Why was the AZF fertilizer plant explosion so severe?

• A. The explosion at the nearby military facility triggered much larger explosions at that facility which then caused fires at the AZF facility
• B. A terrorist bomb was planted
• C. The AZF facility was unknowingly constructed on top of an unexploded World War II era bomb
• D. A large quantity of material that can energetically decompose (ammonium nitrate) was stored in one location at the process facility

Answer: (D)

The main factor is the massive energy potential of ammonium nitrate when stored in a large, confined quantity. Ammonium nitrate can decompose exothermically and rapidly release gases; when a lot of it is kept in one place, any initiating heat or ignition can trigger a runaway reaction that produces extremely high pressures in a short time. The confinement from having hundreds of tons in a single location means that the resulting gas and pressure wave can unfold into a massive explosion, rather than a small, contained event. This combination of a potent energetic material and large, centralized storage is what makes the AZF disaster so severe. Other scenarios don’t capture why the blast was so devastating—the presence of a large quantity of a material that can energetically decompose stored together is the critical hazard.