Originally Posted by
jackal
Is the floor even airtight? I would expect not.
No. It would be dangerous if it were. If there is a rapid depressurization the pressure above and below the floor must equalize fast enough to prevent structural damage. There are panels in the floor designed to allow this rapid pressure equalization. The cargo areas do get quite cold, though, as they typically do not have much, if any, heated air directed into them.