The leading fields would rent or buy compressors or high pressure nitrogen tanks to fill from if they wanted to offer 4500 psi. Then along came the booster. This is a look at one model of booster. With the necessary hoses, valves and regulators, it weighs about 33 pounds. To understand how the booster works, think about how to get high pressure air.
Air is put into a container, and the volume of air is made smaller.
The more compressed the air, the higher the pressure. A compressor is basically a cylinder with a moveable piston. Add check valves and the air only flows in one direction. When the piston is pulled outward, air enters the cylinder through one check valve. When the piston is pushed in, the air is compressed and flows out through the second valve into a container such as a bottle.