The catastrophic explosion at Beirut port that has so far killed at least 100 was caused by over 2,700 tonnes of ammonium nitrate kept in storage for over six years.
The nitrogen rich compound is also the main component of the explosive composition known as ANFO, ammonium nitrate fuel oil.
In its pure form, ammonium nitrate (NH4NO3) is a white, crystalline chemical which is soluble in water. It is the main ingredient in the manufacture of commercial explosives used in mining and construction.
Pure ammonium nitrate is not an explosive on its own. It is classified as an oxidiser under the United Nations classification of dangerous goods.
If mixed with ingredients like fuel or some other contaminants, or because of some other external factors, it can be very explosive.
However, for combinations to explode, triggers like detonators are required. Many Improvised Explosive Devices (IEDs) used by terrorists around the world have ANFO as the main explosive, triggered by primary explosives like RDX or TNT.
Large quantities of stored ammonium nitrate are regarded as a major fire hazard, with multiple reported cases across the world. The explosion of large storage can happen primarily in two ways.
One is by some type detonation or initiation because the storage comes in contact with explosive mixture. Second, the blast can result due to a fire which starts in the ammonium nitrate store because of the heat generated due to the oxidation process at a large scale. The second one seems to be the primary likely cause of the incident at Beirut port.
Because it is used as an ingredient for the production of industrial explosives, anaesthetic gases, fertilizers, cold packs, and has a strong possibility of misuse, ammonium nitrate is highly regulated in India, at least in letter.
The manufacture, conversion, bagging, import, export, transport, possession for sale or use of ammonium nitrate is covered under The Ammonium Nitrate Rules, 2012. The rules also make storage of ammonium nitrate in large quantities in populated areas illegal in India.
For the manufacture of ammonium nitrate, an Industrial licence is required under the Industrial Development and Regulation Act, 1951.
A license under the Ammonium Nitrate Rules, 2012 is also required for any activity related to ammonium nitrate.