A pivoting vane rotary compressor includes a housing having a generally pear-shaped chamber. A rotor mounted within the chamber defines a main and constricted chamber regions. Reversible intake and exhaust ports alternately introduce air into and exhaust air from the chamber. The rotor carries pivotable vanes and a motor drives the rotor alternately in opposing first and second directions to open the vanes and define compartments that transmit the air through the chamber between the ports. Air introduced through one of the ports is compressed and discharged through the other port. A concentrator employs a pair of these compressors as well as associated filters and crossover valves.