Ammonium nitrate fuel oil

ANFO ( AN-foh) (or AN/FO, for ammonium nitrate/fuel oil) is a widely used bulk industrial high explosive. It consists of 94% porous prilled ammonium nitrate (NH4NO3) (AN), which acts as the oxidizing agent and absorbent for the fuel, and 6% number 2 fuel oil (FO). The use of ANFO originated in the 1950s. It has found wide use in coal mining, quarrying, metal ore mining, and civil construction in applications where its low cost and ease of use may outweigh the benefits of other explosives, such as water resistance, oxygen balance, higher detonation velocity, or performance in small-diameter columns. The mining industry accounts for an estimated 90% of the more than 2.5 thousand tonnes (5.5 million pounds) of explosives used annually in the United States. ANFO is also widely used in avalanche hazard mitigation.