A Study on Basic Test Parameters for Performance of Class D Extinguishers Against Lithium Metal Fires

The industrial demand for lithium metal is increasing rapidly; however, neither domestic nor international Class D fire extinguisher standards currently include performance test criteria specifically validated for lithium metal fires. In this study, the Korean Class D fire extinguisher standard was compared with UL 711 and ISO 7165 standards to derive candidate test conditions, and the combustion and extinguishing behavior of lithium was investigated on the basis of fire tests performed using lithium foil. Under the present test conditions, lithium foil fires showed a low heat release rate but sustained high temperatures over a prolonged period, and reignition triggered by deep-seated residual heat was identified as the principal hazard. A commercial copper powder-based Class D metal fire extinguisher by itself was insufficient to suppress reignition. However, the addition of excess copper powder led to a decrease in the heat release rate and temperature while suppressing reignition. Accordingly, the basic test parameters for evaluating the lithium fire-extinguishing performance—i.e., the specimen quantity, test frame dimensions, agent discharge time, and extinguishment criteria—were examined as candidate conditions for future verification studies.