Editing ANFO (section)

== Chemistry ==

The chemistry of ANFO detonation is the reaction of ammonium nitrate with a long-chain [[alkane]] (C<sub>n</sub>H<sub>2n+2</sub>) to form [[nitrogen]], [[carbon dioxide]], and [[steam]]. In an ideal [[stoichiometric]]ally 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.<ref name="pothole" /> When detonation conditions are optimal, the 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 oxide]]s ([[NOx|NO<sub>x</sub>]]).

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.<ref>{{cite book |last=Singh |first=R. D. |title=Principles and Practices of Modern Coal Mining |year=2005 |publisher=New Age International |isbn=9788122409741 |page=532}}</ref>

=== Explosive properties ===
ANFO is highly insensitive, making it a [[tertiary explosive]] (or a "blasting agent"). Without a sensitizer, it cannot be detonated by a typical (such as No. 8) [[Detonator|blasting cap]]  with the small amount of primary explosives within. A larger quantity of secondary explosive, known as a primer or a [[explosive booster|booster]], must be used.<ref name=duPont>{{cite book |publisher=E. I. du Pont de Nemours & Company |title=Blasters' Handbook |edition=15th |year=1969 |pages=64–68 |asin=B000JM3SD0}}</ref> One or two sticks of [[dynamite]] were historically used; current practice is to use [[Tovex]] or [[cast booster]]s of [[pentolite]] (TNT/[[PETN]] or similar compositions).<ref>{{cite web |url=http://www.globalsecurity.org/military/systems/munitions/explosives-anfo.htm |title=Explosives – ANFO (Ammonium Nitrate – Fuel Oil) |publisher=GlobalSecurity.org |access-date=3 March 2013}}</ref>

ANFO is technically a [[high explosive]] in that it decomposes through [[detonation]] rather than [[deflagration]] at a velocity higher than the speed of sound in the material, but the low sensitivity means that it is not generally regulated as such. ANFO has a moderate [[velocity of detonation|velocity]] compared to other industrial explosives, measuring 3,200&nbsp;m/s in {{convert|5|in|mm| abbr=on|order=flip}} diameter, unconfined, at ambient temperature.<ref name=duPont/> It is described as a ''non-ideal high explosive'', as its explosive velocity is far from the thermodynamic ideal due to its porosity and the phase separation of its two components.<ref name=improve>{{cite journal |last1=Fabin |first1=M |last2=Jarosz |first2=T |title=Improving ANFO: Effect of Additives and Ammonium Nitrate Morphology on Detonation Parameters. |journal=Materials |date=1 October 2021 |volume=14 |issue=19 |doi=10.3390/ma14195745 |doi-access=free |pmid=34640139|pmc=8510347 }}</ref>