OT: Oxygen catching fire?

[Davey]

From the Telegraph:

"EgyptAir flight MS804 was travelling from France to Egypt in May 2016 when it crashed into the sea south of Crete, killing everyone on board the Airbus A320. Among them were 12 French tourists, a Briton, 30 Egyptians, two Iraqis and a Canadian.

The Egyptian authorities claimed at the time that the plane was brought down by a terrorist attack ? despite no group ever claiming responsibility.

But an official investigation has concluded that it was caused by a cigarette being smoked in the cockpit that inadvertently ignited oxygen leaking from an emergency gas mask. "

I thought that oxygen assisted combustion, but was not itself flammable. It sounds like another case of somebody not knowing their science, but that somebody is "The Official Investigator", who produced the report.

[Jeff Gaines]

You're right, odd finding. wonder if anybody will point out the problem?

[Martin Brown]

Serious fire accidents resulting from an oxygen rich atmosphere are rare but can be incredibly serious. A zone of pure oxygen will turn a smouldering cigarette into a raging inferno and potentially ignite anything else inflammable nearby like bits of cockpit plastic and pilots. This was the mode of failure of the infamous Apollo 1 test.

Hospital patients sneaking a quick drag on a cigarette in an oxygen tent sometimes end up on fire too. Things are even worse if they have one of the fat based skin creams being used at the same time.

Pure oxygen can make things remarkably volatile. I suspect the report may have lost something in translation.

More likely that it was the cigarette flame that ignited the leaking oxygen mask creating a very quickly accelerating conflagration.

LOX & cotton wool or LOX and rich tea biscuits are a staple of spectacular pyrotechnical RSC chemistry lectures. eg.

There is a video of the guy who used to do this trick with a red hot iron bar to detonate the LOX & cotton wool demo with a plaster on his forehead later in the sequence (he scaled it up slightly for filming).

I think that variant has now been banned as too dangerous for modern health and safety. I have seen him bring ceiling tiles down with it and small fragments of sensitised gun cotton land on the floor afterwards.

Gas suppliers refused to sell him LOX after he retired so he built his own portable LOX still powered by LN2 (which any decent lab has).

[The Natural Philosopher]

I think it is you who does not know their science - forget the journalist - an oxygen full cockpit makes everything inflammable.

[Nick Odell]

That's the Telegraph journalist speaking, not the official report. The article also says that the official report has yet to be publicly released.

Nick

[Colin Bignell]

You are quoting from a newspaper report. It is never safe to assume that a newspaper report is a factually accurate account of what is being reported. The term oxygen fire is widely used to describe any fire that is due to the presence of enhanced levels of oxygen. The reporter may not have understood that, or there may have been a mistranslation from the original report.

[Harry Bloomfield Esq]

The Natural Philosopher brought next idea :

Even steel can burn, given enough of an oxygen supply. Wire wool pan scrub pads can be made to combust, in air.

[Jeff Gaines]

Indeed, that's what the OP implied and I said. Oxygen on its own is not flammable.

[Clive Arthur]

Oxygen will burn in, for example, a methane atmosphere. I seem to recall that being demonstrated at school on a bell jar, probably with town gas.

It's the interface between the constituents where they react vigorously which is where the flame is.

[Of course, in your example, the journo probably just made a mistake.]

[Spike]

Before the Apollo fire, a Ukrainian-born trainee cosmonaut, Valentin Vasiliyevich Bondarenko, was killed in a fire in a 50% oxygen-rich low-pressure training exercise on Moscow:

"23 March 1961 was the tenth day of a 15-day endurance experiment in a low pressure altitude chamber at the Institute of Biomedical Problems in Moscow.[4] The chamber's atmosphere was at least 50% oxygen. Bondarenko, having completed work for the day, removed monitoring biosensors from his body and washed his skin with an alcohol-soaked cotton ball, which he then discarded. The cotton ball landed on an electric hot plate which he was using to brew a cup of tea. The cotton ignited and Bondarenko tried to smother the flames with the sleeve of his woolen coveralls, which caught fire in the chamber's oxygen-rich atmosphere.

Because of the pressure difference, it took a watching doctor nearly half an hour to open the chamber door. Bondarenko's clothing burned until almost all the oxygen in the chamber was used up and he had suffered third-degree burns over most of his body. The attending physician at Botkin Hospital, surgeon and traumatologist Vladimir Golyakhovsky, recalled in 1984 that while attempting to start an intravenous drip, the only blood vessels he could find for inserting a needle were on the soles of Bondarenko's feet, where his flight boots had warded off the flames. According to Golyakhovsky, cosmonaut Yuri Gagarin spent several hours at the hospital as "deathwatch officer". Bondarenko died of shock 16 hours after the accident, less than three weeks before Gagarin's first spaceflight aboard Vostok 1.[5] Manned orbital flight program director Nikolai Kamanin blamed Bondarenko's death on the Institute's poor organisation and control of the experiment.[4]

Bondarenko was buried in Lipovaya Roshcha in Kharkiv,[6] where his parents were then living. On 17 June 1961 the Presidium of the Supreme Soviet posthumously awarded Bondarenko the Order of the Red Star."

[Chris Green]

Surely the idea of X burning in Y is no different from Y burning in X.

Burning is just a hot chemical reaction producing a flame. The idea that "oxygen can't burn" doesn't really make sense. You could say exactly the same about almost anything. "Hydrogen can't burn" if there's no Oxygen present. Whether "Hydrogen burns in Oxygen" or "Oxygen burns in Hydrogen" is impossible to define really. It's just that, generally, in the world we are familiar with we have an oxygen rich atmosphere in which other things burn. If our atmosphere was (say) methane rich then things might burn in methane (including oxygen).

[Jeff Gaines]

The position relating to oxygen and burning has been known for many years.

[Colin Bignell]

A local concentration of 24% or more oxygen is enough to make most things combust readily.

[Martin Brown]

It can be somewhat different since there is an excess of the major component that the other being injected into as "fuel".

But it is only really by convention because we happen to live in an oxygen rich atmosphere. On Saturn's moon Titan it would be exactly the other way around - oxygen would burn in it's methane rich atmosphere.

There are subtleties too in zero g. The flame quickly becomes diffusion limited with no gravity to move the hot combustion gasses away.

Playing with flames in zero g has opened up new areas of research into how flame reactions behave under more easily controlled conditions.

Also they are aiming to figure out how to extinguish an unwanted fire safely in a space station without also seeing off the astronauts.

There oxidisers even more potent than oxygen most notably ClF3 or as the Germans called it N-stoff. Elemental fluorine is tame by comparison.

Rather nice picture of a wine glass on fire.

[Steve Walker]

Normally, burning is defined as a process of oxidation, so hydrogen can burn in oxygen, but even when the other way around, it is the hydrogen that is being oxidised at the interface between them.

However, using the term oxygen fire is quite normal for cases where items that do not readily burn in air, do so vigorously in oxygen rich atmospheres.

[Tim+]

If this was a low pressure test this doesn?t make sense. There?s very little risk from increasing the ambient pressure quickly (unlike dropping from a higher pressure). I suspect the delay was cause by panic and confusion about the risks.

If it was a hyperbaric chamber then one might worry about the effects of decompression but I reckon the consumption of oxygen by the fire would have dropped the pressure rapidly anyway!

Tim

[Spike]

It was to have been a 15-day isolation test for Bondarenko, using a reduced-pressure atmosphere enriched to 50% to make it breathable.

I guess the pressure rose with the addition of the combustion gasses more than making up for the decrease in oxygen content. The picture I've seen of the chamber - which was quite small, say 6' x 10' - had an outer-opening external door to a tiny vestibule leading to the test chamber itself, just big enough for a chair and tiny work surface, say

5' square. The inner door appears to open inwards and it may be this one that they couldn't open straight away perhaps due to the pressure of the combustion gasses.

[Martin Brown]

The heat generated by combustion generally makes the pressure in a sealed pressure vessel rise very rapidly indeed. Unless there was active pumping to maintain the low pressure the chamber would be over pressure.

If it was burning pure carbon completely then

2 C + 2 O2 => 2 CO2 + heat = no change in number of molecules

When the oxygen starts to run out then

2 C + O2 => 2 CO = number of molecules doubles

Actual results will be in between with an additional small contribution from any hydrogen from olefin plastics as steam. The increase in temperature from the fire makes all the difference.

The technique is called bomb calorimetry. You put a measured amount of fuel in with pure oxygen, seal it up tightly and ignite. The heat of combustion can be measured and used to determine calorie content.

They have used this method on many building materials after Grenfell - but sadly it answers the wrong question and fails just about everything as "Flammable" that isn't already an inert refractory oxide material.

It doesn't distinguish between something sufficiently fire retardant to merely smoulder at 1cm/minute and the napalm loaded plates that that they strapped onto Grenfell with a burn rate of 2m/minute.

Burning in pure 100% oxygen at constant volume they both burn in a matter of a seconds or less as the internal pressure rises very quickly.

[Theo]

Also different states/media. It makes sense to talk about burning wood in (gaseous) oxygen, but not much sense to about burning oxygen in wood (how would you get it inside? How would you ignite it?).

Chemically it's the same, but physically it's different - surface area, mixing, etc.

After all, everyone knows that petrol burns in air. Exactly *how* to burn petrol in air has taken a century of development.

Theo

[brian]

In message <t4av9d$395$ [e-mail], Davey [e-mail] writes

Sounds like obblocks . Everyone knows combustion is caused by phlogiston.

B