Most chimney problems can wait for a scheduled visit. The six below cannot. Each section tells you how to recognise it, exactly what to do in the first few minutes, and why it has to be dealt with before the fireplace is used again.
1. Chimney fire
A chimney fire is creosote — the tar left behind by wood smoke — igniting inside the flue. It can roar like a jet, or it can burn slowly and silently and still crack the liner.
Warning signs: a loud cracking or a deep rumbling like a freight train, dense smoke, a strong hot or acrid smell, flames or glowing chunks shooting out of the top, or a flue that is visibly glowing or vibrating.
What to do right now:
- Get everyone and every pet out of the house.
- Call 911 from outside.
- If you can reach it safely in seconds, close the glass doors or the fresh-air intake to starve the fire of oxygen, and set off a chimney fire extinguisher (chimney flare) if you own one.
- Do not throw water into the firebox — the steam and thermal shock can crack the masonry.
- Stay out until the fire department says it is clear.
A fire that seems to burn itself out in minutes is still an emergency: the heat can reach well over a thousand degrees and crack the flue tiles, so the next ordinary fire can send flames straight into the framing. NFPA 211 requires a Level 2 inspection after any chimney fire before you light another, and a cracked flue almost always needs relining.
2. Carbon monoxide leak
Carbon monoxide is a colourless, odourless gas produced by burning wood, gas or oil. A blocked or leaking flue lets it collect indoors instead of venting out. It is the one on this list you cannot see, smell or hear coming.
Warning signs: a CO alarm sounding; headaches, dizziness, nausea or drowsiness that ease when you leave the house and return when you come back; a gas flame burning yellow instead of crisp blue; soot streaks around the appliance; or heavy condensation on nearby windows.
What to do right now:
- Get everyone and pets outside into fresh air immediately — do not stop to open windows or find the source.
- Call 911 or the fire department from outside.
- Seek medical help for anyone with symptoms, and tell them you suspect carbon monoxide.
- Do not go back inside or restart the appliance until the fire department and a technician have cleared it.
Once it is safe, the flue and the appliance both have to be checked before anything is relit. A gas fireplace that is sooting or burning yellow is a common culprit, and so is a flue that has quietly blocked.
3. Severe flue blockage
When a flue is packed with creosote, a fallen tile, leaves, or an animal nest, combustion gases have nowhere to go and push back into the room. A full blockage turns every fire into a carbon-monoxide risk.
Warning signs: smoke filling the room as soon as you light a fire, a fire that will not catch or stay lit, a strong smoky smell with no fire, soot puffing back into the room, or scratching and rustling sounds from the flue.
What to do right now:
- Put the fire out and stop using the fireplace or appliance.
- Open windows and doors to clear the smoke, and move anyone affected into fresh air.
- Check that your CO alarms are working.
- Leave the flue alone — do not try to force the blockage down into the firebox.
A sweep clears the flue and finds what caused the blockage; if a cap is missing, a new cap keeps animals and debris out for good.
4. Smoke backdrafting
Backdrafting is when the air pressure in your house pulls smoke and exhaust back down the chimney instead of letting it rise. A tight, well-sealed home with powerful exhaust fans is the classic setup for it.
Warning signs: smoke rolling out of the firebox into the room, a cold draft pouring down the chimney, the smell of old smoke or exhaust indoors, or smoke that starts backing up the moment a kitchen or bathroom fan or the furnace kicks on.
What to do right now:
- Crack a window near the fireplace to give the fire the air it needs.
- Turn off kitchen and bathroom exhaust fans and any whole-house fan that is competing for air.
- Stop adding fuel and let the fire die down rather than fighting the draft.
- Ventilate the room until the smoke clears.
Backdrafting has several causes — a short or cold flue, a missing cap, or house pressure — so it is worth an inspection to pin down which one, rather than guessing.
5. Sudden structural damage
Masonry fails suddenly after a lightning strike, a severe storm, or years of water damage finally giving way. A leaning or crumbling chimney is both a falling-brick hazard and an open path for fire and gases.
Warning signs: bricks or large pieces of the crown on the roof or the ground, a chimney that visibly leans or has pulled away from the house, wide cracks running through the masonry, or a sudden pile of tile and debris in the firebox.
What to do right now:
- Stop using the fireplace at once.
- Keep people and vehicles away from the area below and around the chimney.
- If any part is actively falling, or the chimney was struck by lightning, call 911.
- Do not climb on the roof to inspect or tarp it yourself.
Once it is stable, an inspection sorts out whether it needs targeted repair or a rebuild — and in a lot of cases a repair package is enough, as our alternatives to a rebuild guide explains.
6. Dryer vent fire
It is not the chimney, but it is the same kind of emergency and we handle it: lint trapped in a dryer vent is highly flammable, and a clogged vent lets it overheat and ignite.
Warning signs: a burning smell while the dryer runs, a dryer that is hot to the touch, clothes that take several cycles to dry, or a dryer that keeps shutting itself off.
What to do right now:
- Stop the dryer and turn it off at the wall; if it is gas, shut off the gas.
- If you see or smell fire, get out and call 911 — do not open the dryer door, which feeds the fire air.
- Do not run the dryer again until the vent has been cleared.
A blocked vent is the cause nearly every time, which is why dryer vent cleaning is a safety job, not a convenience.
When to call us, and how fast we come
Once anyone in danger is safe and the fire department has done its part, call Ace Chimney Service at (815) 320-0883. We are based in Crystal Lake and cover McHenry County seven days a week, 7am to 7pm, and we will tell you honestly how quickly we can get to you and what the first step is. If you are not sure whether what you are seeing is an emergency, our guide to chimney warning signs helps you tell.
Frequently Asked Questions
What counts as a chimney emergency?
Anything that puts your home at immediate risk of fire or carbon monoxide: an active chimney fire, a sounding CO alarm, a fully blocked flue, smoke backing into the house, or masonry that is falling or leaning. If people need to leave the house, it is an emergency.
How quickly can you come out for an emergency?
Call us and we will tell you honestly how soon we can be there. We cover Crystal Lake and McHenry County seven days a week. For anything involving active fire or carbon monoxide, call 911 first and get everyone outside.
My carbon monoxide alarm went off. What do I do?
Get everyone and pets outside into fresh air right away, then call 911 from outside. Do not reopen windows and hunt for the source, and do not go back in or restart the appliance until the fire department and a technician have cleared it.
Can I use my fireplace after a small chimney fire?
No. Even a brief chimney fire can crack the flue liner, so the next ordinary fire can reach the framing. NFPA 211 requires a Level 2 inspection after any chimney fire before the fireplace is used again.
Smoke is pouring into the room. Is that urgent?
Yes. Put the fire out, ventilate the room, move anyone affected into fresh air, and check your CO alarms. It usually means the flue is blocked or the chimney is backdrafting, and both need to be sorted before the next fire.
A piece of my chimney fell off. Is that an emergency?
Treat it as one. Stop using the fireplace, keep people clear of the area, and if masonry is still falling or lightning was involved, call 911. Falling brick is dangerous and a breached chimney can let fire and gases into the house.
Do you work evenings and weekends?
We are open seven days a week, 7am to 7pm, weekends included. That covers the cold snaps when everyone lights the fireplace at once and problems tend to show up.
What does emergency chimney service cost?
It depends on what is found once it is safe to assess. We quote before any work begins, and our everyday starting prices are on the pricing page so there are no surprises. See the pricing page.
Written by Johnathan Mason, owner of Ace Chimney Service, Crystal Lake, IL — 29 years in chimney and fireplace work.
Published: October 18, 2026 · Updated: October 18, 2026
Chimney or fireplace emergency in Crystal Lake or McHenry County? Once everyone is safe, call Ace Chimney Service at (815) 320-0883. Open 7 days a week, 7am to 7pm.