Positive Displacement Compressors

Positive displacement compressors suck a specific quantity of air into a cylinder.  The piston then compresses it.  The output of a positive displacement compressor is always.

Examples of positive displacement compressors are Reciprocating Piston compressors, Rotary Screw compressors, Scroll compressors and Rotary Vane compressors.

Positive displacement compressors can build very high pressures.  The downsides are high noise, lesser efficiency, leakages from the seals and frequent maintenance.