Defines flow-metering devices which are connected and disconnected by the operator at terminal units of a medical gas pipeline system for measurement and delivery of medical gases, they can be connected either directly or by means of flexible connecting assemblies. Applicable only to flow-metering devices for the following medical gases; nitrous oxide, oxygen, carbon dioxide, air for breathing, xenon, helium, oxygen/nitrous oxide mixture (50% / 50% V/V), specified mixtures of the gases listed above. Excluded are electrical or electronic flow-metering devices.