This part of ISO 23551 specifies safety, constructional and performance requirements of valve-proving systems, hereafter referred to as VPS, intended for use with gas burners and gas-burning appliances. It also describes the test procedures for checking compliance with these requirements and provides information necessary for the purchaser and user. This part of ISO 23551 applies to all types of VPS which are used for the automatic detection of leakage in a gas burner section having at least two valves designed in accordance with ISO 23551-1 and which give a signal if the leakage of one of the valves exceeds the detection limit. This part of ISO 23551 applies to VPSs with a declared maximum working pressure up to and including 500 kPa for use in systems using fuel gases. This part of ISO 23551 does not apply to VPSs for use in explosive atmospheres.