Only had a chimney fire ONE time and that was way back when I lived in NE Ohio and we heated our farmhouse with an ancient Iron Fireman cast iron furnace converted to gas and I removed the gas burner and with careful scrounging (salvage yards and assoiates) which was before the Internet forums like Farcebook, Criaigslist, and other online sites, I found all the parts to take it back to the original design, including the shaker grates, the shaker handle, the upper grates and the ash box and being not very financially flush back then, our only meat was the deer I killed and dressed during deer season and there were plenty to choose from (and I presume still is back there). I did all my own dressing out and wrapping and freezing too. Even the dog ate deer all winter and by spring, we were all sick if it. You can only make deer so many ways and by spring, deer chili was the was the main course with numerous farts from the kidney beans included, anyways. Be4ing somewhat poor I would fire the furnace primarily with Anthracite coal, the local elevator would deliver coal by the small dump truck load and we had a coal chute that went into the basement and I built a coal bin around the end, but it also got wood dumped in as well as chunks of old rail road ties (roasted them at night when no one could see the smoke or where the stink was coming from
Anyway, I was lax about cleaning the chimney and about late winter it caught on fire. Was a brick chimney with a full fired clay liner and I'm glad it was because the chimney looked like an upside down rocket ship and was spewing hot stuff on the roof and I had to get out the garden hose and keep the roof wetted down so the roof didn't catch on fire, It had some snow on it, thank goodness for that or we would have been homeless. Anyway it burned the chimney clean and I a huge pile of roasted creosote in the cleanout door on the bottom of the chimney. needless to say, I kept up on cleaning it from then until we sold the place and moved up here to Michigan to this farm.
I don't get any chimney fires with either of my biomass stives, just some fly ash wiuch I clean out every spring with the shop vac and a long hose. Nice thing about biomass is no creosote, even with restricted draft. The stoves decide how much induced draft they make, I don't and it's an overfire draft plus an under fire draft, much like how a Scothchback steam boiler operates but no boiler, just a heat exchanger. You have the underfire initiating the combustion and the overfire providing the secondary gasification and combusting any soot or creosote produced. That way, nothing goes up the venting but excess heat that escapes the heat exchanger and a bit of fly ash that collects in the venting and the venting (which is outside, has a cleanout at the very bottom that is removable so I can clean the entire vent from the deck. They average 85% efficiency and emit very little particulates (smoke) except on a cold start, Once running, no visible particulates, just the smell of wood burning and some heat waves. Downside is processed wood pellets aren't cheap today, but I supplement my pellets with free off grade seed corn so it's still a pretty cheap date for us and both my bio-mass stoves are multi fuel capable, that is, I cannot only burn wood pellets but I can combust any domestically grown grain except oilseeds like soybeans because they burn way too hot and the onboard combustion computer cannot compensate for that.