HFC134 (aka HFC134a) is the weaker of two propellants used in Airsoft gas guns. The other, HFC22, is considerably more powerful. A particularly confusing aspect of this is that both are known as "Green Gas", though HFC22 is more commonly know by that name. Many beginning airsofters confuse the two types of gasses, and use HFC22 gas a a gun meant for HFC134. The rule of thumb is if your gun has a metal slide, you can use HFC22. Typically, Taiwanese GBB airsoft guns (such as KWC and KJW) use HFC22, while the Japanese (Tokyo Marui, Western Arms) use HFC134. Using HFC22 in an airsoft gun meant for HFC134 will significantly lower its lifespan. Propellants
