Why not use a direct vent tube to the outside?
Some batteries can be connected directly to a tube that can then pipe the hydrogen directly outside. This approach can be very effective, providing the tubing is properly installed and is never disconnected from the battery. Since there is always a possibility that a battery could become disconnected from its vent tube, either by accident during maintenance, cracks due to aging, or by thermal expansion over time, this solution does not guarantee that hydrogen will never escape into the air inside the shelter causing a disaster.
