Fast Idle Air Valve

fast idle
When the engine is cold, it needs to run faster to keep it from stalling. A cam on the Carburetor forces the Throttle open a little more when the Choke is engaged.

air valve
A valve controlling the passage of air. Also a valve admitting air to a steam boiler, preventing the formation of a partial vacuum when the steam condenses.
Control valve in an air system for setting volume and pressure.
A valve mounted on top of a tank car through which air pressure (or other gas pressure) is introduced to facilitate unloading.