1.1 Fuels and technologies covered by this part Part 107 covers micro fuel cell power systems, micro fuel cell power units and fuel cartridges using hydrogen produced from water-reactive (UN Division 4.3) compounds as fuel. These systems and units use proton exchange membrane fuel cell technologies. The designs may include fuel processing subsystems to derive hydrogen gas from the water-reactive fuel formulation. This Part 107 only applies to water reactive (UN Division 4.3) solid compounds which solely evolve hydrogen gas upon contact with water (or non-hazardous aqueous solutions). This Part 107 does not include compounds with a subsidiary hazard risk, or which are not permitted to be transported by air according to the ICAO Technical Instructions.