The gas mixing system works by metering three gas supplies into a common mixing tank. The mixture is then bubbled through alcohol in a tank within a small refrigerator which has been modified for safe operation in a flammable gas system. Because the gas Flow, not the pressure, is regulated by the metering systems, pressure and provided feedback to the flow-control system, The mixing, bubbling, and pressure control systems are all built into the same relay rack. They are collectively referred to as the Gas Mixing Station.