Pelican’s Perch #13:Getting High on Welder’s Oxygen

Can't breathe welder'soxygen? Aw, horsefeathers, as my dad used to say! Show me the rule!

Oxygen is oxygen. It is the substance that matters, not the intended purpose. Thesedays, welding, medical, and aviation oxygen are exactly the same. All three come from thesame tank of liquid oxygen (LOX). The liquified form is the cleanest, purest, driest formof oxygen (or any substance) you'll find anywhere.

Oxygen, Oxygen, Who's Got the Oxygen?

For many general aviation pilots, oxygen is so difficult to find, so much trouble tobuy, and so expensive that many pilots wind up flying at lower altitudes without oxygen,when higher (with it) would be safer, and more comfortable. I know. I used to be one ofthem. Before I set up my own filling system, I frequently flew multiple long legs withoutbeing able to get a refill, and usually had to make special stops for it. Either oxygenwas not available at all, or there was no one available to do oxygen fills on weekends orafter hours. Of course, any suggestion that I might do it myself was instantly met withlooks of horror, tales of insurance requirements, and citation of "rules."

Without oxygen being readily at hand, many pilots will also "push" their ownpersonal altitude limits, often not having the faintest idea what those limits really are.It's awfully easy to take the macho approach and think "I can handle it"- andgo on up to 10,000 feet, 12,000 feet or higher without it. (Some need it above 5,000 orso!)

Unless you have been through a good altitude chamber course, or you carry one of thewonderful little Nonin Onyx pulse oximeters thatmonitor the actual oxygen saturation of your blood, it is very unlikely you will trulyappreciate how quickly human performance degenerates, and the extent to which pilots areunable to detect any loss of ability. This means you, not the other guy!

In my opinion, a cheap, readily-available source of this gas will make cross-countryflying much safer, and often smoother and more pleasant. In my mind, this enhancement tosafety would far outweigh the very remote risk of getting oxygen with harmful impuritiesin it . . . IF there were any more risk from using "welding" oxygen(which there isn't). In this column, I'd like to explore some of the issues involved inspending a few hundred bucks to set up a safe, cheap, and effective personal oxygenrefilling system.

Those Blessed Rules

Readers should be aware some of this advice may violate various rules of your hangarlandlord, your airport, the EPA or others. It is pretty clear to me that nothing hereviolates any FAA rules, but your FSDO may have a different interpretation (as FSDOs areinclined to do). So proceed at your own risk.

For all the OWTs (old wive's tales) surrounding oxygen, there is remarkably little inthe FAA and DOT publications, or even the old CARs and CAMs (pre-FAA). I have searchedextensively, and can only find a very few citations, most of them from very oldpublications that are well out of date today. None of those publications are"regulatory," only "advisory."

I found the following notation in Advisory Circular AC 43.13-1A (Acceptable Methods,Techniques, And Practices - Aircraft Inspection And Repair):

Good rule. It is easily satisfied by the modern methods of oxygen production.

The real nub of the issue is found in AC 65-9A (Airframe And Powerplant MechanicsGeneral Handbook) which is some 25 years old now, and this is as good a place as anyto extract a few words of wisdom:

Here's the biggie, in my opinion:

I have underlined "or equivalent" in the above citation because in the finalanalysis it is the legal loophole that clears the muddy water as if by magic. Some reallyheavy-duty experts have scoured government documents, and queried many governmentagencies, trying to find out just what the heck "equivalent" means in thiscontext. Its meaning appears to be nowhere specified, which leaves it up to the user in myopinion (and the opinions of those with whom I've consulted).

All that said, there are still a lot of "experts" out there - includingmedical doctors, gas suppliers, and others who have not researched the issue - who willparrot the old rules for three types of oxygen. When you are faced with these folks, asimple "Show me the reg, please?" will keep them busy for months while you goflying with your self-filled tank.

There is also the possibility that a "bad" FAA Inspector will choose to makea problem, and violate you for using "filthy welder's oxygen" instead ofAviators Breathing Oxygen (ABO). It's very doubtful the violation would be approved athigher levels, but it's better to just be discreet about it. Yes, it's legal, but some inthe FAA won't know that.

This subject got beaten to death in CompuServe's AVSIG aviation forum some time ago,and a senior FAA Inspector in Washington took the bone in his teeth and ran with it, tosatisfy his own personal curiosity. The following is a direct quote when he sort of tossedin the towel after a lot of research over many months:

The reality is simply that it all comes from the same tank. It's all the same. Somefolks just slap an ABO label on the tank and charge higher prices because there may be agreater liability, or simply because it's aviation-related.

Some Reasons ... and Dangers

Why is this stuff so hard to find, when it's in the very air we breathe? I think thereare a lot of factors. Where there used to be multiple FBOs at some airports, now there isjust one, and sometimes none at all. Without competition, there is little incentive toprovide "services" for pilots unless they are very profitable. The FBO needs tosell something that almost everyone will need, with as little time, trouble, risk, andmanpower expended as possible. (Can you spell "self-service fuel"?).

Commercial oxygen refilling systems are troublesome, take a fair amount of care andoperator training, do not provide much profit margin, and incur a fair amount of liabilityon several fronts. There is some danger in just having oxygen cylinders present, much moredanger to those using the system to replenish a customer's system, and all this createsliability that must be assumed or insured against. There is also the very real exposure ofgetting sued by the customer for some real or perceived fault of the fill or the gas. Isuspect the quite-reasonable attitude of many FBO owners is, "Why bother for a couplefills a month, when folks will only bitch at the price anyway?"

For those FBOs who do supply the service, the price they charge must be high enough toat least help cover the costs.

The real cost of the gas itself is just a few pennies per fill, but the real cost tothe FBO is much greater: perhaps $1,000 invested in the equipment, perhaps some additionalliability insurance premiums, and the lost time of an employee (often an A&Pmechanic). By the time a mechanic stops what he was doing, gets to the aircraft, removesthe bottle or finds the filler port (some are incredibly hard to get at!), does the fill,reinstalls the bottle (if necessary) and returns to his work, it's easy to lose an hour ofshop time. Either the customer needs to pay for that, or the FBO needs to "eat"it as a "customer service," hoping the customer spends enough money on fuel andother things to make up for the loss.

Oxygen cylinders and filling systems have the very real potential to cause injury ordeath if not handled and used properly. All the containers, from the big green cylindersto the smallest portable bottles, are quite literally very powerful bombs capable ofcreating an incredible blast, with damage for hundreds of yards. Fortunately, they don'texplode very often, but when they do, it's ugly. The movie scene where the scuba tankexploded in the mouth of "JAWS" was not overdone in respect to the violence of a2,000 PSI tank exploding! Even if it's just a hose blowing or breaking, great injury canoccur.

I once watched from a distance as the main filler hose on a "cascade" systembroke on the supply end, with the filler end connected, but the valve turned off,pressurizing only the filler line. As the broken hose expelled the 2,000 PSI oxygen in theline in a second or two, that hose was a lethal weapon, flailing around much too fast forthe eye to follow. Fortunately, the mechanic had walked away for some reason, and no onewas hurt. Had it been the filler end that broke, or had the fill valve been open, theflailing hose would have made it impossible to approach the system until the tank ran out.

How It's Made

Ok, warnings out of the way, just what is this stuff, anyway? I'm not going to get intothe dull chemistry of it, but there are some interesting tidbits. First called"dephlogisticated air" (love that word!), oxygen was first"discovered" in 1774 by Joseph Priestley, an English clergyman, who extracted itby heating mercury. Just what the heck he was trying to do heating mercury is unclear, butthe gas that boiled off sure did make fire burn a lot better, and he later discovered itwould support respiration. (Hmmm, just how did he "discover" that? Soundslike a modern doper looking for a new high!)

In 1895, Carl von Linde perfected the current method by which all oxygen is producedcommercially. Plain air is filtered, then alternately compressed (and thus heated) andcooled in several stages, until it is at about 2,000 PSI and 70 F. Water is drained ateach step as it condenses out, leaving the moisture content at near-zero.

Then the long, complex process of cooling the air begins, with several differentsystems used to bring the stuff to -275 F, and partly by dropping the pressure to about90 PSI, where everything except the oxygen and nitrogen is frozen, and filtered out. Byplaying with the temperatures, the oxygen vapor is boiled off, captured, cooled again tothe liquid state, and stored in special double-walled containers for transport.

Key point, here. That 90 PSI oxygen must then be re-compressed, and this is the pointthat led to all the hang-ups over "welding, medical, and aviator's" oxygen. Inyears gone by, there were several ways to do this. Breathing oxygen (medical andaviator's) was compressed by water-sealed compressors to reduce impurities added, and thatnasty old welder's oxygen might have been compressed by machinery using oil forlubrication. This is what led to the old "Welders," "Medical," and"ABO" differences of decades past.

But modern industrial processes demand gases that are at least as pure as breathinggases, so the old ways died out, and compression is now universally done by the samecompressor, using dry lubricants and the same standards of purity and cleanliness for alloxygen.

When the LOX truck pulls up to your local supplier, that oxygen is, by definition, thegood stuff. It is 99.6% pure, with the remaining 0.4% being mostly Argon, a harmless gas,and it is utterly clean and dry. The by-product, liquid nitrogen, is 99.96% pure, but mostof it is simply discarded as harmless waste. We humans use a lot more oxygen thannitrogen.

I have to laugh at some folks who insist that ABO is somehow "cleaner" thanother oxygen, when they live in the Los Angeles basin, or in some of the other big cities,and the pollution level is broadcast hourly. Please, give me some of that "pollutedoxygen" that is only 99.6% pure!

There are a couple other processes that can be used to get oxygen in the lab, but theyare too troublesome, and too expensive when producing large quantities, so all industrialand breathing oxygen is now produced by this method, making the old terms obsolete.

Medical Oxygen?

As a side note, have you ever noticed in the hospital, when patients need oxygen, theymust bubble it through a jar of water? This is because the absolutely dry stuff, as itcomes from the supply tanks, is harmful (or at least uncomfortable) to human tissues whenbreathed for long periods, and must be humidified first. So much for the OWT aboutmoisture in ABO (Aviator's Breathing Oxygen).

Truth be told, we pilots would probably be better off doing the same, as breathingoxygen can be dehydrating, at altitude. But classically, ABO has had a maximum limit of0.5% moisture, ostensibly to keep it from freezing at altitude. Note that many systems arekept inside the cabin, where freezing temps will not occur. Some airplanes have bottles innon-pressurized, or non-heated areas, of course, but with modern oxygen, it's simply anon-issue.

Frozen Pipes?

Some people express concern about the drop in temperature caused by the drop inpressure when the oxygen flows through the needle valves and regulators. This is also anon-issue, because the flow is so slow that there is very little cooling of the metaltaking place. If you simply open the valve and let the bottle exhaust itself into the openair, then you will see chilling, and perhaps a bit of frost on the outside of thehardware, but this is from the cold metal condensing moisture in the ambient air, notmoisture from the oxygen coming from the tank. The tank temperature will also drop withthe rapid pressure loss. However, this is not the way we use the system, unless you'retrying to cure a hangover, in which case you should refill the bottle on the ground,anyway.

Fire in the Hole!

Oxygen itself doesn't burn, but a blast of it, combined with fire, is spectacular.Daredevils might take a couple of breaths of oxygen, then blow through a lit cigarette,and produce a violent flame several feet long. (Don't try this at home, and if you do,don't inhale!) Much of the literature cautions against mixing oil and grease with oxygen,which is a very bad thing. At normal atmospheric pressure it might not hurt, but there aremany hydrocarbons that will burst into a violent fire spontaneously when exposed to oxygenunder even low pressures. Oil and grease are the worst at doing this. If in a containedspace, the sudden over-pressure may cause an explosion and an intense fire, as threeastronauts found out during a simulation in a pure oxygen environment.

So it can be very dangerous stuff, which leads us right back to the dangers, concerns,and liabilities incurred by FBOs who do provide oxygen filling service. It is also myintention here to give pause to those considering setting up their own refilling systems.You must understand fully what you are doing and be careful, otherwise you might get hurt.Of course, that's equally true of many other aspects of the flying machines we love, so weneed to understand the tradeoffs.

Rolling Your Own Oxygen

Your first step is to get at least a pair of the big, heavy tanks of oxygen. They'repainted a dark green for easy identification, and contain somewhere between 220 and 250cubic feet of the gas at 2,000 PSI. They're about four to five feet long, nine inches indiameter, and heavy (about 150 pounds when full). Two of them allow "cascading,"where you first fill your airplane tank from one, then "top it off" from theother. The tank you use first drops in pressure much faster. After many dozens of refillsof my small bottle, one of my tanks is down to about 1,000 PSI, the other one is at about1,500 PSI which is now the highest "charge" I can get. It is time for me to swapthe low-pressure tank for a new one, which will become the "topoff" tank. By theway, this will be my first tank change in over three years!

Any local industrial gas supplier can help you with getting these big tanks, and willusually have a variety of plans. (Look under "welding supplies" in the YellowPages.) You can lease the cylinders with some sort of plan to exchange, you can rent, or,as I did, you can purchase them outright. I paid about $175 each for two of them, with theagreement that I can just swap an empty tank for a full one any time I want for less than$20. That's not a typo, for you folks used to paying up to $50 for a refill of a small,portable bottle! You may do even better in price if you work your way up the food chain tothe central distributor for the area.

I strongly recommend that you not get into a conversation with the supplier about whyyou need oxygen, and that you definitely do not mention you intend any aviation use! Thatis an instant red flag, and many will balk at the liability, or not understanding thesituation, will insist "sorry, we can't do ABO." Just be very matter-of-factand, if pressed, tell 'em it's for your home welding shop and let it go at that.

When you transport those tanks, be careful! If one falls over and happens to break thevalve assembly off, the tank can turn into a rocket-powered missile and do great damage.Put the bottom of the tanks forward in your vehicle, and secure them so that even if youhave an accident, they'll be as safe as you can make them. Try not to hit anything on yourdrive from the gas supply house to your hangar. The thought of having an accident, withsmoking metal, and then having a whole tank of oxygen spraying all over the place is worsethan a horror movie.

For similar reasons, give some thought to where you store the big tanks in your garage,or hangar. I prefer to lay 'em down flat, so they can't fall over, and chock them, so theycan't roll around. Put them where nothing can fall on them.

Other Supplies

Any discussion of using oxygen and flying would be incomplete without mentioningseveral fine vendors of oxygen supplies.

These outfits are run by excellent, truly helpful people, who will spend copiousamounts of time on the phone, and who will go far beyond the call of duty to satisfy eventhe most difficult customer.

Mountain High sells the key to the personaloxygen filler system, a "Transfiller." This is the device that hooks between thebig supply tank, and your little one. There are several models available, priced from wellunder $100 to about $250. All are very well-made from the very best material; thedifference in price is solely due to the difference in features, not quality.

Don't stint on the cost of this device, or settle for less than the very best! Itreally needs to be made to the highest industrial standards, as this is the part that willmost likely hurt you if it fails. The hose must be as short as possible, to keep it fromflailing too much if it does fail. The Mountain High Transfiller hose is about 18"long, just enough to work with easily, yet short enough to be safe.

The least expensive Transfiller is simply a hose with an appropriate fitting at eachend, one with an o-ring, one with a nipple that fits metal-to-metal. You hook it upbetween one big tank and your small one, turn on the valves one at a time (slowly,please), wait for the pressure to equalize, and turn off both valves. I don't like toblast the gas in, but if you take about ten seconds for the equalization, you'll be fine.Little or no heating takes place, as the gas is already at pressure in the big tank, andyou're just equalizing it with the small tank. Whatever gas is already in the small tankgets compressed, and this may warm it very slightly to the touch. At this point, with bothvalves closed, you must be careful to loosen the end without the o-ring first, becausethere is high pressure still trapped in the line, and if you loosen the end with theo-ring first, you'll destroy the o-ring, and have to replace it. Crack the fitting, andlet the pressure vent. The hose is then hooked to the next big tank in the"cascade" and the process is repeated. It works, but it's a little clumsy.

The best Transfiller (naturally, the one I like the best, at about $250) comes witho-rings in each fitting, and a hand-wheel to tighten the end on the big tank. Since you'llhave to use an open-end wrench to get the usual fittings (and usually the regulator) offyour small tank, obviously there will be a wrench available for the job. It also has apressure gauge (very handy) so that you can tell what the pressures are in the big tanksas you work. Finally, it has a three-way valve that will 1) send oxygen through to thesmall tank, 2) trap the oxygen in the hose, or 3) vent the hose to the air. By thoughtfuluse of this valve, oxygen loss from venting the hose each time can be avoided. You reallyneed to think about what you're doing, because if you err, you'll start removing one ofthe fittings with pressure still on it, and there goes your o-ring. Not dangerous, butannoying, especially if you don't have a spare!

Mountain High also has Transfillers with special fittings to fit other types of oxygentanks, and interconnects to tie two or more big tanks together. I didn't bother withthese.

Step-by-Step

With the top-of-the-line Transfiller, the filling procedure is as follows:

Remove the regulator and fittings from your small tank. Mount the Transfiller with thehand-wheel end on the big tank, and the other end on your small tank. Place theTransfiller valve so it points along the hose to the big tank. Open the valve on yoursmall tank fully. You may hear the residual oxygen in your small tank hiss a little as itpressurizes the Transfiller hose. Next, gently and slowly crack the valve on the top ofthe big tank, listening for the hiss as oxygen begins to flow. By listening, and bywatching the pressure gauge, you can "gently" let the pressure equalize. Ireally don't think there's any harm in just opening the valve and letting the pressureequalize quickly, but old habits die hard.

Once the pressure has equalized, close the valve on the big tank, and rotate thethree-way valve on the Transfiller to dump the tiny bit of oxygen trapped between thosetwo valves (keeping the bulk of the hose under pressure). Move the "big-tankend" to the next big tank, open the Transfiller valve, then use the big tank's valveto add more oxygen as before. When done, close all valves, vent the Transfiller at the bigtank end, take the Transfiller off the big tank, vent the hose to the open air, remove theTransfiller from your small tank, and you're done.

If you think about each step before you do it, it's pretty simple. Otherwise,you may want to use a checklist. Blowing an o-ring is not dangerous, but it can be scarywhen you get a huge blast of oxygen after failing to turn off a valve! It's wasteful, too,and you may have to start all over.

I carry the Transfiller in the airplane with me, just in case I run out, and can find abig tank, perhaps even in a welder's setup. It will take some plain and fancy talking toconvince the FBO to let you do it, though, and the best way is to just ask them to lookthe other way, perhaps in return for a little "consideration."

Other Tricks and Gadgets

What about carrying your oxygen in the liquid form (LOX)? Great idea, you can carry alot of it in a very small space, but so sorry, it's just not practical, even though themilitary does it. To keep it in liquid form, the temperature must be kept below about-96 F, which implies either special equipment or servicing insulated tanks just beforeflight. There must also be special equipment to warm the stuff before humans can breatheit.

I use and like the ubiquitous "Oxymiser" (or"Oxysaver") system sold by all three outfits. These consist of a specialconserving cannula that contains small reservoirs and check valves, plus a little in-lineflowmeter with a floating ball to indicate oxygen flow and a vernier needle valve toadjust the flow to the desired rate. The conserving cannulas come in two flavors -"moustache" and "pendant" - but both have two small nozzles thatstick into the nostrils, with thin plastic supply tubes draped over the ears. Once inplace, I'm not even aware of it, and often find myself at the end of a flight sitting atthe gas pump still breathing oxygen!

The cannulas are officially approved up to 18,000 feet, and if you're going higher thanthat, a full-face mask is recommended. However, with the little pulse oximeter, it shouldbe easy to determine the individual need for oxygen, and with that, the "rules"can be adjusted safely.

There are basically threetypes of oxygen tanks for in-aircraft use. The old conventional steel tanks are cheap,very heavy, and must be hydro-tested every five years. Aluminum tanks are less than halfthe weight, a bit more expensive, must be hydro-tested every three years and most arelife-limited to 25 years. Finally, there are the new Kevlar tanks, which are verylight and very expensive ($1,400 and up), must be hydro-tested every three years anddiscarded after 12 years. The rules about recurrent hydro-testing and life limitationscome from the DOT, not the FAA, and there are rumors the DOT will be changing all theserules soon.

Mountain High also sells the very neat (and costly)EDS (Electronic pulse-demand Delivery System), which I would love to have, but have beentoo cheap to buy. This is mostly because my refills are now so cheap, and normally I go"out and back" and my portable bottle is sufficient for a high-altitude flighteach way (to FL210 in a normally-aspirated Bonanza).

Anyway, the EDS (about $600) is a small, battery-powered black box that replaces thenormal flow regulator, monitors the faint pressure fluctuations in the oxygen line fromnormal breathing, and delivers a small puff of oxygen only during inhalation. Since weusually spend about one-third the time inhaling and two-thirds exhaling, this dramaticallydecreases the wasted oxygen by up to 90%, or so they say. Of course, the EDS alsoregulates the flow for the altitude automatically, and can be set for day or nightrequirements.

A very nice feature of the EDS is an audible alarm signal that warns of "noflow" for any reason. If you're doing serious high-altitude work, this alone is worththe cost of the EDS, in my opinion. Without a warning system, it is all too easy to kink aline, run out, or get the regulator misadjusted, and any of these can be deadly if notdetected. Of course, using a pulse oximeter to monitor your blood O2 saturation is also anexcellent way to avoid such problems.

Full Bladders and Headaches

Some report having these problems, and they are related to the rest of this column. Iam indebted to my good friend George Braly (of GAMIjector fame) for coming up withthese suggestions.

For the headaches, simply take an aspirin before takeoff.

Solving the bladder problem is slightly more complex, but makes a lot of sense. We knowthat high-altitude flight and the continuous use of oxygen dehydrates the body, so we cantake advantage of this to some degree, and "regulate" our need for a bathroom.But don't overdo it, as dehydration impairs human performance, just as lack of oxygendoes.

Go light on the liquids for a couple hours before your flight, and make sure you makethat last-minute pre-departure bathroom visit. Climb to an altitude where you use oxygen,and put it on. From that point, you can either sip liquids to keep from getting toodehydrated, or drink the liquid of your choice, up to about 16 ounces every couple ofhours. More at higher altitudes, less at lower altitudes. Higher altitudes (and moreoxygen use) will permit longer flights without discomfort, even for us older folks! Youwill probably find no pressing need after landing, even on very long nonstop flights. Somealso find it useful to munch on potato chips, pretzels, or other salty snacks during theflight, as it seems to soak up fluid, rather than allowing it to go to the bladder.

Mike Busch, who does a good deal of flight-level flying in his unpressurized CessnaT310R, suggests carrying a small sack of seedless grapes, preferably de-stemmed beforeflight. The grapes provide an excellent source of moisture and sugar in a convenient form,and they won't spill if you get into turbulence!

Summary

If you use supplemental oxygen (and you should), think about setting up your ownfilling system. The $600 price tag (cylinders, Transfiller, etc.) may seem high until youfigure that 10 or 15 refills at your (mostly unwilling) FBO is the "break-even"point. After that, you can play cheap airline pilot, and chortle to yourself as you loadup on "nearly free" oxygen. Hey, it makes my day!

Once you do this, you'll find yourself just putting on that cannula from 10,000 feet onup (or sometimes lower), without regard for the trivial cost, or the fear of running outbefore you can find a refill. Just top off your bottle before or after every flight, andyou'll always have plenty of O2 available.

This, in turn, will lead you to doing more high-altitude flying, where the engines aremore efficient, the weather tends to be better and smoother, and where you have many moreoptions to avoid ice and other unpleasantness. With the better fuel (and bladder)specifics, you'll be able to go longer distances and make fewer stops, reducing the wearand tear on your airplane.

Be careful up there!