scope:

This part of the standard specifies the safety, construction and performance requirements for gas/air ratio controls for inlet pressure up to and including 500 mbar of nominal connection size up to and including DN 150, intended for use with gas appliances for use with one or more fuel gases of the first, second or third families. It also describes the test procedures for evaluating these requirements and specifies information necessary for installation and use. The standard applies to air/gas ratio controls which function by controlling a gas pressure (or differential pressure) output in response to an air pressure (or differential pressure) and to a furnace back pressure signal input, but gas/air ratio controls which change the air pressure in response to the gas pressure are not excluded.