Ammonium nitrate can be explosive, if kept in the right environment. However, Ammonium Nitrate is commonly found in fertilisers, but this has been diluted into a state which can not be used as explosive. It will take some advanced knowledge in chemistry to get the Ammonium Nitrate in fertiliser to be explosive again!
As long as the AN is kept separate from oxidizing chemicals it is very stable. AN will not explode unless confined and allowed to build pressure with an oxidiser. When involved in a fire, flooding amounts of water to cool and breakup the molten mass is required. As in the Texas City exxplosion the AN fire was in an enclosed vessel and the increase in pressure made the AN explosive.
When ammonium nitrate decomposes it releases a huge amount of gases.including oxygen.nitrogen.and water vapor.when fuel is mixed with this substance it acts like a generator it breaks down and releases these gases the cycle keeps repeating that can lead to a powerful explosion.
MMONIUM NITRATE, a salt of ammonia and nitric acid, is a colourless, crystalline substance melting at 169 C. It is highly soluble in water and soluble in alcohol and liquid ammonia. Heating may cause violent combustion or explosion. Heating of the water solution or burning decomposes the salt to toxic fumes (nitrous oxide). Ammonium Nitrate reacts with combustible and reducing materials as it is a strong oxidant. It is prepared commercially by reaction of nitric acid and ammonia. It is widely used in fertilizers and explosives. The commercial grade contains about 34 percent nitrogen, all of which is in forms utilizable by plants; it is the most common nitrogenous component of artificial fertilizers. Ammonium nitrate also is employed to modify the detonation rate of other explosives, such as nitroglycerin in the so-called ammonia dynamites, or as an oxidizing agent in the ammonals. Ammonium nitrate is also used in the treatment of titanium ores and in solid-fuel rocket propellants, in pyrotechnics.
