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Deflagration and Detonation

Deflagration and Detonation:


It is a technical term describing subsonic combustion that usually propagates through thermal conductivity hot burning material heats the next late of cold material and ignites it. Most fires in daily life from flames to explosion are technically Deflagration. In free-air Deflagration, there is continuous variation in Deflagration effects relative to flame velocity. When flame velocities are low, the effect of a Deflagration is the release of heat. This is also known as flash fire at flame velocities near the speed of sound, the energy released is in the form of pressure and the results resemble a detonation between these extremes.

When low speed Deflagration occurs within a closed vessel or structure, pressure effects can produce damage due to expansion of gases as a secondary effect. The heat released by the Deflagration causes the combustion gases sand excess air to try to expand thermally as well. The net results are that the volume to the vessel or structure needs either to expand/fail to accommodate the hot combustion gases or build internal pressure to contain them.


Detonation is a process of combustion in which a supersonic shock wave is propagated through a fluid due to air energy release in a reaction zone. It is the more powerful of the two general classes of combustion the other one being Deflagration. In detonation, the shock compresses the material thus increases the temperature to the point of ignition. The ignited material burns behind the shock and releases energy that supports the shock propagation.

It is slower than the sound speed in the material itself. Because detonations generate high pressure they are more destructive than Deflagration. Detonations can be produced by explosives, reactive gaseous mixtures, certain, dusts and aerosols. Fire ball is a some what spherical mass of fire such as that caused by an explosion. Fire ball is a some what spherical mass of fire such as that caused by an explosion.

Sources of Ignition:


  • Frictional.
  • Static Change.
  • Loose Electrical Connections.
  • Lightening.
  • Welding.

Flames: Match Stick lighted.

Heat of Chemical Reactions: Cutting Torch, Heat of Compression.

Exothermic Reactions: Nuclear Heat Energy.