Today in Disaster History: Oppau Germany Factory Explosion:
On the morning of September 21, 1921, workers at the BASF nitrate plant in Oppau, Germany, were preparing to break up gigantic blocks of chemical fertilizer with dynamite. It was a routine procedure that had been performed tens of thousands of times without incident.
This time, however, 9 million pounds of mixed ammonium nitrate and sulphate exploded with tremendous power. The factory was blown to pieces and half of Oppau was destroyed in the blast. The explosion killed 561 workers and residents of the town. It was later revealed that the factory had recently started using a different recipe with higher concentrations of ammonium nitrate in the mix.
Although efforts were made to reduce the risk of future explosions, every decade since has been marked by explosions of ammonium nitrate somewhere in the world.