Today’s invention is inspired by a question in New Scientist (you will probably need a subscription to read this).
It seems that reams of paper don’t burn primarily because the paper is treated with “rutile titanium dioxide, one of the most fire-resistant substances known”.
So imagine fire doors which are made hollow, but with postal slots in their surfaces. This would allow spare paper to be stored, as blocks, conveniently until needed.
It would also allow paper waiting to be shredded to be kept in a secure place, inside firedoors, whilst actually doing something useful.