ANFO
explosive
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.
Chemistry
The chemistry of ANFO detonation is the reaction of ammonium nitrate with a long-chain alkane hydrocarbon (CnH2n+2) to form nitrogen, carbon dioxide, and steam. In an ideal stoichiometrically balanced reaction, ANFO is composed of about 94.5% AN and 5.5% FO by weight. In practice, a slight excess of fuel oil is added, as underdosing results in reduced performance while overdosing merely results in more post-blast fumes.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Aug 12, 2026. The linked authority identifier is Q295697. The Library of Congress control number is sh85004550. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “ANFO” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.