Chemistry:Ammonium nitrate disasters

When heated, ammonium nitrate decomposes non-explosively into gases including oxygen; however, it can be induced to decompose explosively by detonation. Large stockpiles of the material can be a major fire risk due to their supporting oxidation, and may also detonate, as happened in the Texas City disaster of 1947, which led to major changes in the regulations for storage and handling. There are two major classes of incidents resulting in explosions:

• In the first case, the explosion happens by the mechanism of shock to detonation transition. The initiation happens by an explosive charge going off in the mass, by the detonation of a shell thrown into the mass, or by detonation of an explosive mixture in contact with the mass. The examples are Kriewald, Morgan, Oppau, Tessenderlo, and Traskwood.
• In the second case, the explosion results from a fire that spreads into the ammonium nitrate (AN) itself (Texas City, Brest, Tianjin), or to a mixture of an ammonium nitrate with a combustible material during the fire. The fire must be confined at least to a degree for successful transition from a fire to an explosion (a phenomenon known as "deflagration to detonation transition", or DDT). Pure, compact AN is stable and very difficult to initiate. However, there are numerous cases when even impure AN did not explode in a fire.

Ammonium nitrate decomposes in temperatures above 210 °C (410 °F). Pure AN is stable and will stop decomposing once the heat source is removed, but when catalysts are present, the reaction can become self-sustaining (known as self-sustaining decomposition, or SSD). This is a well-known hazard with some types of NPK fertilizers and is responsible for the loss of several cargo ships.

Timeline of major disasters

Country	City/Location	Date	Deaths	Notes
United Kingdom	Faversham, Kent	April 2, 1916	115	The Great Explosion: On April 2, 1916, a factory in Uplees, Faversham, exploded after a fire spread to a store of 25 tons of TNT and 700 tons of ammonium nitrate. The blast at the Explosives Loading Company killed 115 people and shattered windows in Southend-on-Sea across the Thames Estuary while the tremor was felt in Norwich.
United States	Morgan, New Jersey (now Sayreville)	October 4, 1918	~100	T. A. Gillespie Company Shell Loading Plant explosion: On October 4, 1918, an explosion at the Morgan Depot occurred leading to many artillery shells being launched into the air, some of which landed on a neighbouring warehouse where 4000 tonnes of ammonium nitrate were stored in barrels. One of the shells caused a large explosion, but the majority of the ammonium nitrate did not detonate.
Germany	Kriewald	July 26, 1921	19	On July 26, 1921, in this railway town (now in Poland) workers tried to dislodge 30 tonnes of ammonium nitrate that had aggregated (solidified into one mass) in two wagons. When mining explosives were used on this solid mass the wagons exploded and killed nineteen people.
Germany	Oppau	September 21, 1921	561	Explosion at BASF plant Oppau: Another attempt at disaggregation of a fertilizer mix with industrial explosives caused the death of 561 people and left more than 2000 injured. The fertilizer was a 50:50 mixture of ammonium nitrate and ammonium sulfate and the factory had used this method of disaggregation over 20,000 times without incident. It is thought that, on this occasion, poor mixing had led to certain parts of the mass containing more ammonium nitrate than others. Only 450 tonnes exploded, out of 4500 tonnes of fertilizer stored in the warehouse.
United States	Nixon, New Jersey (now Edison Township)	March 1, 1924	20	1924 Nixon Nitration Works disaster: On March 1, 1924, a fire and several large explosions destroyed a warehouse containing ammonium nitrate at the Nixon Nitration Works. The explosiveness of the product was perhaps enhanced, as it had been prepared using nitric acid that had previously been used for the production of TNT.
United States	Muscle Shoals, Alabama	1925	0	On April 4, 1925, and May 3, 1925, two carloads, each containing 220 barrels of ammonium nitrate, were dispatched from Muscle Shoals, Alabama, and caught fire in transportation. The barrels had been stored in a warehouse with varying humidity for 6 years, so it is believed that they were ignited by friction with their nitrate-impregnated manila paper lining. Other shipments were reportedly more successful.
France	Miramas	August 5, 1940	0	240 tonnes of ammonium nitrate in sacks exploded after being hit by a shell from a nearby fire in a munitions train.
Belgium	Tessenderlo	April 29, 1942	189	Another attempt to disaggregate a pile of 150 tonnes of ammonium nitrate with industrial explosives ended tragically on April 29, 1942: 189 people were killed, 900 wounded.
United States	Texas City	April 16, 1947	581	Texas City disaster: The cargo ship Grandcamp was being loaded on April 16, 1947, when a fire was detected in the hold: at this point, 2300 tons of ammonium nitrate in sacks were already aboard. The captain responded by closing the hold and pumping in pressurised steam. One hour later, the ship exploded, killing several hundred people and setting fire to another vessel, the High Flyer, which was moored 250 metres away and which contained 1050 tonnes of sulfur and 960 tons of ammonium nitrate. The Grandcamp explosion also created a powerful earthshock that broke windows as far as 40 miles away and knocked two small planes flying at 1,500 feet (460 m) out of the sky. The High Flyer exploded the next day, after having burned for sixteen hours. 500 tonnes of ammonium nitrate on the quayside also burned, but without exploding, probably because it was less tightly packed. All but one member of the Texas City fire department died.
France	Brest	July 28, 1947	29	The Norwegian cargo ship Ocean Liberty was loaded with 3300 tonnes of ammonium nitrate and various flammable products when it caught fire at 12:30 July 28, 1947. The captain ordered the hold to be sealed and pressurised steam was pumped in. As this did not stop the fire, the vessel was towed out of the harbour at 14:00, and exploded at 17:00. The explosion caused 29 deaths and serious damage to the port of Brest.
-	Red Sea	1953	0	A fire was detected on the cargo ship Tirrenia on January 23, 1953, while it was carrying 4000 tonnes of ammonium nitrate. Attempts to extinguish the fire with steam were unsuccessful, and the ship was abandoned before it exploded later in the night.
United States	Roseburg, Oregon	August 7, 1959	14	The Roseburg Blast: A truck carrying dynamite and ammonium nitrate caught fire early in the morning of August 7, 1959. When it exploded it killed 14 people and injured 125 more. Several blocks of downtown Roseburg were destroyed. The accident is locally referred to as "The Blast".
United States	Traskwood, Arkansas	December 17, 1960	0	On December 17, 1960, a 96 freight car train suffered partial derailment, in which the last 23 cars were derailed. The derailed cars included: four fuel oil tank cars, two tank cars of gasoline, three tank cars of petroleum oil, four cars of lube oil drums, three cars of liquid fertilizer, one car of fuming nitric acid and two cars of fertilizer grade ammonium nitrate. In this particular accident, neither car of ammonium nitrate exploded. However, the nitric acid reacted with the fuel oil, essentially creating ANFO to feed the conflagration, resulting in the spread of the ammonium nitrate material around the incident site.
Australia	Taroom, Queensland	August 30, 1972	3	A truck carrying ammonium nitrate experienced an electrical fault and caught fire north of Taroom. After the driver stopped and parked the burning truck, two brothers from a nearby cattle property who saw the fire rode up on motorbikes to assist. The three men were killed when the truck exploded. The explosion burnt out more than 2000 acres of surrounding bushland, and left a deep crater where the truck had been parked. A memorial to the three men was unveiled at the accident site in 2013.
United States	Kansas City, Missouri	November 29, 1988	6	On November 29, 1988, at 4:07 AM two trailers containing approximately 50,000 lb (23,000 kg) of the explosive ANFO (ammonium nitrate with fuel oil) exploded at a construction site located near the 87th street exit of Highway 71 in Kansas City, Missouri. The explosives were to be used in the blasting of rock while constructing Highway 71. The result of the explosions were the deaths of six firemen from the Kansas City Fire Department's Pumper Companies 30 and 41. Both companies were dispatched after 911 calls indicated that a pickup truck located near the trailers had been set on fire. The responding companies were warned that there were explosives on-site; however, they were unaware that the trailers were essentially magazines filled with explosives. At 4:07 AM one of the "magazines" caught fire and a catastrophic explosion occurred, killing all six firemen instantly — only sparing remains were found. A second blast occurred 40 minutes later, although all fire crews had been pulled back at this time. The blasts created two craters, each approximately 100 feet (30 m) wide and 8 feet (2.4 m) deep. The explosions also shattered windows within a 10-mile (16 km) area and could be heard 40 miles (64 km) away. It was later determined that the explosions were acts of arson, set by individuals embroiled in a labor dispute with the construction company contracted to build the highway.
Papua New Guinea	Porgera Gold Mine	August 2, 1994	11	At 9:45 am, 2 August 1994, 11 workers were killed when the sensitised AN emulsion plant they were working on exploded at the Porgera Gold Mine. The fatal explosion involved at most a few tonnes of explosive. A larger explosion of about 80 tonnes of emulsion (Ammonium Nitrate Emulsion, ANE, UN 3375) was caused by fires under storage facilities at the site at 11:02 AM. There were no fatalities in the second explosion because the site had been evacuated. A mushroom cloud was seen to rise. ANE is an emulsion of ammonium nitrate, fuel and water.
United States	Port Neal, Iowa	December 13, 1994	4	Port Neal fertilizer plant explosion: At about 6:06 AM on December 13, 1994, two explosions rocked the Port Neal, Iowa, ammonium nitrate processing plant operated by Terra Industries. Four people were killed and 18 injured. Approximately 5,700 tons of anhydrous ammonia were released and releases of ammonia continued for six days after the explosions. Groundwater under the processing plant was contaminated by chemicals released as a result of the blast. The timing of the explosion occurred prior to the start of the arrival of the 8:00 AM shift personnel, or the death toll might have been larger.
China	Xingping, Shaanxi	January 6, 1998	22	At midnight on January 6, 1998, the Xinghua Fertilizer company had a series of explosions in the plant. About 27.6 tons of ammonium nitrate liquor was in a container there. The explosion claimed 22 lives, with a further 56 wounded. The explosion was officially announced as an accident.
France	Toulouse	September 21, 2001	31	AZF: On September 21, 2001, at 10:15 AM, in the AZF (Azote de France) fertiliser factory in Toulouse, France, an explosion occurred in a warehouse where the off-specification granular AN was stored flat, separated by partitions. About 200–300 tons were said to be involved in the explosion, resulting in 31 people dead and 2,442 injured, 34 of them seriously. The blast wave shattered windows up to 3 km away, and the resulting crater was 10 m deep and 50 m wide. The exact cause remains unknown. The material damage was estimated at 2.3 billion euros. France's Environment Minister initially suggested the explosion "may have been a terrorist attack" as it occurred soon after the September 11 attacks and one worker may have had militant views.
Spain	Cartagena, Murcia	January 2003	0	The fertilizer storage facility of Fertiberia held a self-sustained decomposition (SSD) fire in January 2003. The fire was controlled after most of the material was removed by mechanical means.
France	Saint-Romain-en-Jarez	October 2, 2003	0	A fire broke out in Saint-Romain-en-Jarez (Loire) in a barn, which at the time of the accident contained a gasoline-powered forklift, a battery charger, two 13-kg gas bottles, miscellaneous farm machinery, 500 kg of quicklime, 500 wooden crates, 6,000 to 7,000 plastic crates,and between 3 and 5 tonnes of ammonium nitrate packaged in big-bags. Bales of hay and straw were being stored on the mezzaanine and ≈500 kg apples kept in the cold storage rooms. The fire started around 3 PM, and fire-fighters were notified of the blaze at 4:02 PM. They arrived on the scene at 4:23 and started to extinguish the fire. At 5:12 PM the explosion occurred. Twenty six people were injured from the blast, most of them fire-fighters.
Spain	Barracas	March 9, 2004	2	A truck carrying 25 tonnes of ammonium nitrate fertilizer exploded half an hour after a traffic accident on March 9, 2004, killing two people and injuring five others. The explosion, which could be heard at a distance of several kilometers caused a crater five metres deep.
Romania	Mihăileşti, Buzău	May 24, 2004	18	Mihăileşti explosion: A truck carrying 20 tonnes of ammonium nitrate tipped over on the European road E85 near Mihăileşti at 4:57 AM on May 24, 2004. Shortly afterwards, a fire started in the cabin. Two reporters got to the site of the accident and started filming while firemen were trying to stop the fire. Around 5:50 AM the truck exploded, killing 18 and wounding 13 people. A crater 6.5 meters deep and 42 meters in diameter was formed by the explosion.
North Korea	Ryongchŏn	April 22, 2004	162	Ryongchon disaster: A freight train carrying ammonium nitrate exploded in this important railway town near the China border on April 22, 2004, killing 162 people and injuring over 3,000 others. The train station was destroyed, as were most buildings within 500 metres, and nearly 8,000 homes were destroyed or damaged. Two craters of about ten metres in depth were seen at the site of the explosion. The authorities blamed "human error" for the explosion, although rumours persist that it was in fact an attempt to assassinate the North Korean leader Kim Jong-Il, who was due to be passing through the station at the time.
Spain	Estaca de Bares	2007	0	The NPK fertilizer cargo of the ship Ostedijk sustained a self-sustained decomposition (SSD) fire for 11 days. The fire plume reached 10 m in diameter and several hundred meters in length. Special water spears were inserted inside the cargo to extinguish the fire.
Mexico	Monclova, Coahuila	September 10, 2007	40	On September 10, 2007, near Monclova, Coahuila, México, a pickup truck lost control and crashed into a trailer loaded with 22 tons of ammonium nitrate and fuel oil explosives (ANFO) leaving three occupants in the pick-up truck dead in the crash. A fire then started in the trailer's cabin and approximately 40 minutes after that, a huge explosion occurred, resulting in 37 deaths and around 150 more people injured. A crater 30 ft (9.1 m) wide and 6 ft (1.8 m) deep was created due to the explosion.
United States	Bryan, Texas	July 30, 2009	0	A plant in Bryan, Texas (El Dorado Chemical Company), which processes ammonium nitrate into fertilizer, caught fire at about 11:40 AM on July 30, 2009. Over 80,000 residents in the Bryan/College Station area were asked to evacuate south of town due to the toxic fumes this fire generated. Texas A&M University provided shelter at Reed Arena, a local venue on campus. Only minor injuries were reported.
United States	West, Texas	April 17, 2013	15	West Fertilizer Company explosion: A fertilizer company in West, Texas, caught fire. Around 20 minutes later, ammonium nitrate stored there exploded, leveling roughly 80 homes and a middle school. 133 residents of a nearby nursing home were trapped in the ruins. In all, 15 were killed, and about 200 injured. There were reports that the facility had stored more ammonium nitrate than it was allowed to, without regulation by the Department of Homeland Security.
Australia	Wyandra, Queensland	September 6, 2014	0	A truck carrying 56 tonnes rolled on a rural road, exploding shortly after the driver was rescued. The explosion was heard 30 km away with debris being thrown 2 km, it totally destroyed a highway bridge. The driver and 6 firemen were injured.
China	Port of Tianjin	August 12, 2015	173	2015 Tianjin explosions: Nitrocellulose stored at a hazardous goods warehouse spontaneously combusted after becoming overly hot and dry, resulting in a fire that 40 minutes later triggered the detonation of about 800 tonnes of ammonium nitrate stored nearby. 110 emergency personnel and 55 residents and employees were killed, while 8 are missing. 798 people were injured. There was extensive damage to structures and goods at the port, damage to surrounding apartment blocks, and severe damage to a railway station.

See also

• List of the largest artificial non-nuclear explosions, many of which involved ammonium nitrate