Flash Points and Fire Breathing

By Tracy V. Wilson, HowStuffWorks.com

TIME WARP VIDEO

Video

HOWSTUFFWORKS.COM

Want to learn more about feats with fire? See How Fire Breathing Works and How Firewalking Works at HowStuffWorks.com.

A dramatic plume from the mouth of a fire breather can look like something of a contradiction. There's fuel in the air (which is burning), and there's fuel in the performer's mouth (which isn't). If all goes well, the fire breather is controlling something that seems uncontrollable -- fire.

One reason boils down to technique. Fire breathers practice producing a spray of fuel that's just the right consistency and moves at just the right angle. A spray of too-big droplets won't burn well, but if the droplets are too small, the results can be hard to predict. If the angle's too high, the fuel can fall back onto the performer. Too low, and the burning vapors can rise into the fire breather's face.

Equally important is the flash point of the fire breather's fuel, which has to do with how fast the fuel evaporates. Rising temperatures excite the fuel's molecules, making them move faster. As a result, the liquid evaporates faster. In the case of flammable liquids, the process of evaporation will eventually produce an ignitable vapor when mixed with air. The temperature at which this happens is a fuel's flash point.

Think about alcohol as an example. It evaporates quickly at room temperature, which is why it feels cool on your skin. At the surprisingly low temperature of 53 degrees Fahrenheit (13 degrees Celsius), alcohol evaporates quickly enough to form a flammable mixture in air. This flash point is far too low for use in fire breathing.

Instead, fire breathers use fuels with high flash points, like kerosene and lamp oil, also known as paraffin. Even though these are fuels, they have high flash points -- higher than 100 degrees Fahrenheit (38 degrees Celsius). This reduces the risk of accidental ignition , although these fuels aren't meant to be ingested, anyway. In fact, there's even a medical condition called hydrocarbon pneumonitis, also known as fire-eater pneumonia.