'Dave , if-when the damper sticks shut you get flue gas in the building,
not up the chimney, Right. A mechanical damper retrofit without saftey
shut off controls ??'

ME: Rans, YEP ! Back in the 1980's during the Energy Crunch,
mechanical flue dampers were very very popular . I personally never had
one that stuck closed . Often, installers would put in draft diverter
spill switches ...but most installers did not.

'I don`t buy your logic, and have never heard of that option offered as
OEM or aftermarket.
=A0=A0Sounds like dangerous advise , post facts.
'

ME: You dont have 'to buy my logic'...cause it isnt '
my logic ; do a google and youll soon find these as an aftermarket
item. All my wholesalers still sell them. In fact, i have about 5 or 6
used ones in my shop -- so, please dont be arrogant by inferring they
dont exist.