Very well thought out response to friendly & hostile fire.
In Texas which has always had a lot of open gas heaters, that is the type that is connect to the shut off valve coming out of the wall or floor without any type chimney, this was the standard 163 line policy (NY163 line) exclusion. SPECIFIC COVERAGE CONDITIONS
Conditions Applicable only to Smoke:loss by smoke shall be limited to loss caused by a sudden, unusual and faulty operation of any heating, disposal or cooking unit, only when such unit is connected to a chimney by a smoke pipe, and while in or on the premises described herein, excluding, however, smoke from fireplaces or industral apparatus.
Bath rooms use to have a small heater in the wall..( no smoke pipe) .that would smoke up a whole whole house with low pressure on a very cold day.
*** I will scan the old Texas Standard 163 line Fire and Lightning Policy which is three pages. If you read ever line on ever page you will never have a problem reading any fire insurance form...... ever..Homeowners, BOP, CP etc. Please send me a email and I will attached and send back.