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This sounds like a stupid question perhaps, but if a stream of pure $\ce{O2}$ was directed at the flame as a concentrated jet would it blow off the candle?

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  • $\begingroup$ I think that the opposite will probably happen. Since flame is the direct result of a combustion and oxygen gas is a reactant on the reaction, adding more to the flame would instantly increase the rate at which the combustion will occur. $\endgroup$ – Kent de los Reyes Sep 16 '19 at 3:42
  • $\begingroup$ and quora.com/… $\endgroup$ – Nilay Ghosh Sep 16 '19 at 5:36
  • $\begingroup$ Not possible. See this video $\endgroup$ – Nilay Ghosh Sep 16 '19 at 5:36
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    $\begingroup$ @Nilay Ghosh But, should not the same reasoning work for air too ? Perhaps for oxygen the needed flow is much higher. At some point. it would cool down the candle enough and decrease the partial pressure of parafine enough to extinguish the flame. $\endgroup$ – Poutnik Sep 16 '19 at 5:50
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    $\begingroup$ By other words, what happens if oxygen flow speed overtakes the speed of the flame propagation ? Also, note that the geometry of the candle in the video plays for keeping the flame. If the candle were a tall one with pointy end and exposed knot, it could be different. $\endgroup$ – Poutnik Sep 16 '19 at 7:08
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It depends on the wick. A flammable wick, exposed to oxygen, will burn, but a non-flammable wick, saturated with liquid wax, could be chilled by the gas flow, and when the evaporated wax is blown clear of the wick, the candle flame could extinguish for lack of fuel. Basically, the oxygen flow might (at sufficiently high velocity) remove the vapor fuel so that the flame becomes a detached fireball, and the wick and wax of the candle cool. The oxygen flow just has to be faster than the flame propogation in the fuel-oxygen mixture.

A solid flammable wick, though, won't be displaced, just burn faster, and on discontinuing the oxygen, the candle will still be lit.

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  • $\begingroup$ What is a solid flammable wick? A stream can cool down in principle every wick. At least it coukd extinguish the flame and perhaps the wick keeps being slowing and superficially oxidised. $\endgroup$ – Alchimista Sep 16 '19 at 9:28
  • $\begingroup$ @Alchimista A solid (cotton string) wick in a gas stream holds a boundary layer of stationary gas at its surface, unless we're talking about highly turbulent (or supersonic) flow. The combustion of the cotton (which makes the top of a candle wick blacken and turn to ash) is much slower than the combustion of the evaporated candle wax, but an oxygen flow can change that. $\endgroup$ – Whit3rd Sep 16 '19 at 19:08
  • $\begingroup$ Sure. You mos likely help the burning of the boundary layer but still you could blow it out. The Wick burning is basically the same as wax burning. I would say the first part of your question is correct. Anyway we all more or less understand the same. Blow enough fast and one might blow out a candle even with oxygen. $\endgroup$ – Alchimista Sep 16 '19 at 21:06
  • $\begingroup$ @Alchimista - in the case of a steel plate being cut by oxyacetylene, the cut, once started, can be completed on pure oxygen, turning the acetylene off. The flow of oxygen impinging on hot burnable steel doesn't cool it, it reacts with the surface layer, oxidizing with enough waste heat to liquefy the oxide and preheat the layer just beneath it... $\endgroup$ – Whit3rd Apr 14 at 6:31
  • $\begingroup$ Yes yes but you can't blow out what you are cutting. Burning and cutting something is not a candle flame. $\endgroup$ – Alchimista Apr 14 at 11:59
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Fire triangle dictates that a fire requires fuel, oxygen, and heat.

Directing a jet of oxygen at the candle will not remove the fuel, will add oxygen... so the only way for it to extinguish the candle is to change the heat (reduce it) dramatically.

If the oxygen is cold enough - perhaps from being highly compressed and decompressed rapidly to produce the 'jet' - it might cool the candle enough to make it less flammable.

But I suspect it's more likely the oxygen stream would ignite and the cylinder might explode.

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  • $\begingroup$ How would the oxygen stream "explode" ? The fuel cannot flow against the oxygen stream, and oxygen without fuel cannot burn. The flames can only exist past the point of mixture. $\endgroup$ – MSalters Nov 15 '19 at 15:53
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Easily, just need enough velocity/volume to reduce the temperature. Similar to when lighting an oxy/acetylene torch, the acetylene is turned on and lit .Then the oxygen must be added/turned on very slowly to avoid blowing out the flame.

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