From Wiki....
“Explosive velocity, also known as detonation velocity or velocity of detonation (VoD), is the velocity at which the shock wave front travels through a detonated explosive. The data listed for a specific substance is usually a rough prediction based upon gas behavior theory[citation needed] (see Chapman-Jouguet condition), as in practice it is difficult to measure[citation needed]. Explosive velocities are always faster than the local speed of sound in the material”
Fire alone does not provide the explosive velocity to explode ammonium nitrate. I think fuel oil is added to increase the explosiveness.
It, supposedly, was located next to a fireworks factory.
The video is pretty crazy to watch.
You see the pressure wave, then a couple seconds later hear the boom.
We used to use ammonium nitrate for blasting on the farm. It comes in 2 forms, coated and uncoated. The coating was developed to make the substance more stable, and we mixed diesel fuel with the ammonium nitrate to break down the coating. It didn’t actually improve the function of the ammonium nitrate. What I remember most is even with a bread bag of the fertilizer it took a full stick of dynamite to initiate the larger explosive. Something about this story doesn’t add up.