Stupid question: Why does shaking a match put it out?
If you move a match slowly, nothing happens. But it you shake it violently, it will extinguish. By shaking it aren’t you simply increasing the flow of oxygen to the fire?
What about forest fires? Do high winds spread or kill the fire?
I suspect that by shaking the match vigorously enough, you are actually cooling the matchhead faster than combustion can heat it, and once the temperature passes below the ignition temperature, combustion ceases.
A match or candle flame is not a “point source,” but involves different areas of different effects. You’ve got the fuel – the match-stick, and the path of the air, drawn up from below, and the different areas of different temperatures. When you shake it, you disrupt these patterns, breaking them up, and destroying the process.
I think that a really good stiff wind could snuff out a grass fire burning in very short grass. Alas, once you get up to forest fires in dry pines, no natural wind is fast enough to puff it out.
Trinopus
I agree with what Trinopus said on the forest fire. For example, you can blow out a candle (or maybe even a small fire), but blowing on the fire in your fireplace will do nothing.
Actually, a better analogy would be you can’t blow out your fireplace by pointing a box fan into it. You probably would succeed in spreading the fire.
When wood is heated, it releases combustible gases and vapours; the flame is these vapours in combustion; when it is allowed to burn normally, the heat from the flame causes the release of more combustibles and the whole thing supports itself, at least until the fule supply runs out.
By blowing the match (or waving it around, which amounts to the same thing - rapid air flow, you are rapidly removing the burning vapours and gases and preventing them from heating the remaining wood, furthermore, you are quite possibly rarefying the mixture to a point where combustion would not be supported.
It ought to work for larger fires too, except that I think it will probably get progressively more difficult (at a non-linear rate) depending on the size of the burning object(s)
I think that the preferred method of extinguishing an oil well that was set aflame was to blow up an explosive right next to it. The shockwave would blow the fire out; the challenge was keeping it from relighting on the still-hot debris.
I remember knocking a candle over, panicking that it would set the tablecloth on fire, then being relieved that it had been extinguished by the rush of air from the fall.
Another difficulty with blowing out a large fire is that you need to blow the fire away from all of the fuel. With a match or candle, or indeed, an oil well, the fuel is pretty well localized. But if you blow a forest fire away from this section of the forest, you’re just blowing it over to that section of the forest, where there’s still stuff to burn.