Reciprocating single acting compressors are generally of one-stage or two-stage design. Compressors can be of a lubricated or oil-less design. 

In the single-stage compressor, air is drawn in from the atmosphere and compressed to final pressure in a single stroke. The single-stage reciprocating compressor is illustrated in the Figure below. Single Stage compressors are generally used for pressures of 70 psi (pounds per square inch) to 135 psi. 

In the two-stage compressor, air is drawn in from the atmosphere and compressed to an intermediate pressure in the first stage. Most of that heat of compression is removed as the compressed air then passes through the intercooler to the second stage, where it is compressed to final pressure. The two-stage reciprocating compressor is illustrated in the Figure below. Single and two stage reciprocating compressors are frequently used in auto and truck repair shops, body shops, service business, and industrial plants.