Scope: This document specifies the design, construction, type testing, and marking requirements for pressure regulators (as defined in 3.18) intended for the administration of medical gases and their mixtures in the treatment, management, diagnostic evaluation and care of patients or for gases used for driving surgical tools. Examples of gases include oxygen, medical air and oxygen/nitrous oxide mixtures. This document applies to pressure regulators: a) intended to be connected to cylinders by the operator; b) with integral flow-metering devices intended to be connected to cylinders by the operator; c) that are an integral part of medical equipment (e.g. anaesthetic workstations, lung ventilators, resuscitators). A pressure regulator can be provided with pressure outlet or flow outlet, and can be adjustable or pre-set. Pressure regulators are intended to be fitted to refillable cylinders with a working pressure up to 30 000 kPa ( 300 bar) and can be provided with devices which control and measure the flow of the medical gas delivered.