Low Pressure Carburizing ( LPC) or Vacuum Carburizing is newly developed over last ten years. It has been a mature technology and widen application on the heat treatment to replace the traditional atmosphere. High Pressure Gas Quenching (HPGQ) is one optimum process to control the distortion with the excellence of part cleanness. LPC and HPGQ amplify the technology by each other. The combination of LPC and HPGQ is the most perfect solution for case hardening process so far. Three chamber structures are the classic design for such furnaces.