Fuel Cell Questions

Yes, fuel vapor could be a problem. Boats have a big problem with fuel vapor in the bilge/engine area, this is why they have blowers to exhaust the fumes before you crank the motor. The reason that the fumes build up in a boat is because the bottom of the bilge is air tight, if it wasn't the boat would sink.

Fuel vapors will always find the lowest spot (they are heavier than air) so if you have an opening in the lowest spots of the trunk, like the spare tire well, the vapors will go out that opening and won't build up.

The cell, cap and lines themself will be air tight when closed. The only time you will get some vapor is just during filling. But not enough to worry about if you have enough ventilation.

Chuck