Why can you blow a small flame out?

[chunhon]

When you blow a small flame(e.g flame of a candle), it can go out. Wouldn't the extra oxygen help the flame blow bigger.

[insane_alien]

when you blow on a small flame you cause it to lose too much heat. when it loses enough heat the reaction stops and it goes out. on bigger fires this isn't a problem as the reaction is producing much more heat.

 

the CO2 in your breath also helps extinguish it.

[the tree]

I think typically your breath contains less oxygen than the surrounding air, on account of you've just been absorbing it.

[insane_alien]

yeah but its mainly the extraction of heat. A lot of non breathed air gets mixed in with your breath as you blow so the CO2 effects are reduced somewhat especially if you are blowing from a distance.

[gcol]

The harder you blow, the bigger the flame you can put out. Think of how high explosives are used to put out oil rig fires. And in that case there is no doubt that the explosion removes all oxygen.

 

Perhaps even a megablast of pure oxygen, really cold, would extinguish a flame by lowering the temperature of the combusting substance below its flashpoint?

[timo]

I'd also assume it's the heat that is blown away that stops the flame. I really doubt that the CO2 in the breath air has any measurable effect:

- Why should CO2 have any effect at all?

- Since what you probably meant was "the lack of O2 in your breathing": There´s quite a lot O2 in the air you exhale. That's one of the key points why CPR works.

[YT2095]

actually a draft from a fan will blow a flame out, Breath CO2 isn`t the answer, it`s pure Heat removal, and in some cases Fuel removal by over dilution with air making it no longer combustible as a mixture.

[gcol]

I wonder if one of those bombs that initially produce a fine mist of combustible material which is then ignited, thus removing all oxygen from the vicinity would also extinguish most fires. An extreme example of fighting fire with fire?

[YT2095]

it`s more than just a mist that`s Ignited, setting fire to it doesn`t work, it needs a detonation charge to be an effective FAE.

[gcol]

Yes, I know that. Pedantry rules, O.K?

 

Moving on.....consider two different types of flame, a candle and a bunsen burner. The candle requires heat (from its own flame) to melt the wax, and oxygen. Once ignited, the bunsen requires only heat, the oxygen pre-mixed with gas. Bunsen o.k. in vacuo, candle not. Therefore different extinguishing methods for different flames.

[YT2095]

no, force more Air into the FA mix even on a bunsen and it will go out.

the ratio is wrong.

[gcol]

Ah, even more pedantry. You are on a roll! Might just as well say sprinkle borax on the candle flame or spit on it.

 

So how many ways to put out a flame? possibly as many as there are combustible combinations. Moral, dont hang your arse too near the fire. If you do, fart really strongly.

[YT2095]

so it`s a Good Post if it supports you, and "Pedantry" if it corrects you?

Fascinating!

 

either way, stop being silly and Remember the old Primary School "Fire Triangle" that you were taught.

[Klaynos]

There are 3 ways to put out a fire as all children know.

 

Remember your fire triangles kiddies... ;P

[gcol]

Old hat. Now supercede by the Fire Tetrahedron Look it up. If I try to explain it, a certain person having a bad-hair day will surely nitpick.

[Klaynos]

Ok then four, whoopty doo..

 

Kids are still taught the triangle though. So popular knowledge goes for the triangle, and as this is talking about blowing, unless you have some very very strange exhaust fuels I don't think the reaction component is important.

[the tree]

You can put out a small candle using a lighter, and light the lighter without sparking in the process, this gives the illusion that the flame is moving from the candle to the lighter and it makes for a good party trick.

 

(by good I mean amusing, once, not really worth it though)

[chunhon]

Thanks people

[spooky]

 

Thought this just might clear a few things up ^.^ I remember trying to teach the cub scouts (9-12 I think), how to light fires and maintain them and all that...was pretty difficult.....

[frostbite]

yes, i guess its more on the heat removal rather than drowning it with CO2. your breath is at a lower temperature than the flame. your breath gets some of the heat from the flame. and this action makes the fire triangle or fire tetrahedron crumble.

[Rocket Man]

just dont over-heat a tea light candle and expect to blow it out.

you can get one of those candles in the little aluminium tins to reach flash ignition point before they reach boiling point.

 

don't toss water on an oil fire.

it's got plenty of primed combustibles and ready heat than water can remove so as the water boils, it exposes more flaming wax or oil to the air allowing a faster combustion.

[YT2095]

the best thing to do in some Oil fires (like a Chip pan fire in a kitchen) is add more cold oil if you can`t cover the fire!

 

 

use water and you`re Royally Screwed!

[the tree]

the best thing to do in some Oil fires (like a Chip pan fire in a kitchen) is add more cold oil if you can`t cover the fire!

I get how this works in the case of oil rigs, but can you really add that much oil that quickly to a chip pan?

 

Either way, I'd still be extremely tempted to just throw it out the window, partially because that'd cut out two elements of the fire triangle (fuel and heat) and also because I've always kind of wanted to defenestrate a metal bucket of fire for some reason.

 

I'm yet to meet a tea-light that I can't put out with my breath or hands.

[insane_alien]

just throw a damp tea-towel over the chippan as long as it doesn't touch the oil or drip then its fine. starves itself of oxygen pretty quickly.

[YT2095]

I get how this works in the case of oil rigs, but can you really add that much oil that quickly to a chip pan?

 

Either way, I'd still be extremely tempted to just throw it out the window, partially because that'd cut out two elements of the fire triangle (fuel and heat) and also because I've always kind of wanted to defenestrate a metal bucket of fire for some reason.

 

yes, it`s all about lowering the overall temp below the flash point, it goes out on its own, the trick is NOT to panic, just stay cool and pour.

Bicarb is also good to add for smaller kitchen fires.

 

now the "throw it out the window" is a Class A act of utter Stupidity, are you REALLY going to try and carry this?

imagine some sloshes over and gets on you leg, YOU are now a candle!

the viscosity is almost that of water at these temps also and the flames are high and large and HOT! the draft from an open window can shove those into your face!

 

NO, you leave it Exactly where it is, you NEVER try to move it! remove the heat source (unplug or turn off the heater), if you Don`t have a way to cover it (and you should) then pour in more oil!

 

Capiche?