The Oppau 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. The Meuse Valley Killer Fog: On December 2, 1930, an unusual weather front trapped a layer of air under a blanket of heavy fog in Belgium's Meuse Valley over a 15-mile long stretch of farms and factories. Unbeknownst to residents, deadly fluorine gases from the factories at the northeast end of the valley were trapped in the fog. People began to notice dead birds and pets along the northern hills. The air smelled strange and burned the eyes and throats of residents. On the third day of heavy fog, people began to die. The elderly and sick succumbed first. Sixty people died and 1,000 became seriously ill. Death rates rocketed to ten times normal. On the sixth day, the fog lifted but residents of the Meuse Valley finally recognized the potential dangers of living next to heavy industry.