Sea survival and is oxygen flammable???

[dralex]

I went to Poole last week to do my 3 day sea survival training, so am now have a basic first aid cert( /forums/images/graemlins/confused.gif), personal survival techniques and also fire fighting. Having done the jump, swum around the pool infull oilies, getting into a liferaft and spending 45 minutes in it, I would hate to ever have to spend more time, especially at full occupancy.The storm simulation was better then I anticipated. It definately proves the adage- stay with your hull for as long as possible.

On the fire fighting, one of the instructors swore blind oxygen is flammable in high enough concentrations. I always thought that despite strongly supporting combustion, O2 was NOT flammable. DOes anyone have evidence to prove either argument??

Lots of video clips of Americans being STUPID, eg fire fighter called Chuck blowing himself up, the classic one about USN Aircraft Carrier v Lighthouse etc.

On balance, a very good course. I remember the arguments about the RNLI training college, but having been there now, it gets my vote.

 

[Evadne]

Er, I always thought that the definition of being flammable was that it burns in the presence of oxygen. (Wierd chemistries not found on this planet being excluded.)

I do know that some things will spontaneously ignite if the oxygen concentration is high enough, which may be what they mean, and putting oxygen onto a fire is very dramatic, but if you have heat plus oxygen but no fuel, you can't have a fire. You need all three components.

 

[FullCircle]

I always thought Oxygen is a combustion promoter. After all, I put Nitrous Oxide on my motorbike to increase the pure Oxygen levels from 21% (atmosphere) to 36%. This has a instant (and large) effect on combustion, and thus power output. Fuel load remains the same, so the resultant is an increase in the efficiency of the combustion process.
The extra heat generated (bit like a blowtorch) builds up very quickly.
No different from fanning glowing embers to get them to burst into flame. In other words, you need to have an ignition source and a fuel. I think. /forums/images/graemlins/blush.gif

 

[Blue5]

[ QUOTE ]
On the fire fighting, one of the instructors swore blind oxygen is flammable in high enough concentrations. I always thought that despite strongly supporting combustion, O2 was NOT flammable. DOes anyone have evidence to prove either argument??

[/ QUOTE ]

The instructor is right in concentrated form (cylinder) it is highly explosive and if transported on cross channel ferry it is classed as dangerous goods.

 

[dralex]

But surely it must still have a fuel to combust, even for an explosion, otherwise it would just be rapid expansion of a compressed, liquefied gas. Ther must be some other element to burn, eg a small amount of grease.

 

[oldharry]

I agee with Dave White: The 'triangle of combustion' requires the presence of Fuel, Heat and Oxygen for combustion to take place. The principle of fire fighting is to remove one of these three components: Remove the fuel and however hot oxygen gets, there is nothing to burn. Correspondingly, the fuel can not burn if the oxygen is removed - which is often what fire extiguishers are designed to do.

The problem for Cross Channel ferries and airlines is that in a fire situation suddenly adding a large quantity of oxygen has devastating results.

 

[Eightball]

hi yes itr can under presure had instant where plane oxy bottle sprung leak some how blew plane to bits .also you dont put oil or grease on any o rings on oxybottles as it is suppose to blow if you open vale never tryed it .but thats what we were told on our oxy rebreathers mined thats a long time ago ?? dave

 

[dralex]

All O2 valves are greaseless and have stickers on saying use no grease- the grease will act as the fuel.

 

[AlienP2]

I remember school boy chemistry lessons when the test for oxygen was to insert a glowing splint into the test tube. In the presence of oxygen it re-ignites. However, it is the splint that is burning (ie providing the fuel).

The 'pop test' for Hydrogen was always more fun although it required the splint to be burning rather than just glowing.

 

[sighmoon]

I think if the oxygen is in very high conentrations, it makes fuel out of things that wouldn't normally be combustible enough to be a hazard.

 

[dralex]

That sounds logical.

 

[VicS]

[ QUOTE ]
I think if the oxygen is in very high concentrations, it makes fuel out of things that wouldn't normally be combustible enough to be a hazard

[/ QUOTE ] Thats right.
It does not require a great deal of oxygen enrichment of our normal atmosphere (approx 21% oxygen) to make things which are normally flammable violently so and many things which would not normally be flammable will burn in high oxygen concentrations. For example one of the standard school chemistry demonstrations is to heat some steel wire wool to red heat and plunge it into a gas jar of oxygen. It then burns quite vigorously.

Oxygen, or any thing that can produce oygen when heated, in a fire situation is, for these reasons, a serious hazard but it is not correct to call oxygen a flammable substancce in the normal sense of the word. Firefighters would however treat oxygen as though it were flammable.

 

[cindersailor]

Conventional burning is simply the exothermic (heat releasing) reaction of a combustable material with oxygen. Almost anything containing carbon will burn to release energy in the presence of oxygen if sufficient energy to initiate the reaction is provided (spark, flame etc.). Many metals are also very good at burning in oxygen because they form very stable oxides. The reason for this is that the mixture of combustable material and oxygen is thermodynamically unstable with respect to the products (carbon dioxide and water in the case of hydrocarbons, wood etc.); however there is an activation barrier to overcome before the reaction can start. Hence combustable materials do not spontaneously catch fire when exposed to oxygen. However, pure oxygen is hazardous as when you increase the oxygen concentration above the 21% found in air the combustion is that much more vigorous as it can happen more quickly.

One of the most spectacular demonstrations of this is to dunk a digestive biscuit into liquid oxygen and then set fire to it (do not try this at home, even if you can invent a way to produce liquid oxygen in your kitchen!). It burns with a very bright and hot flame and very quickly. Try this in normal air and it will just smolder and then go out. Other interesting properties of liquid oxygen are that it is blue and is attracted to a magnet!

The reason why gas cylinders in general (including oxygen) are considered hazardous is that they contain very high pressures and if they fall over and get the valve knocked off will resemble a torpedo.

Chemistry lesson over!

 

[benjenbav]

Just out of interest, will you be pinning up the first aid certificate on your surgery wall?

 

[dulcibella]

Definitely not combustible - schoolboy howler!

 

[dralex]

/forums/images/graemlins/grin.gif It had crossed my mind!

I think the consensus is- NOT FLAMMABLE.

I'll take great pleasure in e mailing him.

 

[Rowana]

I used to work with a Blacksmith whose party piece was to take an oil can and put a splodge of oil on his anvil. Next, take the oxy-aceteline (sp?) torch and turn on just the oxygen. play jet of pure oxygen on the oil and suddenly it would catch fire.

Oxygen itself is not flamible, but in strong concentrations can make things burn in spectacular, and sometimes explosive, fashion.

 

[DJE]

[ QUOTE ]
I think the consensus is- NOT FLAMMABLE.

[/ QUOTE ]
I think it's NOT FLAMMABLE; BUT BLOODY DANGEROUS IN A FIRE!

 

[bbg]

My understanding (and I am not a chemist) is that a fire is an oxidation reaction. Fire requires oxygen, heat and fuel. The problem is that pure oxygen will accelerate the reaction - i.e. a fire becomes much more intense. The second problem is that if oxygen is released from pressure in an uncontrolled way, the releasing of pressure can cause enough heat to start a fire, which is very easy to do in an oxygen rich environment.

Before anyone jumps on me about the fact that gas COOLS when it is released from pressure (which is true), I am talking about the friction of the gas passing at very high speed through an unregulated opening (i.e. a hole), for example.

If an oxygen tank or hose ruptures, you almost certainly have all three components of a fire - the oxygen, the heat (caused by the friction of release), and the fuel (the hose, tank, or any contaminants on either hose or tank). Bang.

As to whether oxygen is flammmable, this might be a bit of semantics. In the oxidation reaction, perhaps one could say that technically both components of the reaction are contributing, therefore both are flammable. But saying that oxygen itself is flammable "in high enough concentrations" is bollocks - as proven by the fact that it is possible to contain 100% pure oxygen, even pressurised, without there being a fire. I am not aware that it is possible to have a concentration above 100% - but I am told I have been wrong before.

(Ducks, awaiting a chemist to tell me I am full of shite.)

 

[peterb]

There was a time (some years ago) when I was convenor of the ISO committee dealing with fire terminology. Combustion was defined as:

"Exothermic reaction of a substance with an oxidizer."

As far as I know, there is nothing that can oxidize oxygen.

Flammable was defined as:

"Capable of flaming under specified conditions."

Flaming was defined as:

"Undergoing combustion in the gaseous phase with the emission of light and heat."

The whole vocabulary of terms was drawn up as a tree structure. Any term found in a definition and which itself had been defined was shown in bold, so that the definitions could be traced back to a few carefully defined roots which would be independent of the fire field. "Combustion" was one of the root terms. You can see that under these definitions oxygen can only be considered as "flammable" if it is burning in a fuel-rich atmosphere such as methane or petrol vapour.

Oxygen-rich atmospheres can certainly produce much fiercer burning. In a reaction between oxygen and a fuel the heat release is almost proportional to the amount of oxygen burnt, with very little dependence on the type of fuel. Normally the atmospheric nitrogen acts as a coolant; the heat release has to heat the nitrogen up to flame temperature. Increasing the proportion of oxygen increases the heat release whilst simultaneously reducing the amount of nitrogen to be heated, thus giving a much hotter flame. That's why carbon dioxide, nitrogen, or any inert gas make good extinguishants.