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brooksmosesAmmonium nitrate is not normally considered an explosive; it's used as fertilizer. It is also a rather strong oxidizer, and can be made into an explosive by mixing it with fuel oil or other similar fuel, which is why many countries tightly control it.
Normally, when heated, ammonium nitrate will decompose into gaseous ammonia and nitrous acid (which is the opposite of how it's usually made) [1]. This reaction absorbs heat, which limits how hot the ammonium nitrate will get and means that it is very rare for fire to cause ammonium nitrate to explode [2, p. 2-4].
However, if ammonium nitrate is heated in a sufficiently contained manner, as would happen in a combination of a fire and small explosions, or in the blast wave of a large explosion, it will decompose into nitrogen, oxygen, and water [2, p. 59]. This reaction releases about 118 MJ/mol of the ammonium nitrate [see numbers in 3], which amounts to about 1.48MJ/kg.
(For the curious, the paper I reference as citation 2 is a very thorough study of what circumstances will cause ammonium nitrate to explode, partly in relation to a traincar load of it that exploded in a fire in 1961.)
Using that number, we can estimate that the energy released by explosive decomposition of 2700 tons of ammonium nitrate is about 4TJ, or right about a standard kiloton of TNT. It would likely also produce various nitrogen oxides, notably including nitrogen dioxide, which is a characteristic red-brown color [4].
As it happens, the U.S. military once piled a half-kiloton of TNT into a big pile and blew it up, so we have a reference picture: a half-kiloton of unexploded TNT looks like this.
Normally, when heated, ammonium nitrate will decompose into gaseous ammonia and nitrous acid (which is the opposite of how it's usually made) [1]. This reaction absorbs heat, which limits how hot the ammonium nitrate will get and means that it is very rare for fire to cause ammonium nitrate to explode [2, p. 2-4].
However, if ammonium nitrate is heated in a sufficiently contained manner, as would happen in a combination of a fire and small explosions, or in the blast wave of a large explosion, it will decompose into nitrogen, oxygen, and water [2, p. 59]. This reaction releases about 118 MJ/mol of the ammonium nitrate [see numbers in 3], which amounts to about 1.48MJ/kg.
(For the curious, the paper I reference as citation 2 is a very thorough study of what circumstances will cause ammonium nitrate to explode, partly in relation to a traincar load of it that exploded in a fire in 1961.)
Using that number, we can estimate that the energy released by explosive decomposition of 2700 tons of ammonium nitrate is about 4TJ, or right about a standard kiloton of TNT. It would likely also produce various nitrogen oxides, notably including nitrogen dioxide, which is a characteristic red-brown color [4].
![[4]](https://en.wikipedia.org/wiki/Nitrogen_dioxide#/media/File:Nitrogen_dioxide_at_different_temperatures.jpg){kind=link}
As it happens, the U.S. military once piled a half-kiloton of TNT into a big pile and blew it up, so we have a reference picture: a half-kiloton of unexploded TNT looks like this.
