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. It has no other purpose to the valve other than offering a physical barrier to connecting the wrong cylinder.

Pin index configurations

Each gas cylinder has a pin configuration to fit its respective gas yoke. Refer to the diagram for pin numbers; dimensions are in millimeters.

O₂: 2,5^[1]^[2]
N₂O: 3,5^[1]^[2]
Mixture of O₂ and N₂O (50% / 50%): 7 (a single pin, located in the centre)
Air: 1-5^[2]
Mixtures of CO₂ and O₂ with more than 7% CO₂: 1,6^[1]
Mixtures of CO₂ and O₂ with less than 7% CO₂: 2,6^[1]
He: No pin
Mixtures of O₂ and He with less than 80% He, commonly called Heliox): 2,4^[1]
Mixtures of O₂ and He with more than 80% He: 4-6^[1]
Cyclopropane: 3,6^[1]
Ethylene: 1,3^[1]
Nitrogen: 1-4

Standards

International (ISO) and European (CEN) Standard

EN ISO 407 : Small medical gas cylinders - Pin-index yoke-type valve connections

The pin index system is a safety system (PISS) designed to ensure the correct gas is filled into the correct cylinder, and that the cylinder will only connect to the correct equipment. The positions of the holes on the cylinder valve correspond with the pins fitted to the yoke attached to the equipment. The pin positions for each medical gas are unique. If an attempt is made to fit the wrong gas cylinder to the yoke a tight seal will not be made, as the pins cannot locate.

Safety

It is possible to bypass the pin-index system if the pins are removed.

References

^ ^a ^b ^c ^d ^e ^f ^g ^h "Attaching Therapy Equipment: Pin Index Safety System work=Medical Gases and Safety Systems: CRC 330" (PDF). Cardiorespiratory Care, University of South Alabama. Retrieved 12 August 2017. {{cite web}}: Missing pipe in: |title= (help)
^ ^a ^b ^c Dosch, Michael P.; Tharp, Darin. The Anesthesia Gas Machine. University of Detroit https://healthprofessions.udmercy.edu/academics/na/agm/03.htm. Retrieved 12 August 2017. {{cite web}}: Missing or empty |title= (help)

[pin_code-1] ^ ^a ^b ^c ^d ^e ^f ^g ^h "Attaching Therapy Equipment: Pin Index Safety System work=Medical Gases and Safety Systems: CRC 330" (PDF). Cardiorespiratory Care, University of South Alabama. Retrieved 12 August 2017. {{cite web}}: Missing pipe in: |title= (help)

[pin_code_2-2] Dosch, Michael P.; Tharp, Darin. The Anesthesia Gas Machine. University of Detroit https://healthprofessions.udmercy.edu/academics/na/agm/03.htm. Retrieved 12 August 2017. {{cite web}}: Missing or empty |title= (help)

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