Oppau Explosion – 1921

Ignorance can be bliss – until disaster strikes. Before World War I the BASF (Badische Anilin- und Soda Fabrik) dye works in Oppau made – among various other chemicals – ammonium sulphate, an inorganic salt with assorted applications including widespread use as fertilizer. From 1914, ammonium nitrate was added to the factory’s repertoire as it was a vital component of explosives needed to sustain the German war effort. After the Armistice BASC continued to produce both ammonium sulphate and ammonium nitrate, mixing them to produce rich fertilizer.

Unfortunately, the combination produced a putty-like substance that sometimes set hard inside the factory’s giant storage silo. This build-up couldn’t be removed manually, so was dislodged by using small dynamite charges. Though the properties of ammonium nitrate as an oxidizing agent in manufactured explosives were well known, it was not appreciated at the time that the compound was potentially volatile in its own right. If anyone had suspicions, they were nullified by the fact that the dynamite method had been thoroughly tested and thousands of firings had taken place without incident.

That changed in a microsecond on the morning of September 21 1921. Nobody was left alive to explain what went wrong, but it is assumed that a routine blasting session set off a mixture that had a higher-than-usual concentration of ammonium nitrate. Up to 4,500 tonnes of ammonium mixture went up. The massive blast killed over 500 people instantly, injured thousands and flattened the factory. Most of Oppau’s buildings were destroyed, leaving 6,500 residents homeless. A pressure wave ripped roofs off over a 25 km (15 mi) radius and shattered windows over a wider area. The explosion was heard in Munich, 300 km (185 mi) away, ensuring that the world would no longer be in ignorance of the awesome destructive power of ammonium nitrate.

When: September 21 1921

Where: Oppau, Ludwigshafen, Rhineland-Palatinate, Germany

Death toll: Never officially confirmed, but many sources claim the figure to be 565. Despite early press reports that the Oppau death toll was over 1,000, it is now generally accepted that the figure was between 500 and 600, with around 2,500 injured.

You should know: Terrorists and freedom fighters everywhere use widely available ammonium nitrate fertilizer as the main component in the lEDs (improvised explosive devices) that range from relatively small roadside devices targeting passing vehicles to massive truck bombs used to devastate urban areas and cause extensive loss of life.