ANFO

ANFO, also written as AN/FO (an acronym for ammonium nitrate/fuel oil; AN-foh) 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) (road diesel). The use of ANFO originated in the 1950s. It is highly insensitive as an explosive, requiring a quantity of secondary explosive, known as a primer or a booster (larger than a standard blasting cap), in order to be detonated. 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 5.5 million pounds (2.5 thousand tonnes) of explosives used annually in the United States. ANFO is also widely used in avalanche hazard mitigation. ANFO mixed with nitromethane as the fuel is known as ANNM.