Eli5: Why when you blow a little “wind” on a candle it will blow out? But very strong winds are known to increase the size of wildfires and make them spread more easily?

Question

You would think the more wind the faster the fire gets extinguished, I have a feeling the size of the fire matters but i just wonder why and where the line is drawn between a candle and a wildfire in extinguishing it when blowing wind on it goes from a very effective to a super ineffective technique.

In: 0

Answer 1

If the wind is less than what the fire can heat then the wind will make the fire hotter because it introduces more oxygen (fire is rapid oxidation). If the wind is more than what the fire can heat, the burning fuel will cool off until it drops below its combustion point and it goes out.

What this means is a little fire like a candle can only handle a little tiny wind before it will cool faster than it can heat and goes out. A big fire can handle a big wind and will take a massive wind to cool it faster than it heats and go out. Once the fire is big enough, nothing is going to generate a wind fast enough to exceed the speed at which it can heat the fresh air.