In article ,
"ARWadsworth" writes:
And if your bathroom door fits snug you will have nothing to replace the
extracted air with.

Reminds me of a small room in the middle of a new school building
which contained just a WC, no windows, but an extractor fan connected
to the light. After a few days of use, the extractor fan 'sucked' a
sheet of plasterboard off the wall. The room was rather too well
sealed, and although the fan might not seem very powerful, even a tiny
pressure difference across an 8'x4' sheet of plasterboard adds up
to quite a force (and I doubt it was fixed very well in the first
place).

--
Andrew Gabriel