# DISS connector (Diameter Index Safety System)

Under CGA V-5, the Compressed Gas Association standard (7th edition, 2019, reaffirmed 2026), a DISS (Diameter Index Safety System) connector is a non-interchangeable, removable medical gas connection for use at pressures of 200 psi (1380 kPa) or less.

The CGA abstract of V-5 notes that removable, threaded connections are readily and commonly engaged or disengaged in routine use and service and are often found on regulators, resuscitation, anaesthesia and therapy equipment. The system supplements, but does not replace, the means of medical gas identification in use, the Pin Index Safety System, the threaded outlet standards for cylinder valves and automatic quick coupler valves, and CGA does not designate where it should be applied.

The WHO Foundations of medical oxygen systems (2023) lists DISS among several connector styles, alongside AFNOR, DIN, BS, JIS, AS and AGA, each with its own non-interchangeable, key-like indexing. For the ISO screw-threaded type, see [NIST connector](https://library.ultracontrolo.com/glossary/nist-connector/). Ultra Controlo wall outlets (Type B) are available in "Schraeder", NIST, DISS and DIN configurations, and its medical oxygen and air flowmeters connect directly to NIST, DISS and "Schraeder" outlets.

## Sources

- [CGA V-5, Standard for Diameter Index Safety System, abstract and publication details (Compressed Gas Association)](https://legacy.cganet.com/Publication/Details.aspx?id=V-5)
- [WHO, Foundations of medical oxygen systems (2023), section 2.9.2](https://iris.who.int/server/api/core/bitstreams/4ad6f5fd-089e-4142-8439-b64e98d816d8/content)
- [Ultra Controlo, medical gas wall outlets (Type B)](https://www.ultracontrolo.com/accessories/medical-gas-outlets-2)
- [Ultra Controlo, medical oxygen and air flowmeter](https://www.ultracontrolo.com/accessories/flowmeter)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/glossary/diss-connector/