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Ammonium nitrate is a strong chemical oxidizer that can become an explosive under certain conditions.
Photo credit: Photo by Robert Burke
Ammonium nitrate and fuel oil mixtures are Class 1.4 explosives and may be encountered in bulk quantities in transportation.
Photo credit: Photo by Robert Burke
Explosives in the United States are regulated by the federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) in fixed storage and by the U.S. Department of Transportation (DOT) when in transit. Ammonium nitrate fertilizer is not regulated by the ATF because it is not an explosive.
Ammonium nitrate is regulated by the Department of Homeland Security (DHS) for security purposes.
DOT classifies ammonium nitrate as an oxidizer. The National Fire Protection Association (NFPA) covers storage requirements for ammonium nitrate and other chemicals in its Standard 400, Hazardous Materials Code.
Since the terrorist bombing of the Murrah Federal Building in Oklahoma City in 1995, DHS has monitored the storage and sale of bulk ammonium nitrate fertilizer used for agricultural purposes. This has led to a reduction in the amount of ammonium nitrate used by farmers and stored for sale by retailers across the country. It has also caused the retailers that still handle the product to be careful about information regarding its presence. It can only be sold to licensed farmers. (While conducting research for this article, I learned that according to the Nebraska Agri-Business Association Inc., 31 sites in the state store and sell ammonium nitrate fertilizer, but the association would not divulge the names or locations of those retailers. The association also advised me that if I happened to locate one of the retailers, it is likely I would be forbidden to take photographs or obtain any additional information. As I tried to contact retailers for this article, I found none who were willing to admit they had the ammonium nitrate, even though I talked to people who said they did. Though frustrating to me as a reporter, all of this is good because it would also make it very difficult for potential terrorists or criminals to gain access to the ammonium nitrate as easily as those who used it in Oklahoma City.)
The West, TX, tragedy
On April 17, 2013, a fire and subsequent explosion occurred at the West Fertilizer Co. in West, TX (see “Texas Tragedy” in the June 2013 issue of Firehouse®). Firefighters from the West Volunteer Fire Department were fighting a fire at the facility when the explosion occurred. Ammonium nitrate was located in a bin inside a seed and fertilizer building on the property. The explosion registered 2.1 on a seismograph reading in Hockley, TX, 142 miles away. Fifteen people, mostly emergency responders, were killed, more than 200 were injured and 150 buildings sustained damage.
Investigators confirmed that ammonium nitrate was the source of the explosion. According to the U.S. Environmental Protection Agency (EPA), there was a report of 240 tons of ammonium nitrate on the site in 2012. According to DHS, the company had not disclosed to the agency its ammonium nitrate stock. Federal law requires that DHS be notified whenever any facility has more than one ton of ammonium nitrate on hand, or 400 pounds if the ammonium nitrate is combined with combustible material.
The fire and explosion at the West facility were investigated by the U.S. Chemical Safety Board (CSB). Listed below are some of the observations and preliminary findings following the initial investigation (for a complete listing and to monitor the investigation of the West explosion, see www.csb.gov):
• The explosion resulted from an intense fire in a wooden warehouse building that led to the detonation of approximately 30 tons of ammonium nitrate stored inside the wooden bins. Not only were the warehouse and bins combustible, but the building contained significant amounts of combustible seeds, which likely contributed to the intensity of the fire.
• The building lacked a sprinkler system or other systems to automatically detect or suppress fire, especially when the building was unoccupied after hours. By the time firefighters reached the site, the fire was intense and out of control. The detonation occurred just 20 minutes after the first notification to the West Volunteer Fire Department.
• Although some U.S. distributors have built fire-resistant concrete structures for storing ammonium nitrate, fertilizer industry officials have reported to the CSB that wooden buildings are still the norm for the distribution of ammonium nitrate fertilizer across the U.S.
• No federal, state or local standards have been identified that restrict the sitting of ammonium nitrate storage facilities in the vicinity of homes, schools, businesses and healthcare facilities. In West, there were hundreds of such buildings within a mile radius, which were exposed to serious or life-threatening hazards when the explosion occurred.
• West volunteer firefighters were not made aware of the explosion hazard from ammonium nitrate stored at West Fertilizer and were caught in harm’s way when the blast occurred. The NFPA recommends that firefighters evacuate from ammonium nitrate fires of “massive and uncontrollable proportions.” DOT guidance contained in the Emergency Response Guidebook, which is widely used by firefighters, suggests fighting even large ammonium nitrate fertilizer fires by “flood(ing) the area with water from a distance.” However, the response guidance appears to be vague since terms such as “massive,” “uncontrollable,” “large” and “distance” are not clearly defined. All of these provisions should be reviewed by fire departments and other emergency response agencies in light of the West disaster to ensure that firefighters and other responders are adequately protected and are not put into danger protecting property alone.
Responders in agricultural communities should be aware of the types of fertilizers stored at local facilities. Ammonium nitrate is not one of the extremely hazardous substances covered by the Emergency Planning and Community Right to Know Act (EPCRA). However, fire departments have the right to information involving chemicals at a facility for the purposes of pre-planning, even if the chemicals are not regulated under the act. The State Emergency Response Commission (SERC) in each state and the Local Emergency Planning Committee (LEPC) may also be of assistance.
When responding to fixed-facility or transportation incidents in or around construction sites, mining operations or facilities that retail agricultural fertilizers, be on the lookout for explosives or chemical oxidizers such as ammonium nitrate or commercial-grade ammonium nitrate/fuel oil (ANFO). When responding to transportation incidents, always consider the possibility of explosives or oxidizers being present.
Fire is the principal cause of accidents involving explosive materials. Look for explosive signs, such as placards and labels. Evacuate the area according to the distances listed in the DOT Emergency Response Guidebook orange section. If no other evacuation information is available, a 2,000-foot minimum distance should be observed, according to the NFPA Fire Protection Handbook.
There is one rule of thumb in responding to incidents where explosives or chemical oxidizers are involved: Do not fight fires if the fire has reached the explosive storage area or cargo. The same applies to chemical oxidizers such as ammonium nitrate. n