Flammability potential of halogenated fire suppression agents and refrigerants

Abstract Halogenated hydrocarbons are often used as fire suppression agents or refrigerants due to their low‐ or no‐flammability potential at atmospheric pressure and room temperature. However, these substances can form highly flammable mixtures with air at sufficiently high pressures—even at room temperature, and in the absence of other flammable vapors. General flammability behavior indicates that there is a critical pressure (also referred to in the literature as the pressure limit of flammability), below which all possible mixtures of the Agent and air are non‐flammable. Above the critical pressure, a range of mixtures are explosible at room temperature. While this behavior does not affect the intended use and performance of these agents, recognizing this property, and determining the critical pressure are vital to establishing safety procedures that can avoid accidental explosions. This paper presents an analysis, supporting data, and a screening method to evaluate the explosibility potential that may arise from deliberate or unintentional elevated pressure handling of refrigerants and fire protection agents. The data and the accompanying analysis suggests that even a fire protection agent such as HFC‐227ea may form an explosible mixture with air at room temperature if the pressure is above approximately 60 psig. There is a definite need for the systematic characterization of refrigerant and fire protection agent flammability at elevated pressures, using appropriate experimental techniques discussed in the text.