However when you use finish using your bath typically you have the fan on
and the bathroom door open right? *So it's drawing the air in the bath PLUS
the air from outside the bath. *Would it be a good rule of thumb to

Be careful if there is also a connection to a chimney in the rooms
from which it draws air! It works against the pressure pushing smoke
up and sucks CO2, CO, dust, and whatever is produced by your heating
into your living room.

I recommend to ask a chimney sweep. In my apartment there is a small
fan blowing air into the chimney. Our chimney sweep told us not to
enlarge it since it might blow smoke and poisonous gas into the other
apartments.

virtuPIC
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