ANFO

Ammonium nitrate prills used in ANFO at a potash mine.
25 kg (55 lb) sacks containing ANFO

ANFO (or AN/FO, for ammonium nitrate/fuel oil) is a widely used bulk industrial explosive. Its name is commonly pronounced as "an-fo".

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).[1]

ANFO has found wide use in coal mining, quarrying, metal 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. ANFO is also widely used in avalanche hazard mitigation.[2]

It accounts for an estimated 80% of the 2.7×109 kg (6×10^9 lb) of explosives used annually in North America.[3]

The press and other media have used the term ANFO loosely and imprecisely in describing improvised explosive devices (IEDs), in cases of fertilizer bombs (see Malicious use below).[4]

The use of ANFO originated in the 1950s.[5]

Chemistry

The chemistry of ANFO detonation is the reaction of ammonium nitrate with a long-chain alkane (CnH2n+2) to form nitrogen, carbon dioxide, and water. In an ideal stoichiometrically balanced reaction, ANFO is composed of about 94.3% AN and 5.7% 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.[6] When detonation conditions are optimal, the aforementioned gases are the only products. In practical use, such conditions are impossible to attain, and blasts produce moderate amounts of toxic gases such as carbon monoxide and nitrogen oxides (NOx).

The fuel component of ANFO is typically diesel, but kerosene, coal dust, racing fuel, or even molasses have been used instead. Finely powdered aluminium in the mixture will sensitise it to detonate more readily.[7]

ANFO is classified as a blasting agent, meaning that it decomposes through detonation rather than deflagration at a velocity higher than the speed of sound in the material but cannot be detonated with a No. 8 blasting cap without a sensitizer. ANFO has a moderate velocity compared to other industrial explosives, measuring 3,200 m/s in 130 mm (5 in) diameter, unconfined, at ambient temperature.

ANFO is a tertiary explosive, meaning that it cannot be set off by the small quantity of primary explosive in a typical blasting cap. A larger quantity of secondary explosive, known as a primer or a booster, must be used.[8] One or two sticks of dynamite were historically used; current practice is to use Tovex or cast boosters of pentolite (TNT/PETN or similar compositions).[9]

Other Languages
español: ANFO
فارسی: آنفو
français: ANFO
한국어: ANFO
hrvatski: ANFO
italiano: ANFO
Nederlands: ANFO
日本語: アンホ爆薬
norsk: ANFO
oʻzbekcha/ўзбекча: Dinamonlar
polski: ANFO
português: ANFO
română: ANFO
русский: АСДТ
slovenščina: ANFO
suomi: ANFO
svenska: ANFO
ไทย: แอนโฟ
Türkçe: Anfo
українська: Ігданіт