Permanent gases such as nitrogen, air and argon can be used as oxygen valves. However, some gases, such as ammonia and other corrosive gases, need special pressure reducing valves. Common in the market are special pressure reducing valves such as nitrogen, air, hydrogen, ammonia, acetylene, propane and water vapor. The use methods and precautions of these pressure reducing valves are basically the same as those in oxygen valves. But it should also be pointed out that other gases generally do not use special pressure reducing valves. In order to prevent misuse, some special pressure reducing valves adopt special connection ports between cylinders. For example, both hydrogen and propane use left thread, which is also called reverse thread. Pay special attention when installing.