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The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite
Spontaneous combustion

Spontaneous combustion may refer to:* Spontaneous combustion, the self-ignition of a mass, for example, a pile of oily rags.* Spontaneous Combustion , a 2007 album by Liquid Trio Experiment...
 in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy
Activation energy

In chemistry, activation energy is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined as the energy that must be overcome in order for a chemical reaction to occur....
 needed for combustion
Combustion

Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames, appearance of light flickering....
. The temperature at which a chemical will ignite decreases as the pressure increases or oxygen concentration increases. It is usually applied to a combustible fuel mixture.

Autoignition temperatures of liquid chemicals are typically measured using a 500 mL flask placed in a temperature controlled oven in accordance with the procedure described in ASTM E659 .

time it takes for a material to reach its autoignition temperature when exposed to a heat flux
Heat flux

Heat flux or thermal flux, sometimes also referred to as heat flux density or heat flow rate intensity is a flow of energy per unit of area per unit of time....
  is given by the following equation



where k = thermal conductivity (W/(m·K)), ? = density (kg/m³), and c = specific heat capacity (J/(kg·K)) of the material of interest.






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The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite
Spontaneous combustion

Spontaneous combustion may refer to:* Spontaneous combustion, the self-ignition of a mass, for example, a pile of oily rags.* Spontaneous Combustion , a 2007 album by Liquid Trio Experiment...
 in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy
Activation energy

In chemistry, activation energy is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined as the energy that must be overcome in order for a chemical reaction to occur....
 needed for combustion
Combustion

Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames, appearance of light flickering....
. The temperature at which a chemical will ignite decreases as the pressure increases or oxygen concentration increases. It is usually applied to a combustible fuel mixture.

Autoignition temperatures of liquid chemicals are typically measured using a 500 mL flask placed in a temperature controlled oven in accordance with the procedure described in ASTM E659 .

Autoignition equation

The time it takes for a material to reach its autoignition temperature when exposed to a heat flux
Heat flux

Heat flux or thermal flux, sometimes also referred to as heat flux density or heat flow rate intensity is a flow of energy per unit of area per unit of time....
  is given by the following equation



where k = thermal conductivity (W/(m·K)), ? = density (kg/m³), and c = specific heat capacity (J/(kg·K)) of the material of interest. is the temperature, in kelvins, the material starts at (or the temperature of the bulk material), and q″ is the heat flux (W/m²) incident to the material.

Autoignition point of selected substances

Temperatures vary widely in the literature and should only be used as estimates. Factors which may cause variation include partial pressure
Partial pressure

In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....
 of oxygen, altitude, humidity, and amount of time required for ignition.

  • Triethylborane
    Triethylborane

    Triethylborane , also called triethylborine and triethylboron, is an organoborane , a near-colorless to yellowish transparent liquid with pungent diethyl ether-like odor....
    : -20°C (-4°F)
  • Silane
    Silane

    Silane is a chemical compound with chemical formula siliconhydrogen4. It is the silicon Analog of methane. At room temperature, silane is a gas, and is pyrophoric ? it undergoes spontaneous combustion in air, without the need for external ignition....
    : <21°C (70°F)
  • White phosphorus: 34°C (93°F)
  • Carbon disulfide
    Carbon disulfide

    Carbon disulfide is a colorless, volatile liquid with the chemical formula CS2. The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non-polar solvent....
    : 90°C (194°F)
  • Diethyl ether
    Diethyl ether

    Diethyl ether, also known as ether and ethoxyethane, is a clear, colorless, and highly flammable liquid with a low boiling point and a characteristic odor....
    : 170°C (338°F)
  • Diesel
    Diesel

    Diesel or diesel fuel in general is any fuel used in diesel engines. The most common is a specific fractional distillation of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid or gas to liquid diesel, are increasingly being developed and adopted....
     or Jet A-1
    Jet fuel

    Jet fuel is a type of aviation fuel designed for use in aircraft powered by Aircraft engine#Gas turbine engine configurations. It is clear to straw colored....
    : 210°C (410°F)
  • Paper
    Paper

    Paper is thin material mainly used for writing upon, printing upon or packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
    : 218°-246°C (424-474°F)
  • Gasoline
    Gasoline

    File:GasCan.jpgGasoline or petrol is a petroleum-derived liquid mixture, primarily used as fuel in internal combustion engines.It consists mostly of aliphatic hydrocarbons, enhanced with iso-octane or the aromatic hydrocarbons toluene and benzene to increase its octane rating....
     (Petrol): 246-280°C (475-536°F)
  • Magnesium
    Magnesium

    Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....
    : 473°C (883°F)
  • Butane
    Butane

    Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH3CH2CH2CH3....
    : 500°C (900°F)
  • Hydrogen
    Hydrogen

    Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
    : 571°C (1060°F)


See also

  • Pyrolysis
    Pyrolysis

    Pyrolysis is the chemical decomposition of a condensed substance by heating. The word is coined from the Greek language-derived morphemes pyro "fire" and lysys "decomposition"....
  • Flash Point
    Flash point

    The flash point of a flammability liquid is the lowest temperature at which it can form an ignitable mixture in air. At this temperature the vapour may cease to burn when the source of ignition is removed....
  • Gas burner
    Gas burner

    A gas burner is a device to generate a flame to heat up products using a gaseous fuel such as acetylene, natural gas or propane. Some burners have an air inlet to mix the fuel gas with air to make a Combustion....
     (For flame temperatures, combustion heat energy values and ignition temperatures)
  • Fahrenheit 451
    Fahrenheit 451

    Fahrenheit 451 is a dystopian speculative fiction novel authored by Ray Bradbury and first published in 1953.The novel presents a future American society in which the masses are Hedonism, and critical thought through reading is outlawed....


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