used rotary air compressor remanufactured screw compressors copeland screw compressors USED ROTARY AIR COMPRESSOR Used rotary air compressor are generally single-speed devices: when on, they operate at a specific RPM (revolutions per minute) setting. One trick some manufacturers use to reduce costs is to create smaller used rotary air compressor that spin much faster, generating the same total volume (CFM) and pressure (PSI) at a much lower cost. The problem is, those high speeds can drastically reduce the lifespan of the used compressor. Lower speeds are also quieter. If comparing two used air compressors with similar ratings but different RPMs, the lower RPM option is probably a better choice for the long run.