Gaspers usually receive their air from the AC PACKs aboard the aircraft, which in turn receive compressed, clean air from the compressor stages of the aircraft's jet engines or when on the ground from the auxiliary power unit (APU) or a ground source. A master control for gaspers is located in the cockpit; gaspers are often temporarily turned off during certain phases of flight (e.g. during take-off and climb) when the load on the engines from bleed-air demands must be minimized.