Critical variables associated with the hazard classification of Ammonium Nitrate

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Ammonium Nitrate (AN) “is a chemical compound produced in both solid and liquid forms that is commonly used in fertilizers” [1]. 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. For example, in 2013 a fire broke out at an ammonium nitrate plant in West, Texas that ultimately caused a massive explosion culminating in the deaths of 15 people, mostly first responders. On the other hand a similar fire at an Ammonium Nitrate storage facility in Athens, Texas simply burned itself out without the help of firefighters [2]. The different behaviors of AN in different fire situations make it difficult to determine the correct classification of AN. Similarly, there exist discrepancies between the NFPA and International Fire Code (IFC) classifications of Ammonium Nitrate. As a result there is a need for sufficient data to assist in the proper classification 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 result in future Ammonium Nitrate testing.

Research goal: The purpose of this project is to summarize the available information on the different forms of Ammonium Nitrate and how they are classified. This will be accomplished through a two-step literature review: summarizing the available information on AN classification from chemistry and codebased documentation, and identifying critical variables which led to AN instability from existing test data and results. The deliverables from this project will be of direct use to the NFPA 400, Hazardous Materials Code Technical Committee.

Download the project summary. (PDF)