Lebanese Prime Minister Hassan Diab said 2,750 metric tons of ammonium nitrate that had been stored for years in a Beirut portside warehouse had blown up, killing dozens of people and causing unprecedented damage to the Lebanese capital.
However, under normal storage conditions and without very high heat, it is difficult to ignite ammonium nitrate, Jimmie Oxley, a chemistry professor at the University of Rhode Island, told AFP.
“If you look at the video [of the Beirut explosion], you saw the black smoke, you saw the red smoke, that was an incomplete reaction,” she said.
“I am assuming that there was a small explosion that instigated the reaction of the ammonium nitrate – whether that small explosion was an accident or something on purpose I haven’t heard yet.”
That’s because ammonium nitrate is an oxidiser – it intensifies combustion and allows other substances to ignite more readily, but is not itself very combustible.
For these reasons, there are generally very strict rules about where it can be stored; for example, it must be kept away from fuels and sources of heat.
In fact, many countries in the European Union require that calcium carbonate be added to ammonium nitrate to create calcium ammonium nitrate, which is safer.