What is Fire?

No, it’s not a trick question. I’m talking about the physical make-up of fire. Remember the old G.I. Joe commercials, where “Knowing is half the battle”? The more you know about fire, the easier you’ll be able to beat it.Fires result when a flammable or combustible material is exposed to a heat or ambient temperature source above the flash point for the mix of fuel and oxidizer in the area. An oxidizer is a chemical compound that readily transfers oxygen atoms, or alternatively gains electrons through a chemical reaction. If the oxidizer is able to sustain a rapid rate of oxidation, fire will result through a chain reaction. This system is referred to as the fire tetrahedron, since all four elements (oxygen, fuel, heat, and chain reaction) must be present and in the right proportions for a fire to result. Therefore, the key to beating a fire is to remove one of these four elements. You can remove the fuel source (turning off the gas supply on a stove), the oxygen (smother the flame completely), the heat (pour water or a steady stream of air on the flame), or the chemical reaction (apply a retardant like Halon).We sense fire by the presence of flame and heat. Flame is a visual phenomenon which emits different spectra of visible and infrared light (the exact makeup depends on the specific fuel and chemical reaction). A flame gives off light with a continuous spectrum. Heat simply means that energy is transferred from one system to another through thermal contact.Just how “hot” is a typical fire? The data below, taken from Wikipedia, illustrates some common examples:Typical temperatures of fires and flames

  • Oxyhydrogen flame: 2000 C or above (3645 F)
  • Bunsen burner flame: 1,300 to 1,600 C (2,372 to 2,912 F)
  • Blowtorch flame: 1,300 C (2,370 F)
  • Candle flame: 1,000 C (1,830 F)
  • Smoldering cigarette:
    • Temperature without drawing: side of the lit portion; 400 C (752 F); middle of the lit portion: 585 C (1,085 F)
    • Temperature during drawing: middle of the lit portion: 700 C (1,292 F)
    • Always hotter in the middle.

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