Chemicals

Fertile Soil for Safety: OSHA, EPA, and Industry Address Fertilizer Safety

On April 17, 2013, fire broke out in a wooden warehouse at West Fertilizer Company in West, Texas. As the town’s volunteer fire department mobilized to respond, 30 tons of ammonium nitrate (AN) fertilizer in an adjacent wooden warehouse exploded. Fifteen people died, including 12 volunteer firefighters. An apartment building, many houses, and a nursing home were destroyed, and a local school was damaged. In the wake of the incident, President Obama signed Executive Order 13650, requiring federal agencies to take action on the subject of fertilizer safety.

To that end, federal OSHA, the EPA, and the Fertilizer Safety and Health Partners (a group made up of affected parties) signed an alliance agreement on February 2, 2015, that will enable the agencies to work together to provide safety and health information and training resources to workers, emergency responders, and communities surrounding establishments in the agricultural retail and supply industry. The alliance will focus on the safe storage and handling of fertilizers such as AN and anhydrous ammonia.


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Hazards of AN

The alliance has not yet had a chance to develop any materials, but that doesn’t mean that no guidance is available. In fact, OSHA already has a standard that applies to the storage of AN, and OSHA, the EPA, and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) issued a Chemical Advisory on the Safe Storage, Handling and Management of Ammonium Nitrate under EPA’s Risk Management Program in August 2013.

According to the Chemical Advisory, pure AN is highly stable and unlikely to explode. However, if it is mixed or even contaminated with combustible materials, including sugar, grain dust, seed husks, or other organic materials, even in fairly low percentages, it becomes far more dangerous. AN with more than 0.2 percent combustible substances is classified by the DOT as an explosive.


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Storing AN near combustible materials—not only grain and sawdust but also petroleum chemicals—is also extremely dangerous. AN that contains less than 0.2 percent combustible substances, and AN fertilizers, are classified by the U.S. Department of Transportation (DOT) as oxidizers. Because AN is a powerful oxidizer and a rich source of nitrate, the presence of fuel and/or heat (and especially both) near AN is a very high-hazard situation.

Another high-risk situation occurs when AN is compressed. According to the National Fire Protection Association (NFPA), AN is far more likely to undergo detonation, explosive decomposition, or explosive reaction when confined in high temperatures or exposed to shock, especially when contaminants are present or it is under confinement. Under some conditions, AN can self-compress or self-confine, making careful storage and management necessary.

Tomorrow, we’ll look at what the OSHA standard has to say about AN storage.