The Micro Oil Screw Air Compressor uses two rotors (screws) that rotate in opposite directions. As the screws turn, air is drawn in and compressed. The oil injected into the system lubricates and cools the compressor element while also sealing the gap between the screws.
[pdf] A portable/towable rotary screw diesel air compressor capable of around 180-260CFM costs approximately $14,000 to $20,000. A heavy duty turbocharged diesel compressor designed for mining, railroad, and heavy-duty construction might cost $25,000 to $30,000 or more.
[pdf] Most simply, air compressors work by doing exactly what it sounds like they do – they make use of air pressure to get the job done. First, they compress air it into a smaller volume from what it originally was. Onc.
[pdf] 
