There have been many questions as to how the ammonium nitrate at the West, TX fertilizer distributor could have blown up. Investigators have still not stated with 100% certainty that the explosion involved AN, but it is my belief they are just crossing all their “t’s” and dotting all their “i’s” before stating this. Unless the facility had some other energetic materials on site that they failed to report, this explosion was caused by AN exposure to the fire conditions at the facility. This posting is to try and explain the conditions in which AN fertilizer can become explosive as it decomposes. One theory the investigation team has to be looking at is what else was stored in that building that could have been INCOMPATIBLE with the AN storage. It is a known fact that the energy necessary to initiate thermal decomposition of AN decreases when the AN is sensitized. There are several conditions that can sensitize AN and increase the hazards of thermal decomposition, deflagration and detonation. They are: