Fire triangle: Encyclopedia II - Fire triangle - Fire tetrahedron

Fire triangle - Fire tetrahedron

The fire triangle is a useful teaching tool, but fails to identify the fourth essential element of fire: the sustaining chemical reaction. This has led to development of the fire tetrahedron: a triangular pyramid having four sides (including the bottom). In most fires it simply doesn’t matter which element gets removed; the fire fails to ignite, or it goes out. However, there are certain chemical fires where knowing only the “fire triangle” is not good enough.

Combustion is the chemical reaction that feeds a fire more heat and allows it to continue. With most types of fires, the old fire triangle model works well enough, but when the fire involves burning metals (lithium, magnesium, etc.), it becomes useful to consider the chemistry of combustion. Putting water on such a fire could result in the fire getting hotter (or even exploding) because such metals can react with water in an exothermic reaction to produce flammable hydrogen gas. Therefore, other specialized chemicals must typically be used to break the chain reaction of metallic combustion and stop the fire.

Adapted from the Wikipedia article "Fire tetrahedron", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki