Compressed Air

The compression of air for medium flows and pressures is typically done through a lubricated screw compressor, which belongs to the family of positive displacement compressors. This process is very robust and has low maintenance costs. However, depending on the application, the final product must be treated to remove oil, water, and residual dirt from the process.

Pressure Swing Adsorption (PSA)

The generation of oxygen and nitrogen is typically done through a cryogenic process that consists of "liquefying" the air by drastically lowering its temperature.
This process requires economies of scale to be efficient and also requires the commercialization of all the "liquefied" components of the air (approx. 78% Nitrogen, 21% Oxygen, 1% Argon) to make the energy consumption profitable.
A more recent technology is PSA, which does not require economies of scale or the commercialization of other gases to be efficient (there are generators for personal use), since it operates at room temperature and uses the principle of molecular adsorption to separate the components of the air.