A21F, A21H-C is suitable for operating temperatures less than 200 degrees in the air, equipment or pipeline ammonia, LPG media. A21W-P, R type is suitable for a temperature of 200 degrees or less corrosive gas or liquid equipment or pipeline, as the overpressure protection device. KA21Y is suitable for a temperature of less than or equal to 100 degrees of liquefied petroleum gas.