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A valve designed to relieve the back pressure in a compressor, which helps to reduce the angle of attack of the rotor blades and prevent compressor stall and compressor surge. A bleed valve permits higher mass airflow through the compressor and reduces the mass flow through the combustion chambers and turbine. This minimizes the tendency to stall or surge. Also known as an air-release valve, a bleed valve, and a pop-off valve.