A compressor is a machine that increases the pressure of a gas by bringing down its volume. An air compressor is a type of gas compressor that converts power into some possible energy stored in compressed air. There are many types of compressors, which are as follows:

Positive Displacement, Dynamic and hermetically sealed, open or semi-hermetic. Again the Positive Displacement and Dynamic compressors are subdivided into the following heads:

Positive displacement:
a. Reciprocating compressors
b. Ionic liquid piston compressor
c. Rotary screw compressors
d. Rotary vane compressors
e. Rolling piston
f. Scroll compressors
g. Diaphragm compressors

Dynamic compressor
a. Air bubble compressor
b. Centrifugal compressors
c. Diagonal or mixed-flow compressors
d. Axial-flow compressors

Applications of compressors:
Applications of gas compressors are manifold.

a. Compressors are used to transfer purified natural gas from the production site to the consumer point.

b. Compressors are used in many plants like Petroleum refineries, natural gas processing plants, petrochemical and chemical plants and similar other plants.

c. Compressors are used in refrigerators and air conditioners to move heat.

d. In order to fill high pressure cylinders required for medical, welding and other uses, compressors are needed.

e. Compressors are required in the manufacturing and blow moulding of PET plastic bottles and containers.