen concentration?

With an oxygen sensor.

[peterh337]

The problem is that you may have to rig that sensor up in a specific way, to get a meaningful result.

[vfenext]

Worth noting that some airlines treat POC's as dangerous goods and not all types are approved for use on board commercial airliners.

[peterh337]

I would suggest that anybody having to use one on an airliner is going to have an interesting time getting their next aviation medical

[mm_flynn]

Originally Posted by Ultranomad

It may, or it may not. Only a test will show.

With an oxygen sensor.

While that will show it is concentrating oxygen, it will not show if it is adding anything else in to the output stream (like oil, parts of the PSA molecular sieve or other bits you might not be so keen to breath). The Chinese to have some form for producing knock offs that are actually dangerous. Let us know how you get on

[Pace]

I know in scuba diving various mixes are used. Nitrox is one such mix where the normal 21% oxygen Nitrogen percentage is increased to maybe 32-34% or even 36% but those are pure contained mixes!
Obviously diving is going the other way with every 33 feet equating to an atmosphere ie 14.7 psi.
Nitrogen under compression is the enemy of the diver but so is oxygen under compression. Increase the oxygen and you decrease the depth where oxygen toxicity takes place.
Increasing the oxygen % decreases the nitrogen % and hence divers can stay longer at depth but the depth is limiting due to Oxygen toxicity!
Re Breathers work by removing carbon dioxide so they are themselves filters to remove Carbon dioxide.
On a constant flow at altitude removing Nitrogen will have the effect of increasing the percentage of oxygen to compensate for the removed nitrogen but not to the factor of 100% as would be the case in breathing pure oxygen.
Therefore as I see it these OCUs will increase altitude from where suplementary oxygen is required but that altitude will be limited?
As far as I remember a few years back another route was taken to increase the altitude in unpressurised aircraft where oxygen was required and that was a simple mod reducing the rate that air escaped the airframe by attention and modification of door seals and other air escape points in an unpressurised airframe.

The other option to consider is to practice pressure breathing which will also help with altitude tolerance . See link below for tips on pressure breathing
Ten Non-medicated Ways to Cope with Altitude
My hairdresser has just come back from a climbing and walking holiday and they were covering 6 kilometres a day up at 6000 meters all she said she complained of was legs feeling like lead and headaches on one day but that is exercising.

Pace

[peterh337]

I am sticking with my best quality welding oxygen