This part of ISO12619 specifies tests and requirements for the excess flow valve, a Compressed Gaseous Hydrogen (CGH2) and Hydrogen/Natural Gas blends fuel system component intended for use on the types of motor vehicles defined in ISO3833. It is applicable to vehicles using Compressed Gaseous Hydrogen (CGH2) in accordance with ISO14687‑1 or ISO14687‑2 and Hydrogen/Natural Gas blends using natural gas in accordance with ISO15403‑1 and ISO/TR15403‑2. It is not applicable to the following: liquefied hydrogen (LH2) fuel system components; fuel containers; stationary gas engines; container mounting hardware; electronic fuel management; refuelling receptacles. NOTE1 It is recognized that miscellaneous components not specifically covered herein can be examined to meet the criteria of this Standard and tested according to the appropriate functional tests. NOTE2 All references to pressure in this Standard are to be considered gauge pressures unless otherwise specified. NOTE3 This Standard may not apply to fuel cell vehicles in compliance with international Regulations.