ISO 2503:2009 specifies requirements for single or two-stage pressure regulators without flow-metering devices for connection to gas cylinders used forcompressed gases up to 300 bar (30 MPa),dissolved acetylene,liquefied petroleum gases (LPG),methylacetylene‑propadiene mixtures (MPS), andcarbon dioxide (CO2),for use in welding, cutting and allied processes. It does not cover pressure regulators having a nominal outlet pressure p2 > 20 bar.ISO 2503:2009 also specifies requirements for single or two-stage pressure regulators with flow-metering devices for connection to gas cylinders used forcompressed gases or mixtures up to 300 bar (30 MPa), andcarbon dioxide (CO2),for use in welding, cutting and allied processes. Typical processes using this equipment are: tungsten inert-gas arc welding (TIG), metal-arc inert-gas welding (MIG), metal-arc active-gas welding (MAG), plasma arc welding, tubular-cored-wiretubular-cored-wire welding and plasma cutting. Annex B gives examples of flow-control systems and their flow-measuring devices.