Tokheim Flame Arresters are designed to be used at the termination of a vent pipe, which vents volatile vapors directly into the atmosphere. Vapors passing through the stack, if ignited from an outside source, will burn like a gas water heater or furnace. The fire cannot flash through the Plate Stacks into the tank. The "Plate Stacks" are protected from the elements, by an aluminum weather shield. If a fire were to occur, fusible links drop the weather shield at 165 degrees F., allowing the flame to propagate upwards and away from the Flame Arrester. When the pressure inside the tank diminishes, the fire will die out, much like shutting off the valve on a water heater or furnace. Tokheim Flame Arresters are U/L listed. Series 85 Flame Arresters are NOT appropriate for Class B gasses.