Yesterday's explosion in Beirut, Lebanon, has left at least 100 people dead and thousands more injured. Multiple news sources are now saying the blast, which could be heard from 150 miles away, was due to large quantities of ammonium nitrate being stored in a warehouse in the city's port.
The update has left many wondering what ammonium nitrate is and how it could have caused such a powerful explosion. NFPA addresses the hazards the material poses in NFPA 400, Hazardous Materials Code.
An oxidizer, not an explosive
Ammonium nitrate is commonly used as in fertilizer. Although news sources like the New York Times and CNN have described it as a "highly explosive chemical," ammonium nitrate isn't technically classified as an explosive, or even flammable, material. Instead, it's what's known as an oxidizer—an oxygen-rich compound that can accelerate fires or explosions, but one that needs another element to destabilize it in the first place for such a reaction to begin.
In the case of Beirut, the reported 2,750 tons of ammonium nitrate being stored in the warehouse could have become destabilized from heat or flames from the fire that was burning before the massive blast, Guy Colonna, an engineering director at NFPA, explains in a recent video about the incident. "Ammonium nitrate does not burn, it's not flammable, it's not combustible," Colonna says. "It doesn't become explosive ... until it becomes destabilized. Exposure to flames, fires, and things like that can start that process of heating it and destabilizing it. It becomes self-reactive through thermal sources like a fire, and it will give off gases that are flammable and they will ignite. They will involve all of the oxygen that is in that chemical formula of the ammonium nitrate."
While some individuals on social media cast doubt over whether ammonium nitrate can produce such a powerful blast, history has shown it can.
In the video, Colonna points to two past deadly incidents in Texas alone. In 2013, ammonium nitrate was involved in an explosion that killed 15 people at a fertilizer storage and distribution facility in the town of West, just north of Waco. And in 1947, a fire aboard a ship carrying ammonium nitrate in the Port of Texas City triggered an explosion that killed over 500 people. The ship was carrying 2,300 tons of ammonium nitrate—less than what's being reported in Beirut.
Mitigating the hazard
Requirements for safely storing ammonium nitrate can be found in NFPA 400—specifically, in Chapter 11. They include, for example, outlining measures to ensure quantities are stored away from substances that can cause ammonium nitrate to destabilize and in facilities separated a safe distance from other structures and people.
"Chapter 11 imposes additional safeguards when you exceed 1,000 pounds," Colonna says. "From what I've read in the reports, they're talking something like 2,750 tons [in Beirut]. Clearly there should have been increased safeguards in the storage of that confiscated ammonium nitrate. You would have certain kinds of construction requirements, and you wouldn't have incompatible materials like oils and greases ... there would be separation distances, separation distances from the warehouse to an adjacent structure but also to populated areas."
The West, Texas, explosion in 2013 led to a number of updates to NFPA 400, which were highlighted in a May 2015 feature article in NFPA Journal. As the incident's five-year anniversary approached, however, some experts questioned whether enough had been done from a government regulation standpoint to prevent future similar incidents in the United States.
Another helpful tool for preventing fires or explosions involving not only ammonium nitrate, but also any hazardous material, is the NFPA Fire & Life Safety Ecosystem, which emphasizes the many moving parts and individuals involved in creating safe environments.
"All of this comes down to the Fire & Life Safety Ecosystem," Colonna says. "It starts with the government having requirements and then making sure those requirements are understood by everybody in the operational setting, whether it's the port managers or the warehouse managers, the people who are bringing the chemicals in and out of the area, or the public and first responders."
Watch the full interview with Colonna above, and learn more about NFPA 400 at nfpa.org/400.