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U.S. Department of Health and Human Services

Recognized Consensus Standards: Medical Devices

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Part B: Supplementary Information Sheet (SIS)
FR Recognition List Number 062 Date of Entry 05/29/2024 
FR Recognition Number 1-167
CGA  V-5:2019
Diameter-Index Safety System (Noninterchangeable Low Pressure Connections for Medical Gas Applications)
The administration of medical gases to patients is subject to a variety of hazards that can result from human error due to preoccupation, a mental lapse, or carelessness. This publication was developed to reduce the possibility of inadvertent substitution of the wrong medical gases by personnel when using equipment for administering anesthesia, resuscitation, and therapy.

CGA V-1, Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections, establishes assigned standard connections for threaded outlets on cylinder valves, which results in the removal from service of all cylinder valves having nonconforming threaded outlets. CGA V-1 also describes the details of the Pin Index Safety System for flush-type medical gas cylinder valves. This system reduces the possibility of inadvertent substitution of the wrong gases on equipment with yoke-type connections. The Pin Index Safety System has been adopted by national and international standards organizations including the Canadian Standards Association (CSA) and the International Organization for Standardization (ISO).

The Diameter Index Safety System defines noninterchangeable removable connections for use with medical gases at pressures of 200 psi (1380 kPa) or less. Removable, threaded connections are readily and commonly engaged or disengaged in routine use and service and are often found on regulators, resuscitation equipment, anesthesia equipment, therapy equipment, and other similar equipment.

The Diameter Index Safety System supplements but does not replace:
- any of the means for medical gas identification currently in use;
- the Pin Index Safety System;
- the existing threaded outlet standards for cylinder valves; or
- automatic quick coupler valves that also provide noninterchangeable connections for medical gases and suction equipment.
Extent of Recognition
Complete standard
Rationale for Recognition
This standard is relevant to medical devices and is recognized on its scientific and technical merit and/or because it supports existing regulatory policies.
Transition Period
FDA recognition of CGA V-5:2008 (Reaffirmed 2013) [Rec# 1-81] will be superseded by recognition of CGA V-5:2019 [Rec# 1-167]. FDA will accept declarations of conformity, in support of premarket submissions, to [Rec# 1-81] until July 5, 2026. After this transition period, declarations of conformity to [Rec# 1-81] will not be accepted.
Public Law, CFR Citation(s) and Procode(s)*
Regulation Number Device Name Device Class Product Code
§868.2700 Regulator, Pressure, Gas Cylinder Class 1 CAN
§868.5160 Gas-Machine, Anesthesia Class 2 BSZ
§868.5925 Ventilator, Emergency, Powered (Resuscitator) Class 2 BTL
Relevant FDA Guidance and/or Supportive Publications*
Appropriate Use of Voluntary Consensus Standards in Premarket Submissions for Medical Devices - Guidance for Industry and Food and Drug Administration Staff, issued September 2018.
FDA Technical Contact
 Benjamin Sommerkorn
Standards Development Organization
CGA Compressed Gas Associated, Incorporated https://www.cganet.com/
FDA Specialty Task Group (STG)
*These are provided as examples and others may be applicable.