Multi staging is simply the compression of air or gas in two or more cylinders in place of a single cylinder compressor. Multistage compression refers to the compression process completed in more than one stage i.e. a part of compression occurs in one cylinder ( L.P. cylinder) and subsequently compressed air is sent to subsequent cylinders ( H.P. cylinder) for further compression.

Merits of multistage compressor over single stage compressor.

1. Reduced work of compression per kg of air

2. Wall thickness of L.P. cylinder is reduced, since it has to withstand lower pressures. This makes compressor lighter and cheaper.

3. Volumetric efficiency of compressor increases due to reduced pressure ratio in each stage.

4. Temperature at end of compression would be less. As a result lubrication would be effective. Hence, compressor life increases.

5. Leakages past the piston are reduced

6. Operating cost is reduced

7. It gives more uniform torque, hence size of flywheel is reduced.