What is the maximum pressure to which air can be compressed?

Answer 1

Air starts liquefying at about 330 atm., at ambient temperature.

Answer 2

High pressure air system used for starting diesel engines can be 3000psi. SCUBA compressors for recharging tanks may be as high as 6000psi.

3000 psi air is used in the manufacturing of liquid Air and its major components Nitrogen Oxygen and Argon. Liquid air uses a portion of the compressed air to cool the remaining volume through cooling by expansion. So a combination of pressure and low temperatures are used in the liquefaction process.

Since SCUBA systems are at nearly twice the pressure found in liquid air production it is obvious that the combination of pressure and low temperature is required for air liquefaction.

As pressure increases in a compressor so do the mechanical requirements of not only the compressor but the piping system as well. I suspect that mechanical limitations (as well as safety) of the compressor are limiting factors in practical compressed air maximum pressure.

So I would say 6000psi as a practical limit

Answer 3

Not sure of the pressure ( it will depend on temperature)but any gas can only be compressed until it becomes liquid.
Liquids are incompressible. This is why hydraulic systems can work.

Answer 4

The MAX pressuer would be determined by the compression equipment and the Strength of the materials to make them.