In an explosion in the port of the Lebanese capital Beirut, dozens died on Tuesday, the 4th of August 2020, and thousands more were injured. According to local security services, more than 2,700 tons of ammonium nitrate had been stored in the exploded warehouse since 2014.

What kind of fabric is this and what is it used for?

Ammonium nitrate is a very water-soluble salt of nitric acid and ammonia. Basically it is mainly used as fertilizer in agriculture. The agent extracts moisture from the soil, so that a lot of nitrogen is released into the soil. This promotes plant growth.

It is also an essential component of ANFO, a mixture of ammonium nitrate and fuel oil, which is widely used as an explosive in mining and has largely displaced dynamite in that sector.

In addition, the substance is regularly used by terrorists when making bombs, because it is relatively easily available due to agricultural use.

Ammonium nitrate itself is not very flammable. Stored ammonium nitrate, such as in Beirut, does not explode by itself. A series of circumstances is needed to lead to such an explosion. This always requires a fuel or external catalytic converter. The substance by itself is not very flammable.

Ammonium nitrate is a so-called oxidizing agent: it enhances combustion and ensures that other substances can ignite more easily.

That is why strict regulations apply to the storage of ammonium nitrate in most countries. For safety reasons, it should be kept away from fuels and heat sources.

In the past, ammonium nitrate has been at the root of large – mainly industrial – explosions more often.

Ammonium nitrate was implicated in an explosion at a chemical plant in the French city of Toulouse in 2001 that killed 31 people and was ruled accidental. The material was also used in a blast at a fertiliser plant in the US state of Texas in 2013, killing 15, that the authorities judged to be a deliberate attack.

In 1947, 581 people were killed in an industrial disaster in Texas City in 1947. A fire took hold as a consignment of ammonium nitrate fertiliser was being unloaded at the city’s port. The resulting explosion was reportedly heard over 200 kilometres away and set off a chain reaction that destroyed ships, small planes flying overhead, and caused a tidal wave.

Terrorist groups, such as the Taliban, have used the drug to make (improvised) bombs. Ammonium nitrate was also a part of the bomb in the attack in the American city of Oklahoma City in 1995.

Smaller explosions preceded mega-explosion. Judging by video footage, the mega-explosion in Beirut probably preceded smaller explosions, according to experts.

Pressure was building up at the bottom of the fire. At one point it was enough to trigger a mass explosion. And when that does, 2,700 tons of ammonium nitrate is really enormous.