View Full Version : "Pure oxygen is flammable." True or false?

01-06-2006, 04:34 AM
In the book Welding by Don Geary the author states on page 7, "Pure oxygen is flammable." I disagree.

The way I understand it, oxygen is required for oxidation but oxygen is not a fuel. The higher the concentration of available oxygen the faster an item will oxidize. For example, a lighted cigarette can flare up into a flame in the presence of a high concentration of oxygen.

If oxygen is flammable why won't the oxygen from an oxygen tank in an oxyacetylene outfit ignite?

The reason I'm asking is that I've read and heard this statement so often that I'm beginning to doubt myself.


Forrest Addy
01-06-2006, 04:53 AM
You are correct. Geary's statement is false.

Oxygen is one third of the fuel, oxy, heat source triad that initiates conmbustion. Take away one and there is no combustion. Oxygen is not a fuel. It's an oxidizer which if present in larger concentration results in more vigorous combustion. Oxidizers include halogen gasses like chlorine, sulfur, and other elenents that accept valence electrons with a consequent release of chemical energy. I think. It's been 45 years since HS chemistry.

So, oxygen is not a fuel. It's an oxidizer. What's his name either has his facts wrong or is guilty of a dumb blurt. Geary needs to bring out the hazards of working with oxygen but without committing technical solecisms.

I like what's printed on the oxy cylinder label: "Caution!! Oxygen vigorously accellerates combustion." This is true. I once saw a safety film in HS on fire hazards. In one demo a plain cotton tich hospital mattress was saturated with oxygen and ignited on a firing range. It went up like a pound of black powder poured out on the ground.

And yes, my buddies had to try it with a pissy old crib mattress and a dad's welding oxy. It worked as advertized. What the nmovie didn't mention was how hard it is to extinguish blazing mattress fragments and dispose of the evidence before the Fire Departnent arrived.

[This message has been edited by Forrest Addy (edited 01-06-2006).]

01-06-2006, 05:24 AM
I have a welding book at home but I can't remember the title of it at the moment where the author states that you can cut with an oxy acetylene cutting torch even after cutting off the acetylene. He says that you start the cut as normal and then shut off the acetylene while keeping the torch moving into the cut. He says as long as the torch keeps moving the oxygen will continue to cut the metal. I have never tried this with my torch at home.

01-06-2006, 05:38 AM
I tried this and it works. It's tricky but once the steel hits the kindling point and you hit the cutting torch lever you can shut off the acetylene and watch the steel continue to burn.

Richar Finch talks about this in Welder's Handbook.

Another book (the one with the gray cover) talks about a lance being used to apply only oxygen to an initially heated piece of steel. It talks about piercing steel several feet thick using this method. The lance is a consumable hollow metal tube that can be several feet long and only delivers oxygen.

01-06-2006, 05:54 AM
Forest Andy:

I read the first post then read yours you did a A1 job. I thought about the first post and how I would answer it. You read my mind almost 100%. It was scary we must have had the same science teacher in another life.
I commend you for being so thorough with your post.

Norman Atkinson
01-06-2006, 06:09 AM
This is chemistry which dates back to the Pholgiston theory and Joseph Priestly in 1774.

What you have read is something as old as the debunked belief. Forrest Addy is perfectly correct- but this is first year Chemistry stuff. If you ain't got to this level, you should choose to leave the damned stuff alone. Other instances of just how dangerous Oxy is all too true.

Again, with steel- iron red hot, the introduction of pure oxygen from a torch is simply creating an iron oxide from the parent metal- and a gap or cut where it fell in sparks in your ear or in your neck!
It's called reducing- although you might think otherwise from the bad language- which is a by-product.

Really, you should go back to or re-learn the basics in chemistry or physics- before venturing into second level stuff such as welding.


Evan's jet powered human post illustrates the oxygen chemistry. Hydrogen Peroxide is
water H2 O but with an atom of oxygen hanging on to make it H2 O2. In simple terms, it is the stuff to clean wounds or teeth or dirty clothes. It frees the atom off with surprising results. The rest of the gubbins quiets down to water or steam again!
Thank , you Evan, for your help in Distance Chemistry lessons.

[This message has been edited by NORMAN ATKINSON (edited 01-06-2006).]

01-06-2006, 06:39 AM
Norman: I think the jet was a 'real jet',
a miniature turbine engine fueled with kerosene and air breathing with no added oxydizers. H202 devices are usually rocket engines, not jet engines and use essentially pure H2O2 or with only a few % of water.

Norman Atkinson
01-06-2006, 07:12 AM
Wasser "real jet"?
I came from an era of Lorin and Babst and athodyds. Goblin engines, Meteors with re-heats, V1's with Shmitt Argos engines and V2's from the Verner Braun stable before he was defected. Miss Braun was piloting, pilotless V1's and we were using rockets on jet aircraft.
Then of course we were introducing water and glycol into Merlins and Griffon Spitfires which were fired up by Coffman cartridges which were strictly rockets.

And then I was almost 20!

My mistook! Got a City and Guilds in Welding.That I do remember.


01-06-2006, 08:08 AM
Oxygen will make everything burn, including you. Just ask the apollo astronauts. A unshielded switch ignited the blaze.

When you prep chemical lines for oxygen service you swab them out with a full-evaporating cleaner, the least dab of oil and you can have a blaze. It lowers the self ignition point that low. Oil the regulators on your oxy-actylene bottles and have the same results.

Oxygen is one essential part of the flaming process. Perhaps why it was included as flammable. It takes both to burn, even steel at the right temperature. It takes a oxidizer and a fuel to burn.

Norman Atkinson
01-06-2006, 08:24 AM
Exactly! I am guilty of hogging the post and it was time to give others a chance to add their contributions.
As each post appears, each bears out earlier warnings.
Cheers and thanks, Mate


[This message has been edited by NORMAN ATKINSON (edited 01-06-2006).]

01-06-2006, 08:26 AM
While in vocatioal school I was about to use the acetelene torch. A friend near by had a cigarette so I asked him for a light and he held out his smoke. I turned the acetelene on and held the torch to it. Just then another student said "that won't work" I then turned on the oxygen and POOF! Made an instant believer.
Had fuel, had heat, added oxygen, got fire.

Solecism....betcha don't get to use that word every day.

H2O2 aka T-Stoff?

01-06-2006, 08:31 AM
Now Magnesuim: Some bright young man from NORTH GEORGIA, I won't admit who..

Took a whole shovel full of magnesuim shavings and put them into a campfire at the lake. GOD, it was so bright My shadow was on the trees hundreds of yards away, Since the people on the highway about 100 yards away were having trouble and stopping, The magnesuim was shoveled up and put into the bay, muddy water.

Mucho to everyones surprise it self-oxidizes and burns underwater once ignited. You could see it under the muddy water burning brightly.

Now, imagine if I had added aluminum and iron filings to the mix? a meltdown of the shovel..

01-06-2006, 08:32 AM
To add to what's been said - no O2 is not flammable by itself, but it's presence can get almost anything to burn, and fast.

Somewhere out there, there's a video of a guy in an asbestos suit with a flask of LOX at the end of a 15' pole. He pours it on a hot BBQ grill in the middle of a bright sunny day, and the white-hot meltdown of the grill washes out the entire scene in bright white. It's pretty impressive, albeit crazy.

I've also heard that a charcoal briquette soaked in LOX has the explosive power of a stick of dynamite.

This all goes to why I'm reluctant to have an OA welding setup at my home.


Weston Bye
01-06-2006, 08:36 AM
I remember a picture of a mildly burned Navy pilot - his lips were dry so he applied Chapstick to his lips while suiting up for a flight. Ignited when he put on his oxygen mask. 1st & 2nd degree burns to lips, nose & cheeks under the mask.


01-06-2006, 08:38 AM
The hydrogen peroxide as used in the Bell jet pack doesn't burn either. It undergoes an exothermic reaction when promoted by a catalyst such as platinum. The reaction releases the binding energy of the extra oxygen atom and goes: 2xH2O2>O2+2H2O.

The end result is water in the form of superheated steam and free oxygen.

01-06-2006, 09:15 AM
Evan, platnuim is a extra in the catalyst, Seems silver is the main.

Yeah, I had a small one here. WOnder I didn't die, huh?

Screen catalysts can be purchased much cheaper than made. They erode as running, it is not free power that last forever.

Just like the dye process I used to build, take a metering device, *micro-motion, a real good valving system, a high pressure feedback and this can be improved immensely. Imagine a boiler the size of a lunchbox.

I just want to build a drag car. No lost vapor cloud, just 400mph contained steam and smoking tires. Does that sound dangerous? well watch racing, the blower explosions are pretty spectacular.

01-06-2006, 09:23 AM
Hi There,

<font face="Verdana, Arial" size="2"> I've also heard that a charcoal briquette soaked in LOX has the explosive power of a stick of dynamite. </font>

My father-in-law used to blow stumps with LOX. He said he used a cigarette soaked in LOX for small stumps and a cigar soaked in LOX for big stumps. http://bbs.homeshopmachinist.net//biggrin.gif

Good Luck!
-Blue Chips-

Norman Atkinson
01-06-2006, 09:33 AM
I still have my Battle Bowler left over from the last big " Bun Fight"

Let me know when I have to wear it again.

I have always kept my red jacket so that the blood didn't show and my brown trousers when we knew the size of the French Fleet but David and Evan- every man has a point when he has to say " Duck"

Petrified Plonker

01-06-2006, 09:40 AM
Thanks Forrest! I guess that's why I've never seen a FLAMMABLE sticker on an oxygen tank.

I knew I learned back in junior high school that oxygen doesn't burn but is necessary for combustion but like I said, I've heard it wrong so many times that I guess I almost began to believe it.


01-06-2006, 09:55 AM
Won't some hydrocarbon products spontaneously ignite in the presence of pure 02? I seem to recall that Kero and pure 02 don't need an igniter.

01-06-2006, 10:06 AM
Are you thinking of diesel engines?

01-06-2006, 10:08 AM
Yes, it lowers the flash ignition point to such a low ambient temperature level. Spontaneous combustion can occur even with "hay and straw" stored thou. Human spontaneous combustion is quite interesting to read about.

We used to keep a nitrogen blanket on the top of flammable vessels. It had a purge line, a rotameter and a regulator. With the nitrogen on top of the flammable materiel, no fumes would ignite.

01-06-2006, 10:41 AM
I speculate if any of the Spontaneous Human Combustion stories - once you filter out the "other know cause" ones - could be due to body oxidation processes gone all bad at once... Mostly, I see SHC poo-pooed in the technical community... but knowing a bit about how it all works...

David... There are some manly stories there that would filter us normal sorts completely out of the gene pool... Fun with propane, Liquid Nitrogen, and Magnesium should have filtered me out a time or two, for sure.


01-06-2006, 11:55 AM
As an interesting side note, it is possible to combust certain compounds with nitrogen instead of oxygen. Requires enormous amounts of heat though...still interesting!

many compounds besides halogens are also oxidizers. Infact the cathode of a battery is an oxidizing agent, except there is no combustion involved (hopefully http://bbs.homeshopmachinist.net//wink.gif )

J Tiers
01-06-2006, 11:56 AM
Early in the "X" aircraft research program they had persistent problems with LOX and the gaskets in the system. I seem to recall the original gaskets were something like leather....

In any case, they had to change them, after which no more LOX system explosions.

01-06-2006, 11:57 AM
Liquid OXygen.

01-06-2006, 11:57 AM
Could some one explain what exactly "LOX" is? Never heard of it before...

01-06-2006, 11:59 AM
Oh duh..."liquid oxygen" Nevermind, i'm an idiot!

01-06-2006, 11:59 AM
You beat me to it, Evan! Thanks though

01-06-2006, 12:03 PM
Sometimes called LO2. LN2 is liquid nitrogen. LH2 is liquid hydrogen.

01-06-2006, 12:16 PM
<font face="Verdana, Arial" size="2">Originally posted by pgmrdan:
Are you thinking of diesel engines?</font>

No. Actually I was thinking of early rocket experiments, by the germans. If I recall correctly Hydrazene and Oxygen will spontaneously ignite. Or maybe it was Kerosene? I don't remember.

01-06-2006, 12:56 PM
Actually it's hydrazine and nitrogen tetroxide. They use it in the shuttle thruster system. Hydrazine and nitric acid work too.

Then there's T-Stoff and C-Stoff which are combination bipropellant hypergolic fuels.


Looking it up T-Stoff (the Germans) is hydrogen peroxide, water and some small amounts of other chemicals. C-Stoff is methanol, hydrazine hydrate, water and "catalyst 431" (K3Cu(CN)4)

[This message has been edited by Evan (edited 01-06-2006).]

01-06-2006, 02:53 PM
All sorts of great possibilities. Aerozene 50 (even mix of hydrazine and unsymmetrical dimethylhydrazine) and nitrogen tetroxide in the Titan boosters, nitric acid and kerosene in the Scud A, unsymmetrical dimethylhydrazine and inhibited red fuming nitric acid in the Scud B. All work much the same - spontaneous decomposition when mixed, and no ignition system needed.

None are common household chemicals, except the kerosene.

I suspect the original questions is an overinterpretation of a safety warning - much like "all guns are loaded". Of course it's false, but you might actually reach retirement age if you treat it like it's true.

01-06-2006, 06:24 PM
Another neat one is Silane. (SiH4)

When it burns you get Silicon-dioxide (sand, only in a very fine powder) and water.

Silane is a pyrophoric gas in that it burns on contact with air, no other ignition source needed.

It is also unique in that under the right conditions, it can collect in closed places (most notably under the eaves of the open-sided shed the bottles are kept in -- and explode.

I'm just finishing up a semiconductor cleanroom project at work and the stuff is downright dangerous. (...but still not one of the most dangerous gasses used in making semiconductor chips.)

More info on this one can be found at:


01-06-2006, 06:42 PM
<font face="Verdana, Arial" size="2">Originally posted by dvideo:
I speculate if any of the Spontaneous Human Combustion stories - once you filter out the "other know cause" ones - could be due to body oxidation processes gone all bad at once... Mostly, I see SHC poo-pooed in the technical community... but knowing a bit about how it all works...

David... There are some manly stories there that would filter us normal sorts completely out of the gene pool... Fun with propane, Liquid Nitrogen, and Magnesium should have filtered me out a time or two, for sure.

--jerry </font>

A customer of mine services breathing equipment for people will heart/lung disease.Ever see some of the folks that have the traceha tube for the're breathing air?He said one of the common bad habits for some of the lifelong chain smokers is to smoke while breathing oxygen through the tube.He said more than few have been found dead with the're lungs roasted because they took a drag on a non-filter cigarette.Aparently all it takes is a small ember being inhaled,but oh well they were in the process of killing themselves anyway.

01-06-2006, 06:48 PM
When I was younger I was welding a truck frame. I saw flames reflecting in my hood before I felt the heat on my back. I was wearing a leather cape and sleeves but my tattered t-shirt was visible from behind. After ripping the burning shirt over my head I turned to see a wide eyed fellow worker holding a torch with eyes like saucers.

He say, "I didn't have the torch lit, I just blew some of the air in that hole in your shirt". His lesson learned at my expense.

01-06-2006, 07:11 PM
<font face="Verdana, Arial" size="2">Originally posted by pgmrdan:
a lance being used to apply only oxygen to an initially heated piece of steel. It talks about piercing steel several feet thick using this method. The lance is a consumable hollow metal tube that can be several feet long and only delivers oxygen.</font>
Thermal lance? Popular for gaining access to vaults I understand .
Hydrazine. We had plenty of this stuff at the power station. It was metered into the boiler feedwater as an oxygen scavenger. I remember one guy decided he was going to take some home to give his car some extra boost(he had heard that it was used as rocket fuel by the Germans); put some in a bottle and on the way home he had to sniff it didn`t he. Instant nose bleed and collapse; he was lucky? and stupid.
We had a large spill of the stuff one time.
"sand bag it and wash it down the drain boys!" Bastards! they didn`t give a flying f.. for health and safety. There was plenty of blue,brown and white asbestos at that plant as well, not to forget the PF either.
Man, you want to see that go when the oxygen, fuel ratio is correct and it finds an ignition source...Kaboom! !


[This message has been edited by speedy (edited 01-06-2006).]

01-06-2006, 07:37 PM
Some of the old time top fuel guys would dump a little hydrazine in with their nitromethane until it was quickly outlawed for numerous safety concerns.


<font face="Verdana, Arial" size="2">Mixing Nitromethane(an oxygen-rich industrial solvent used in the
printing industry to clean printing presses and in motorsports,
especially drag and sprint car racing as a racing fuel) and
Anhydrous Hydrazine(a compund used in rocket fuels) creates a
highly explosive and *very* unstable mixture. Back in the mid to
late '60s, there was a lot of experimentation with this mixture to
create horsepower in drag racing engines. While the amount of
horsepower created was not what people were hoping, there were
many problems with unintended effects, i.e.:explosions that tore
the front off of the Top Fuel Dragsters when they would land hard
after launching into a wheelstand, a rather common occurance in
the dragsters of that era. Seems that not only was the mixture that
unstable, but the mixture created crystalline deposits that built up
on the inside of the front-mounted fuel tanks. These crystals were
said to be very, very unstable and explosive.

Well, the National Hot Rod Association, being very safety-minded,
outlawed Anhydrous Hydrazine as a fuel additive after a few of
these little accidents.</font>

[This message has been edited by Carl (edited 01-06-2006).]

01-07-2006, 10:54 AM
Have you ever seen a loading dock for the LOX. Next time you see one like at a Hospital, notice that there isn't any asphalt around it. LOX will cause spontaneous combustion if it hits asphalt. One of the worst firse I have ever been to was when a LOX truck sprung a leak and caused the asphalt to burn. It is an oxidizer, that the way it is listed in the book and must be placard as such.

01-07-2006, 09:08 PM
Having spent the most wonderful 9 months of my life working in a steel mill, I remember a coworker using an oxygen lance to cut some steel slops up. He took a small board off of a scrap pallet laying nearby, set it on the ground and placed a lump of coal on it. He used a wooden match, lit it and placed it upon the scrap wood, took the lance which was a peice of 1/8" pipe and turned on the oxygen very slowly. The wood caught fire and when it was going good he moved the lump of coal into the fire, got the coal going and heated up the pipe to red with it, more O2 and pipe started to burn. Then over to scrap steel and started cutting. Whole process took about 5 minutes which is about how long it took me to type this.Had a calender showing an 8' thick peice of steel being cut with dual regulators with dual hoses on each regulator. Wonder how wide the kerf was?

[This message has been edited by mcostello1@msn.com (edited 01-07-2006).]