This module includes detailed information on compression ratio and volumetric efficiency. Practical examples a d solutions are included to help the reader understand why some systems are more efficient than others. The discharge and suction strokes of reciprocating compressors and how they relate to compression ratio and volumetric efficiency are explained. Compressor performance curves and graphs, compressor specifications, parallel compressors and their oil systems are also explained in detail. Coltage variation is explained as it applies to compressors. A solid understanding of the compression system is necessary to successfully perform field service.