Green Gas

Green Gas is a propellant for airsoft guns, used as an alternative source of power to spring- or motor-driven airsoft weapons.

In 2004, Carlton Chong, of Airsoft Innovations, determined through gas chromatography analysis that green gas is in fact a mixture of propane, silicon oil and odor 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 because the solution is cheaper and more widely available than 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.

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Wikipedia