UL 252:2017 Compressed Gas Regulators.
1.1 These requirements cover regulators used to reduce the pressure of compressed industrial gases from a source or storage cylinder pressure of not more than 5500 psig (37.91 MPa) to the use pressure.
1.2 Regulators covered by these requirements are intended for use with compressed gases such as air, carbon dioxide, inert gases, fuel gases, nitrogen, nitrogen oxide, and oxygen.
1.3 Regulators for welding, cutting, and heating operations are intended for use in accordance with the
Standard for the Design and Installation of Oxygen-Fuel Gas Systems for Welding, Cutting, and Allied
Processes, NFPA 51.
1.4 These requirements do not cover:
a) LP-Gas pressure regulators for equipment intended for installation and use in accordance with requirements of the Liquefied Petroleum Gas Code, NFPA 58. Such regulators are evaluated under the Standard for LP-Gas Regulators, UL 144.
b) Regulators for handling liquids under cryogenic temperatures.
c) The regulating performance flow characteristics of the regulator, and the physiological effects of regulators to be used with medical gases.
2 Components
2.1 Except as indicated in 2.2, a component of a product covered by this standard shall comply with the requirements for that component. See Appendix A for a list of standards covering components used in the products covered by this standard.
2.2 A component is not required to comply with a specific requirement that:
a) Involves a feature or characteristic not required in the application of the component in the product covered by this standard, or
b) Is superseded by a requirement in this standard.
2.3 A component shall be used in accordance with its rating established for the intended conditions of use.
2.4 Specific components are incomplete in construction features or restricted in performance capabilities. Such components are intended for use only under limited conditions, such as certain temperatures not exceeding specified limits, and shall be used only under those specific conditions.UL 252 pdf download.