A reciprocating atmosphere compressor is a positive displacement compressor that uses a crankshaft-driven Piston Air Compressor piston and cylinder to compress the air. … A two-stage compressor includes an additional step where the atmosphere is compressed by another, smaller sized piston to a pressure as high as 175 PSI.

Like a little internal combustion engine, a conventional piston compressor includes a crankshaft, a connecting rod and piston, a cylinder and a valve head. … As the piston movements down, a vacuum is created above it. This enables outside atmosphere at atmospheric pressure to force open up the inlet valve and fill up the region above the piston.