A reciprocating air compressor is a positive Piston Air Compressor displacement compressor that runs on the crankshaft-driven piston and cylinder to compress the air. … A two-stage compressor contains an additional step where the air flow is compressed by a second, smaller piston to a pressure of up to 175 PSI.

Like a small internal combustion engine, a conventional piston compressor includes a crankshaft, a connecting rod and piston, a cylinder and a valve head. … As the piston moves down, a vacuum is created above it. This allows outside surroundings at atmospheric pressure to drive open up the inlet valve and fill up the area above the piston.