Is ammonium nitrate safe to store?

Before a large amount of ammonium nitrate fertilizer exploded recently in Beirut, Lebanon, many people were unaware of how dangerous the compound can be. The fertilizer is an odorless, crystalline material that is also used as an industrial explosive.

You may be familiar with the 2013 Texas fertilizer plant explosion that killed 15 people. That involved ammonium nitrate and was ruled deliberate. Also, two tons of ammonium nitrate were used to create the bomb in the 1995 Oklahoma City bombing that killed 168 people.

According to the Lebanese prime minister, approximately 2,750 metric tons of ammonium nitrate were stored for years in a portside warehouse in Beirut before the explosion, which killed dozens and caused widespread property damage.

A useful tool when stored carefully

Ammonium nitrate is used as fertilizer and an industrial explosive, and our world would be very different if it were not available.

The issue is that ammonium nitrate has dangerous properties. For one thing, it can create a potent explosive when mixed with fuel oils. For another, it is an oxidizer, which means that it intensifies combustion and helps other substances ignite.

When stored properly, it is not itself especially combustible. However, the storage rules are strict and may not have been followed in the Beirut warehouse. Ammonium nitrate must be kept away from heat, flames and fuels. In much of the European Union, ammonium nitrate cannot be stored without first being mixed with calcium carbonate, which creates a safer compound.

In the U.S., facilities that store over 2,000 pounds of ammonium nitrate are subject to inspections under the Chemical Facility Anti-Terrorism Standards.

However useful, ammonium nitrate is dangerous. While the government can issue standards for proper storage in a cool, dry, fuel-free environment, the burden falls on companies to comply with or exceed those standards. If they fail to do so, it may be necessary to hold those companies responsible.

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