A device used in fuel handling systems to purge the air from fueling lines. 

As the fueling process begins, hoses and other lines are often filled with air, not with liquid. When liquid starts to flow, air present in the line collects in pockets. This can create a jarring, erratic effect that will continue until the flow of liquid has finally purged all the air pockets in the line. 

Because liquid fuel meters will measure the movement of air and vapor, as well as the movement of liquid fuel, air and vapor must be vented from the piping before the liquid enters the meter. This is the primary function of the air eliminator. Air elimination devices are designed to quickly bleed air and vapors from the fuel lines and to thus allow liquid product to flow freely.