A compressor for gaseous fluids comprises a positive displacement gear pump, as typically used for liquid transfer, modified to effect compression of gases. The pump inlet includes a main inlet plus multiple secondary inlets feeding inlet gases to gear voids spaced from and moving away from the main inlet. The pump outlet includes a main outlet plus multiple feedback passages feeding partially pressurized outlet gases to gear voids spaced from and moving toward the main outlet. The supplemental inlets and feedback passages increase both the throughput of the compressor and the amount of compression imparted to the gases.