This International Standard defines the construction, safety and performance requirements of packaged or factory matched hydrogen gas generation appliances, herein referred to as hydrogen generators, using electrochemical reactions to electrolyse water to produce hydrogen and oxygen gas. This International Standard is applicable to hydrogen generators that use the following types of ion transport medium: — Group of aqueous bases; — Solid polymeric materials with acidic function group additions such as acid proton exchange membrane (PEM). This part of ISO 22734 is applicable to hydrogen generators intended for indoor and outdoor commercial and industrial use (non-residential use). Hydrogen generators that can also be used to generate electricity such as reversible fuel cells are excluded from the scope of this International Standard. This International Standard is intended to be used for certification purposes.