Abstract: An air inlet valve assembly for a rotary scroll compressor is disclosed. The rotary scroll compressor includes stationary and orbiting scroll elements which are intermeshed and nested to form at least one spiraling compression pocket therebetween, a drive mechanism drives the orbiting scroll element in an orbit about the stationary scroll element, and an anti-rotation bearing device maintains the orbiting scroll element substantially non-rotational with respect to the stationary scroll element. The air inlet valve assembly supplies an uncompressed gas (e.g., ambient air) to the compression apparatus and prevents backward rotation of the orbiting scroll element when power to the drive mechanism is terminated. The air inlet valve assembly includes a valve piston positioned within an air intake channel leading to the suction region of the rotary scroll compressor, the valve piston having a first position blocking the air intake channel and a second position unblocking the air intake channel.