Quick AnswerChimney fires are almost always fueled by built-up creosote igniting inside the flue. If you see flames, dense smoke, or hear a roaring noise from the chimney right now, call 911 immediately. If you suspect one already happened, don’t use the fireplace again until a professionally trained technician completes a Level 2 inspection.
Likely Causes
- Creosote buildup igniting inside the flue — this flammable residue accumulates from past fires and ignites once it gets hot enough.
- Loud cracking or popping sounds from the chimney — a common sign a fire is actively burning inside the flue right now.
- A roaring, freight-train-like noise — rapidly burning creosote generates intense heat and draft inside the chimney.
- Dense black smoke or flames from the chimney top — visible from outside, this confirms an active chimney fire.
- Warped metal parts or damaged roofing near the chimney — evidence a fire already burned hot enough to deform metal or scorch shingles, even if no one noticed.
- Cracked, discolored flue tiles or puffy, honeycombed creosote — signs a technician finds during inspection that reveal a past fire nobody caught.
How Urgent Is This?
A chimney fire is a high-urgency safety event, active or not. A fire in progress can spread heat and sparks into the surrounding structure within minutes, and even a small, quickly contained fire can crack flue tiles or warp the liner in ways you can’t see from inside the house. Those hidden cracks create a path for extreme heat and sparks to reach nearby wood framing the next time you build a fire, which is why every suspected chimney fire — big or small — is treated as urgent.
What to Do Right Now
- If a fire is actively happening, call 911 immediately — don’t wait to see if it burns itself out
- Evacuate the house, and close the damper only if you can reach it safely to help cut off oxygen
- Never pour water on an active chimney fire — the sudden thermal shock can crack the flue tiles
- Schedule a Level 2 inspection before using the fireplace again — required after any suspected chimney fire, even a small one
FAQs
Yes. Standard chimney safety practice calls for a Level 2 inspection after any chimney fire, no matter how small or quickly it was contained. Even a brief fire can crack flue tiles or warp metal components in ways that aren’t visible from the firebox.
Unnoticed chimney fires often leave behind warped metal chimney parts, cracked or discolored flue tiles, scorched roofing material near the chimney, or creosote that looks puffy and honeycombed instead of flat and glossy. A technician can spot these signs during an inspection even if you never heard or saw anything unusual.
Not until a professionally trained technician completes a Level 2 inspection and confirms the flue is structurally sound. Using the fireplace again before that check risks directing heat and sparks through a damaged liner and into nearby combustible framing.