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 (http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA371747)

Here's one from the Respiratory Care Journal:

PERFORMANCE OF OXYGEN CONCENTRATORS AT ALTITUDE (http://www.rcjournal.com/abstracts/2009/?id=678059)

Here's a link to the FAA's site of the certified POC models:
FAA Approved Portable Oxygen Concentrators - Positive Testing Results (http://www.faa.gov/about/initiatives/cabin_safety/portable_oxygen/)

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.

http://simplygo.respironics.com/images/gallery/big00.jpg
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 (http://www.oxyfly.com/). It looks good but it's pricy, large, draws a lot of power and vibrates heavily.
http://www.oxyfly.com/tl_files/duerrtechnik/images/oxyfly/oxyfly_festinstallation.jpg

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 (http://www.ebay.co.uk/itm/PORTABLE-OXYGEN-GENERATOR-CONCENTRATOR-ADJUSTABLE-1L-5L-90-HOME-CAR-TRAVEL-p6-/230717344201?pt=UK_Health_Beauty_Mobility_Disability_Medical _ET&hash=item35b7d349c9) 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 (http://en.wikipedia.org/wiki/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 :E

[mm_flynn]

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

With an oxygen sensor (http://en.wikipedia.org/wiki/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 :ok:

[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 (http://www.bodyresults.com/e2altitudecoping.asp)
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 :E

http://www.peter2000.co.uk/aviation/oxygen/mh-2012.jpg

[achimha]

Peter, looks like you're turning your 4 seater into a 3 seater by installing a 4 place oxygen system? :)

Would it be difficult to install the bottle somewhere in the rear cone of the airplane? Doesn't the TB20 have a factory oxygen option which you could install as a modification?

[Pace]

Ginko Biloba and an aspirin are also a good safeguard on high altitude flights even ones at levels where you do not quite need oxygen.
Pressure breathing as described was developed in WW2 AND DOES WORK.
To the system of ridding CO2 allowing a higher concentration of 02 i would add with pressure breathing on inhalation to full lung capacity tighten stomach muscles and the diaphram effectively compressing the full lung of air for a few seconds.

Pace

[peterh337]

looks like you're turning your 4 seater into a 3 seater by installing a 4 place oxygen system?That is indeed true, unless the rear RHS passenger is willing to have the cylinder, ahem, in between her legs (http://en.wikipedia.org/wiki/Essex_girl) :E

Would it be difficult to install the bottle somewhere in the rear cone of the airplane?One could but you get the issue that you cannot see the pressure gauge anymore (**). That's why planes with fitted oxygen systems (most turbocharged models) and the cylinder in the back have a high pressure pipe (one with a really tiny inside diameter, so it doesn't have to be thick) running to a pressure gauge in the panel.

However I also carry the life raft and an emergency bag on that seat, so carrying four people would mean some reorganisation anyway. Also with 3 modern adults and some junk, you are at MTOW - as with most if not all 4 seaters.

Ginko Biloba and an aspirin are also a good safeguard on high altitude flights even ones at levels where you do not quite need oxygenI am sure it stops you getting a headache during the flight but you just end up totally sh*agged after you land, which is hardly what you want with lady passengers :E

Pressure breathing as described was developed in WW2 AND DOES WORK.It must work, as you say, but it requires conscious effort. That's why the O2D2 electronic demand reg is so good; it does away with the conscious effort (apart from having to keep your mouth shut :) ) all the way to FL200.

(**) and if you can't reach the valve you cannot turn the gas on or off. With a demand regulator, there isn't any flow (in theory) if nobody is drawing anything out of the cannulas, but there is a tiny leakage. With a mask, you can run that with the O2D2 as well but often they are constant-flow. I need to be able to reach that valve, and normally I reach over and shut it off when descending through a few thousand feet, just in case I forget later.

Now that I think of it, I think fitted o2 systems must be routing the main gas flow all the way to the panel first... otherwise where do you shut it off after each flight?

[Pace]

Peter

You probably pressure breath with the Girlfriend without realizing it :E

A cylinder that size between the RHS Females legs would be wishful thinking well by her anyway :E and very uncomfortable

Pace

[peterh337]

Not if she is into horseriding :E

[Pace]

Peter

The Seneca Five had a very neat built in system to supply six persons with attachment points set in the ceiling.
The masks would attach to those points.
Portable bottles are great for seasoned fliers but disconcerting for nervous fliers.
Flying over weather with two female business Pax in the back I was forced up to FL190 to cross weather and icing enroute to Belgium.
The one lady was perfectly happy and relaxed breathing oxygen the other freaked out and started hyperventilating (I have that effect on female PAX:E)
Once we had cleared the weather I descended down to non oxygen levels.
The freaked out PAX would not remove her mask and remained with it on till touchdown.
I do not know what she would have made of entering an aircraft full of bottles and pipework?

As stated I do vaguely remember a mod being offered on unpressurised aircraft which was door seals and other bits and pieces to limit air escaping! It was supposed to be good up to 18000 feet

Pace

[Golf-Sierra]

As stated I do vaguely remember a mod being offered on unpressurised aircraft which was door seals and other bits and pieces to limit air escaping! It was supposed to be good up to 18000 feet

It didn't coincide with the 1st of April by any chance?


Golf-Sierra

[peterh337]

I would never advocate oxygen (cannulas etc) for paying passengers, for "non responsible" kids, or for anybody who is nervous anyway.

For those, an entry level is a PA46.

If it has to be a twin (paying passengers) then you have to stick to mission profiles which can be scud run e.g. the C.I. to UK S. Coast kind of run. Or move to a 421 or higher...

But the whole "concept" of oxygen is much simpler and more comfortable than most people think.

You get comfortable and safe flying at higher altitudes, better IFR routings, more ATC co-operation...

People go to all kinds of contorted lengths to avoid using oxygen but really it's easy.

What I find sad is to read of fatal accidents which - pilot / decisionmaking related factors notwithstanding - would simply not have happened if they had used oxygen to get themselves to a decent altitude.

[achimha]

I agree, oxygen hardly means any discomfort if done right. I have a similar setup like Peter but builtin with the O2D2. Even after several hours in FL160-200, I do not feel any extra exhaustion compared to a flight below 10,000ft. The cannulas work great and you don't notice their presence after some time. I usually have passengers put them on before takeoff and tell them it's just for their comfort, there is no danger of suffocation. The O2D2 automatically kicks in when passing FL100 (configurable). Another huge benefit of the O2D2 is that you don't have that constant flow of super dry and cold air into your nose.

I only carry masks for emergency and small children.