[RKDinOKC]

Yep, in the Cayenne the battery is under the driver's seat. It is in compartment that is sealed from the interior and vented to underneath the car. You have to unbolt the top of battery compartment to open it. It opens like a hatch with the driver's seat on top. There is also a tube that goes from a vent hole on the actual battery to under the car. However, the tube is more for liquic overflow from overcharging or over heating than gases. And battery gases are heavier than air.

The 928 is a hatch back and the battery is in the rear hatch area. It is in a compartment under the spare tire well. The door is sealed and it is vented to under the car. But opens with a plastic lever instead of being bolted down like the Cayenne. Never heard of anyone getting gassed in a 928 from either the battery or exhaust fumes from a poorly sealed rear hatch.

Was also taught to always open a window just a crack for ventilation. Then the issue was you might have an exhaust leak letting exhaust gasses into the passenger area not battery fumes. Seem to remember cars having vents that were always open for this reason thanks to Mr. Ralph Nader. So seems very unlikely for battery fumes becoming a problem.