AT THE FIRE AND SUBSEQUENT EXPLOSION of the West Fertilizer Company ammonium nitrate storage facility in West, Texas, in 2013, nearly every home or structure within a 1,500-foot radius of the blast site was damaged or destroyed. The incident highlighted the need for public notification/alert capabilities in communities where AN storage facilities are located and was a topic of discussion for the Technical Committee on Hazardous Chemicals, which is responsible for NFPA 400, Hazardous Materials Code.
As a result, the 2016 edition of NFPA 400 will include new requirements for approved public notification/alert systems for AN facilities. The systems must be capable of immediately notifying individuals located within a one-mile radius of the facility of the need to evacuate when an ammonium nitrate fire occurs. The notification system could be a reverse 911 or a siren.
All new and existing facilities with Type III, IV, or V construction—building types that permit the use of combustible construction—or that contain combustible content are required to have this notification system. The safe evacuation distance of one mile is the default distance unless a facility has an analysis approved by an authority having jurisdiction that takes into consideration the amount and configuration of stored ammonium nitrate in the facility.
The committee selected the one-mile evacuation distance based on information provided by the Institute of Makers of Explosives (IME), the safety association of the commercial explosives industry in the United States and Canada. Using a risk assessment tool that calculates risk to personnel from explosives facilities, IME conducted an analysis of the debris patterns of storage facilities containing 50,000 pounds and 1 million pounds of ammonium nitrate. The one-mile evacuation distance was based on the greatest debris throw from the faces of the storage facility where the probability of anyone being killed from an event would be less that one in a million.
Additionally, a recent project by the Fire Protection Research Foundation looked at separation distances and included full-scale tests using ammonium nitrate. The project was designed to assist the NFPA 400 committee and other NFPA committees dealing with questions related to establishing separation distances. The final report, “Separation Distances in NFPA Codes and Standards,” is available online.