Why do terrorists use ammonium nitrate often?

Recently, the nation witnessed two major blasts: the first at the Red Fort complex in Delhi on November 10, and the second at the Nowgam police station in Srinagar on the night of November 14. However, there was no car bomb or terrorist attack the second time; a large amount of explosives recovered by the investigating agency was stored in the Nowgam police station, which exploded during the examination. Experts initially concluded that the explosives behind the two incidents were primarily made from ammonium nitrate, combined with fuel oil and detonators. The possibility of other powerful explosives such as PETN, SEMTEX, and RDX was feared, but it was later revealed that their quantity was small. Blast effect It is a white crystalline powder substance, which is commonly used widely as a nitrogen-rich fertilizer to increase crop yields. The country has just witnessed how dangerous the use of this seemingly harmless chemical can be. A powerful shock wave is generated during the explosion, which causes the surrounding area to shake and the explosion to spread. Thats why it is widely used in the mining and construction industries. This chemical, comprised of ammonium (NH4+) and nitrate (NO3-) ions, is a powerful oxidizer. Simply said, it provides enough oxygen for the reaction; nevertheless, other ingredients are necessary to initiate ignition! In chemistry, ammonium nitrate is stable and safer than other explosives when kept under controlled conditions; however, when exposed to intense heat or stirring, the gas released from it will ignite an explosion if there is a liquid organic compound or a readily available incendiary substance such as a detonator. Nitrous oxide (N2O) and water vapor (H2O) are initially produced from ammonium nitrate at high temperatures (around 300C). NH4NO3N2O + 2H2O At higher temperatures, they break down to form nitrogen (N2), oxygen (O2), and water (H2O). 2NH4NO32N2+O2+4H2O Explosive reactions can also make other gases, such as ammonia (NH3), nitric oxide (NO), and nitrogen dioxide (NO2). NO2 is the one that makes the reddish-brown clouds that we observe when explosions occur. When thermal oxidation events happen at very high temperatures and pressures, they make these gases. NH4NO2 is ideal for creating improvised explosive devices (IEDs) since it looks safe and stable yet has a lot of hidden destructive power. Ease of access It is readily accessible in the market. In an agricultural nation such as India, there is significant demand, resulting in ample supply. It can be stored with ease. Other military-grade explosives, including RDX, do not face similar restrictions on ammonium nitrate for the general public. The terrorists exploited this scenario. Furthermore, it exhibits greater stability compared to first-line explosives and can be transported using regular cars, enabling attackers to accumulate substantial quantities with minimal effort. In recent times, the repeated use of ammonium nitrate has become a cause of serious concern for the security of the country. The Government of India, in 2012, enacted the Explosives Act and the Ammonium Nitrate Rules, which lay down a set of rules for its manufacture and marketing, such as compulsory licensing; not to be stored in crowded places; to be stored away from the locality with high walls; to have adequate fire extinguishers; import and export activities to be limited to certain ports; not to be sold in the open; to be sold only in packet form, etc. Not only is it necessary to create laws, but also to put them into action. The dual use of NHNO often hinders its fruitful application. To combat this ongoing threat, it is essential to use modern technology, raise public awareness, and maintain strict surveillance from the administrative place. Shamim Haque Mondal Physics Division, State Forensic Science Laboratory, Kolkata