Why does blowing air on a fire make it burn better?

Answer 1

In order for a flame/fire to exist there needs to be a combustible substance in the presence of oxygen and an ignition source such as a spark or another flame. When one of these three elements are missing then the fire goes out. Some people say the fire goes out when you blow on it or in the presence of wind because the fire is being deprived of oxygen. This makes no sense because your breath and the wind are full of oxygen. In fact, anyone who has some experience working with fires knows that wind and blowing on hot embers will actually cause a fire to erupt, not put it out. It erupts precisely because of an increase of oxygen near the combustible substance in the presence of a hot ember which suffices as the spark needed. When a flame is blown out, either by wind or using your breath, one or more of the three requirements of a flame is being removed. The question IS, which ones? Well we already know it's not oxygen so it must be either the ignition source, or the combustible substance, or both. This is where it gets a little complicated because once the fire is burning the flame is actually sustained by particles, molecules, and atoms that are stripped off the combustible substance by heat and released into the air. This is why the flame is always ABOVE the substance being burned whether it is a candle wick or a campfire. Heat also rises which exaggerates this phenomenon. Therefore the flame you see actually consists of the combustible particles AND the ignition source. When the wind or your breath blows on this mixture of combustible particles and flame, it pushes the mixture away from the stream of fresh particles rising straight up from the original combustible substance thereby starving the flame of combustible particles. The flame will go out in the absence of the combustible particles, one of the three required elements for a flame to exist. This is why a campfire loses its flame as the wood becomes embers; there are no more combustible particles to sustain the flame. For a candle it is mostly the wax vapor particles that sustain the flame. That's why a thin candle burns down quicker than a fat candle even though the wicks may be exactly the same. There's more wax to burn with a fat candle. As a side note, water puts out a fire due to a similar reason as blowing on it but not exactly the same. Water on the combustible fuel source creates a sticky coating that prevents combustible particles from being released into the air where they can burn. Also, temperature has no effect on whether a fire can be created or not. The water content IN and ON the fuel source is the only determining factor. So fires are much more likely during a cold dry winter than for a hot wet summer.

Answer 2

Blowing on food creates forced convection, causing the food to cool.

Basically, as your food cools, it heats up the air that is directly in contact with the food, crating a thin layer of insulation. As this air heats up, it will rise slightly and slightly cooler air will come in contact with the food, allowing more heat to transfer out of your dinner. This is called natural convection.

Basically as your hot food sits there, it gets a very thin blanket of heated air around it, which slows down the cooling process. When you blow on your food, that warm air blanket is blown away carrying away a bunch of heat, and allowing fresher cold air to come in contact with the food, cooling it faster. That is forced convection.

This is the same principal a convection oven works on, but instead of blowing fresh cool air, it blows fresh hot air, cooking items faster than a conventional oven that does not use a fan to move the hot air around.

Answer 3

Blowing on a fire increases the intake of oxygen into the combustion zone. As there is then more oxygen then before, more comburant can be burnt, which increases the energy released, i.e making the whole system hotter.

Answer 4

The movement of the air drops the pressure around the match (Bernoulli's principle), causing the partial pressure of oxygen available to sustain combustion to drop below that required to maintain a chain reaction. It has absolutely nothing to do with carbon dioxide.

Answer 5

It increases the amount of oxygen available.

Answer 6

blowing on the fire increases the O2 level and will therefore fuel the fire. This will increase the temperature and will therefore increase the reaction rate.

Answer 7

It Increases the oxygen available for the fire. Fire needs fuel and oxygen to burn.

Answer 8

The extra air provides more oxygen, it's the oxygen that makes it burn brighter.

Answer 9

I think it is because you are encouraging the oxygen part of the fire triangle