Ammonium Nitrate Explosions: Common Factors in Major Disasters

Damage in the aftermath of devastating explosion in Beirut, Lebanon
Damage in the aftermath of devastating explosion in Beirut, Lebanon. Voice of America photo
Damage in the aftermath of devastating explosion in Beirut, Lebanon
Damage in the aftermath of devastating explosion in Beirut, Lebanon. Voice of America photo

By George H. Potter

Ammonium nitrate (AN) is the basic component of most fertilizers as well as various types of munitions. The manufacture, manipulation, transport, storage and inadequate use of this substance can contribute to a detonation that provokes violent explosions which in turn results in frequent disasters with multiple fatalities and extremely extensive material damage. One example of this is the recent catastrophe in Beirut, Lebanon, which killed at least 100 people and injured thousands.

The following is a brief look at what happens when AN is exposed to fire or a source of ignition. There is also a comparison of several of the most disastrous incidents involving AN, during fabrication, storage, and transport, and some insight into what can or should be done to prevent or mitigate possible accidents. It is curious that it seems to be about 25 or so years between some of these important tragedies.


From the Fire Engineering Vault: Texas City Explosion

The Texas City Disaster

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When AN is heated, it decomposes into an essentially non-explosive situation with the release of gases of oxygen, nitrogen, and water vapor. However, AN can be induced to decompose explosively into nitrous oxide and water vapor. Large stockpiles of the material can become a major fire risk due to their supporting oxidation and may also detonate, as happened in the Texas City disaster in 1947, which led to major changes in the regulations for storage and handling in the United States. The Beirut disaster in August was nearly a photocopy of the Texas City incident.

There are two major classes of incidents that generally result in explosions of AN:

  1. Explosive charge into the mass of AN or in direct contact with the mass of AN.
  2. Fire spread into the AN mass or to a mixture of AN with a combustible material during a fire.

Pure, compact AN is stable and it is difficult to initiate combuston. AN decomposes in temperatures above 410ºF. Pure AN will cease decomposition once the heat source is removed. However, if catalysts are present, the reaction can become self-sustaining, a well-known hazard with some types of NPK fertilizers. This is a frequent occurrence in cargo ships during transport.

Major Loss-of-Life Incidents

Since the beginning of the 20th century, there have been 35 major incidents involving ammonium nitrate. Of these, 10 resulted in no fatalities; in 18 cases, there were between one and up to nearly 100 victims; and there were seven in which more than 100 persons lost their lives. In nearly all of these incidents, material damage was extensive to extremely devastating, resulting in losses of hundreds of millions of dollars. The majority of these incidents occurred during the manufacture or storage of AN as the primary substance present or as fertilizers.

Year: 1916     

Country: England 

Number of deaths: 115

Tons of AN involved: 700

Observations: Fire spread to a storage of 25 tons of AN.

Year: 1921

Country: Germany 

Number of deaths: 561, with 2,000 injured

Tons of AN involved: 450, with total storage of 4,500 tons

Observations: Fertilizer plant using industrial explosives in manufacturing process. Inadequate mixture was the probable cause of the explosion involving  450 tons (10 percent) of the total AN present in the plant.

Year: 1942

Country: Belgium

Number of deaths: 189, with 800 injured

Tons of AN involved: 150

Observations: Use of explosive material in process phase.

Year: 1947

Country: USA

Number of deaths: 581, with 5,000 injured

Tons of AN involved: 2,086 + 870 in secondary ship

Observations: Fire in cargo hold of a ship with 2,300 tons of AN aboard caused the explosion. Probable cause was closing the hold and injecting pressurized steam into the hold. The explosion provoked a fire on another ship some 750 feet away, also with AN aboard (960 tons) plus 1,050 tons of sulphur. The second ship exploded the following day. The shock wave of the first explosion caused the crash of two light aircraft flying at 1,500 feet above the area, and projected one anchor more a mile from the site. All but one member of the Texas City VFD were killed in the disaster. A contributing factor was the purposely erroneous Bill of Lading done by the ship’s captain.

Year: 2004

Country: North Korea

Number of deaths: 162, with 3,000 injured

Tons of AN involved: Unknown

Observations: Freight train exploded in a railway station. “Official” blame was on human error, however, rumors persist that it was an attempt to assassinate the country’s leader, Kim Jong-Il.

Year: 2015

Country: China

Number of deaths: 173, with 800 injured

Tons of AN involved: 800

Observations: Spontaneous combustion in nitrocellulose storage caused a fire that provoked detonation of AN stored nearby. One hundred and ten of the victims were emergency response personnel.

Year: 2020

Country: Lebanon

Number of deaths: 145+, with at least 5,000 injured

Tons of AN involved: 2,750

Observations: A fire in a warehouse in the port of Beirut spread to 2,750 tons of AN in precarious conditions stored nearby. The shock wave was felt on the island of Cyprus, some 150 miles away. Damage was so severe that some 300,000 people have lost their homes. Fireworks and munitions stored adjacent to the under-supervised AN storage were involved in the initial fire. At the time of this writing, investigations are still underway, and the death toll will almost certainly rise.

The Texas City and Beirut disasters merit further analysis. Although the principal explosive materials were essentially the same, ammonium nitrate, and both incidents occurred in seaports, there are a number of differences between the two.

The Texas City fires and explosions were initially aboard cargo ships, whereas the Beirut explosions were on land, apparently in and around storage warehouses. The AN in Texas City had been produced a relatively short time before the incident and was being prepared for shipment to Europe. The initial fire was apparently confined in the cargo hold and was being attacked by the ship’s crew. As the fire was not controlled by the crew and the volunteer firefighters of the Texas City (TX) Volunteer Fire Department that had arrived at the scene, the ship’s captain ordered the fire attack to cease and that pressurized steam be injected into the cargo hold. Apparently, the steam further heated the AN, which began decomposition, releasing nitrous oxide, oxygen, and water vapor. A probable chain reaction involving the nitrous oxide evolved into the violent explosion that literally blew the ship apart, killing the crew, 27 members of the Texas City fire department, and four from a nearby volunteer fire department, and hundreds of curious bystanders who had gathered around the scene. The violence of the explosion destroyed numerous facilities in the immediate area, including various chemical, petrochemical, and other industrial plants. Two other ships were seriously affected, one of which also had several hundred tons of AN aboard and caught fire and exploded the following day,. Damage to other buildings in the town was also extremely severe, as the majority of small and medium sized buildings, offices, commercial stores, and homes were built of wood. The overall scene of several square miles resembled Hiroshima.

In 2005, a multiple fires and explosions in a refinery in Texas City took 15 lives and injured 180 more, as well as provoking billions of dollars in material and property damages. Today, Texas City has a population of some 45,000 and a full-time professional fire department with a roster of 81, including the city’s fire marshall and staff, administration personnel, and 69 firefighters.

The Beirut disaster involved some 2,750 tons of AN that had been confiscated from a cargo ship some six years ago enrooted to another country, the vessel had stopped in Beirut with the intention of taking on additional cargo. The AN had been removed from the ship and put into a warehouse with no special security nor safety considerations. Over the years, some of the AN had either decomposed or degenerated and was ripe for ignition. A fire broke out in an adjacent facility where quantities of munitions and fireworks were stored together. That fire spread rapidly although the Beirut fire brigade had dispatched vehicles and crews. These materials exploded, provoking the rapid projection of burning material to the AN. The resulting explosion destroyed numerous buildings in area, including the country’s principal grain silos. Ten members of the city’s fire brigade were killed as well as dozens of port area employees and a number of residents in the immediate area. During the following days, several members of the port authority including the manager were placed under house arrest. Citizens, outraged at having learned about the absolute lack of safety and security measures in the AN storage site, participated in at times violent protests against the municipal and national governments. Several key political figures have also resigned in protest. The nation’s military has been assigned to control security and safety in the area. One factor of this particular incident is paramount—the AN had been allowed to decompose, making it an invitation to disaster.

As is well known, the former Mediterranean “paradise” has been involved in several wartime situations with the Iranian-backed Hezbollah, Syrian forces, and Israel during the last several decades. Soon after the explosions, some people asserted that bombs had initiated the explosions, but subsequent investigations proved these claims to be untrue.

Lessons Learned

A report published in the Loss Prevention Bulletin 142, April, 2015. “Lessons Learned from Major Accidents Involving Fertilizers,” written by Zsuzsanne Gyernes and Maureen Heraty Wood of the Institute for the Protection and Security of the Citizen, European Commission Joint Research Centre, Italy, looked at various issues involving AN emergencies and recommendations.

The most frequent problems involving fires and explosions in ammonium nitrate are poor safety management, including inadequate fire prevention and the lack of proper fire protection and control systems. The authors also cited the lack of knowledge of the inherent hazards associated with handling and storage of AN as well as the lack of knowledge about the possible decomposition of fertilizers.

Some recommendations:

  • Establish adequate safety procedures, most importantly in hazard awareness and  training.
  • Responsible authorities should address land-use planning around AN installations.
  • Pre-emergency incident planning by local emergency response entities should be  prepared, implemented and practiced, coupled with frequent drills and live-fire response training exercises.

It is quite likely that numerous “minor” incidents including deflagrations and fires have occurred during this time frame in many parts of the world, more often than not having been considered by local emergency and political authorities as being of little or no importance. Nonetheless, much can and should be learned from these “minor” incidents that could well be useful when the “big one” happens.

George H. Potter is a practicing fire protection specialist who has lived in Spain for the past four decades. He served as an Anne Arundel County (MD) volunteer firefighter with the Riva Volunteer Fire Department and the Independent Hose Company in Annapolis and as an ambulance driver with the Wheaton (MD) Rescue Squad. He served six years in the United States Air Force as a firefighter, an apparatus driver/operator, and a crew chief. He has been involved in fire protection system installation, mobile fire apparatus design, and construction and fire safety training. He is a Spain-certified fire service instructor and a hazmat specialist, and is a member of the Board of Governors of the Spanish Firefighters’ Association (ASELF).


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