The boil off gas from a tank of liquid hydrogen can be expected to be extremely pure and clean. In a sense the liquid hydrogen has been distilled. Extended operation of Fuel Cell Electric Vehicles, for example, relies on the need to protect fuel cell membranes and catalysts from contamination. Fuel cell degradation in use can have many causes, but nevertheless fuel purity (in normal conditions and in the case of refuelling equipment failure) can be expected to be a major concern for any system relying on high pressure hydrogen gas handling.
