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Variables Associated with the Classification of Ammonium Nitrate - A Literature Review

Fire Protection Research Foundation report: "Variables Associated with the Classification of Ammonium Nitrate - A Literature Review"
Author: Sean Gillis, Sreenivasan Ranganathan, Fire Protection Research Foundation, Quincy, MA
Date of issue: March 2017


Introduction

Ammonium Nitrate (AN) “is a chemical compound produced in both solid and liquid forms that is commonly used in fertilizers”. The burning rate of technical-grade AN prill falls within the Class 2 oxidizer criteria in Annex G of NFPA 400, 2016. The loss history of AN also indicates potential for unstable reactive hazard properties, uncontrolled decomposition and/or detonation under circumstances that are not fully understood. In the most recent revision of NFPA 400, Hazardous Materials Code, the Technical Committee (TC) classified Ammonium Nitrate as a Class 2 Oxidizer. However recent hazardous material incidents involving AN have resulted in differing views regarding the reactivity of the compound and whether or not it should be considered an unstable reactive in NFPA 400. The different behaviors of AN in different fire situations make it difficult to determine the appropriate safe practices for AN storage and handling. There are also discrepancies between the NFPA and International Fire Code (IFC) classifications of Ammonium Nitrate. As a result there is a need for additional data to assist in the proper classification/treatment of AN. An examination of existing data involving the reactivity of AN will assist the NFPA 400 TC in determining the appropriate classification of Ammonium Nitrate, and perhaps point to a need for future Ammonium Nitrate testing.