Pin Index Safety System

The Pin Index Safety System, or PISS, is a safety system that uses geometric features on the yoke to ensure that pneumatic connections between a gas cylinder and a machine that uses pressurized gases are not connected to the wrong gas yoke. This system can be seen on an anesthesia machine.

Each gas cylinder has a pin configuration to fit its respective gas yoke. Refer to the figure on the right; units are in millimeters.

O2: 2-5
N2O: 3-5
Air: 1-5
CO2: 1-6
Heliox: 2-4

[edit] Standards
International (ISO) and European (CEN) Standard
EN ISO 407 : Small medical gas cylinders - Pin-index yoke-type valve connections
PIN Index Entonox=7