Call insurance co. I had a fire place back up for just a few seconds, much less than half a minute. My daughter lite a fire using a wax fake log, actually two of them. the damper was open. a cold chimney with no draft. she smoked the house like you wouldn't believe. a two man cleaning crew was here for 2+ weeks. then I had to repaint the entire house.(really not finished painting and it has been 2 1/2 years) what a mess.
My brother in law had an incidence where the heat exchanger failed on an oil fired furnace. ins clean and paint. oil co replaced exchanger things ok for a while. happened again. upon inspection exchanger was installed wrong. start the process all over again. clean paint and ins co dropped them after the second time.
get the furnace inspected yesterday if not sooner !!!!
bernie