Abstract: The fire extinguishing characteristics of the gas extinguishing agent on 18650 ternary lithium ion batteries fire in the low- pressure of air cargo and normal- pressure environment was researched. Based on the low- pressure experimental chamber and the gas fire extinguishing system, perfluorohexanone was used to extinguish the thermal runaway of lithium ion batteries at 101 kPa of normal pressure and 30 kPa of low pressure. Fire extinguishing phenomenon and temperature changes were recorded and changes in relevant gas components in the air were analyzed. The results showed that thermal runaway under normal pressure manifests as outward deflagration and continuous open flame combustion, thus prolonging the fire extinguishing time. The low-pressure and low-oxygen concentration environment slowed the thermal runaway combustion exothermic reaction of the lithium ion batteries and helped control the peak temperature, improved the efficiency of fire extinguishing. In the process of fire extinguishing, the extinguishing agent would increase the consumption of oxygen, and the oxygen consumption at low pressure is greater than normal pressure. The internal reaction and secondary combustion of the batteries are more sufficient under normal pressure, releasing more heat outward and generating more carbon dioxide, while more carbon monoxide is produced at low pressure.

Key words: normal- pressure, low- pressure, lithium ion battery, extinguishing, temperature characteristics, gas component