"Christian McArdle" wrote in message
...
It can reduce the amount of natural parasitic ventilation below a safe
level for an open flued appliance.

Can we have that in English, please?

You might be still alive because the room is getting air through holes in
the cavity wall (probably below floor level). When you fill the cavity
wall
with foam, those holes will be blocked, the air won't get to the fire and
you will die a slow and lingering death.

The cavity is filled with fibrous rockwool which is blown in, not a solid
mass which bungs up every hole!

Mary

Christian.