We've recently moved into a 120 year old house and there are a few
mysteries that I would still like to get to the bottom of.

We have a chimney block that has 6 individual chimneys in it, which is
shared with next door. In our bedroom (actually on the ground floor)
there's an airbrick into a chimney that I thought was disused. That is
until our neighbour's boiler started up and I realise that there is a
flue running up the chimney for next door's boiler.

This wakes us up when it starts up at 5am! I've temporarily taped some
plywood over the vent and it makes a big difference to the noise. Do
you think it's a bad idea to permanently block up this vent? I assume
the chimney is sealed at the top, allowing only the boiler flue to
exit. I think this is the only vent into the chimney, and the only
other place it's possible to vent it would be in the lounge, which is
also undesirable.

Any advice gratefully received.

Thanks,
Dave.