Creosote buildup stat from the NFPA manual caught me off guard

I was flipping through the NFPA 211 handbook last week and saw that only 1/8 inch of creosote is enough to start a chimney fire, which is way thinner than I ever thought.

3 comments

3 Comments

nathanking25d ago

Whoa, that's wild. I actually heard a similar stat from a local firefighter who came to talk at my town's safety fair last fall. He said a lot of folks don't realize how little buildup it takes, something like a quarter inch of that fluffy stuff is basically a pile of kindling waiting to catch. I always thought you'd need a thick crust of that stuff before it was a problem, but apparently that's totally wrong. He showed us a picture of a chimney after a small fire, and the creosote was mostly gone but the flue was cracked and ruined.

paigewood25d ago

@nathanking wait so even after a small fire the chimney is basically ruined? That's wild. Is the flue liner just done for after any creosote fire no matter how small or does it depend on how hot it burned?

reeseanderson2d ago

One angle I haven't seen mentioned is that it's not just the heat from the fire itself that does the damage. It's the rapid cooling after you put it out or let it burn down. That temperature swing can crack terra cotta liners even in a small fire, and nobody talks about that part. Plus, those cracks let carbon monoxide seep into your house instead of going up the chimney, which is way scarier than just needing a repair.