ISO 23550:2018 specifies safety, construction, performance and testing requirements for controls for gas burners and gas burning appliances for use with natural gas, manufactured gas or liquefied petroleum gas (LPG). ISO 23550:2018 applies to controls for use at maximum operating pressures up to and including 500 kPa. This document provides the general requirements that are intended to be the basis for the specific control standards found in the ISO 23551 and ISO 23552 series. These include the following:- automatic and semi-automatic gas valves;- gas thermoelectric flame supervision controls;- gas and oil /air ratio controls;- gas pressure regulators;- manual gas valves;- mechanical gas thermostats;- multifunctional gas controls;- air and gas pressure-sensing devices;- gas vent valves;- gas valve-proving systems.ISO 23550:2018 covers type testing only.ISO 23550:2018 is also applicable to Gas Quick Connectors (GQC) for use inside appliances with connections up to, and including DN 25, and a maximum operating pressure up to and including 100 kPa. GQCs include:- tube to tube connections;- tube to control connections; and- tube to fitting connections.ISO 23550:2018 does not apply to mechanical controls for use with liquid fuels. It is also not applicable to corrosive and waste gases.