FIRE PR

[Guest]

I was volunteered by her that must be obeyed, for a PR session, at our kids school, and I was surprised to asked what a fire triangle was. I duly explained, fuel, oxygen & heat was required for combustion to take place. Remove any side of the triangle and the fire will go out. One little chap suddenly piped up, “So when you blow a candle out, which side of the triangle does that remove?” For a few seconds I was stumped, I said it was removing the fuel. Then the little darling said, but surly it’s cooling. I wont go, on you get the picture; I was almost beaten by a simple candle question. School PR never again!!!

[Guest]

Surely is oxygen cos ur putting x amount of CO2 around it.  The candle being the fuel is still there.

[AnthonyB]

You don't just exhale CO2, theres still 16% Oxygen in exhaled air as oppose to 20% in room air

[fireftrm]

Cooling - the action is removing the heat from the fire. It isn't  smothering as Anthony says, nor is it Starvation - the candle wax is still there!

[Guest]

So at what temperature would a blast of hot air no longer extingiush a flame?
The fuel is the vapour of candel wax, and the flame would have to be cooled to a temperature that would not allow melting, wicking and vapourisation of the wax. If the air was hot enough to melt the wax but was at atemperature below the flash point of the vapour air mixture would the candel go out? yes proberbly, so a blast of air at a temp above the ignition temp of vapour should not extingiush the flame! ...but what if it does?

[Pete M]

Possibly something to do with the dilution effect of the air bringing the fuel (in this instance vapourised paraffin wax) / air mixture below the concentration required for 'burning'.  In other words bringing it down below the LFL of the fuel.

[Pete M]

Of course, the damned thing would most likely re-ignite once the air blast was over.

[Simon Morriss]

This is quite a question.  I think it will be removal of oxygen as the air is moving at such a rate past the flame it has no time to use it.

Someone must have done a thesis on this.

[Chris Houston]

You should have answered this like all professional presenters do when stumped:

"Well, what do you think?"
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I think that while there may some cooling, it is the removal of the fuel (vaporised candle wax) that is the key.  When the blowing stops, the heat is gone which stops the fuel being created.
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Anyway, should you not have been talking about the fire tetrahedron, you also need free radicals for fire as well as the fuel, O2 and heat.

[Guest]

the answer is in the 'MIX'

Remember the fire triangle is made up of an equal balance of the 3 elements,
get the mix wrong and the fire will not start!
therefore not enough heat to sustain combustion ?

[wee brian]

Its really not that complicated - when you blow the flame you move it away from the fuel.

Therefore you have removed the fuel from the heat or the heat from the fuel.

It only works with fire where the fuel doesnt retain much heat. Try it with a big pile of wood and it stays hot even after you remove the flame - hey presto its starts burning again.

[afterburner]

an extension to 'Guest's' question ... when Red Adair and his team put out oil well fires by blowing them up with big shock explosives how does that put the fire out?
Is it as Wee Brian says removing the heat from the fuel = cooling? Or removing the fuel from the heat = starvation? Or momentary suffocation by excluding just enough O2 to stop the combustion process?
Or should the answer be simply a clip a round the ear and an instruction to stop interrupting?

[Guest]

Alternatively, clip "her that must be obeyed" around the ear for asking you to do it in the first place.

[Guest]

Erm I have to say the candle theory has flummoxed me.  

You lot seem more highly qualified or atleast technically minded than the likes of me . I cant keep up and Im meant to be a fire safety office. Tell me is it the IFE that made you all so brainy - cos I think I need to do   some catching up  :cry:

[Chris Houston]

Maybe is is because you are a type of room:

Im meant to be a fire safety office.

 :lol:

I think the above thread proved that most of us don't have a clue about the candle thing!