Green Gas is used as a propellant for airsoft guns. It is an alternative source of power as opposed to spring- or motor-driven airsoft weapons.
In 2004, it was determined by Carlton Chong (of Airsoft Innovations) through gas chromatograph analysis that green gas is in fact a mixture of propane, silicon oil, and odour modificants. This discovery prompted his development of a propane adaptor, allowing users to administer their own green gas derivatives using retail propane and silicone oil.
Since green gas' analysis, other manufacturers have also begun to produce adapters that attach to propane tanks available at many retail stores. These sometimes include reservoirs to store lubricant (usually silicone oil). The propane option has become popular due to the fact that the solution is cheaper than Green Gas, as well as being more widely available compared to Green Gas. Although propane alone does not have lubrication in the propellant, proponents of using propane instead of green gas state that this can be remedied by manual lubrication of internal parts before use of the gun.