Blowing air on fire gives me two different results

Question

I know why blowing on a candle extinguish the flame from here.

But then, why does blowing on smoldering coals cause them to burn brighter?

Answer 1

While blowing on a flame removes the gaseous fuel (vaporized wax) from where the most heat is generated, you cannot achieve the same for charcoal, because charcoal is solid. Unless you blow so hard that charcoal pieces fly all around the place, the (solid) fuel stays where most of the heat is. Plus, the remaining oxygen from your breath and the fresh air that is entrained with it, cause it to burn brighter because, due to physical obstruction, it is difficult for a heap of charcoal to get enough oxygen to burn optimally. That is also the reason why you should never operate a charcoal grill inside a closed room, unless you want to die from carbon monoxide poisoning (incomplete combustion).