An employee was pumping liquid propane from a propane delivery truck to a storage tank. After the transfer was completed, the employee closed the valves and disconnected the transfer hose. During the transfer, the liquid propane auto-refrigerated the riser pipe of the storage tank and that delayed the vaporization of the propane. Upon reaching a higher temperature, liquified propane began rapidly expanding. Liquid propane then discharged from the pipe and contacted the employee, causing cold burns. The employee was hospitalized for second-degree burns to their torso and arms.