Why is my carbon monoxide detector going off when my fireplace is running?
Treat it as real every time: get everyone outside, then call 911 and let the fire department meter the air. Once the house is cleared, the usual culprits we find are a blocked vent or chimney, a failed glass gasket, vented logs running with the damper partly closed, a dirty burner, or a tight house backdrafting exhaust when kitchen and bath fans are running. Don't relight until it's diagnosed.
Before anything else
A CO alarm sounding while the fire is burning is the one scenario the device exists for — never write it off as a false alarm, pull the battery, and carry on. Shut the fireplace down if you can do it on the way out, open a door or window, and get people and pets into fresh air. The fire department will tell you what the actual levels are; low readings still mean the fireplace stays off until someone finds the source. Alarms do fail with age — most expire after seven to ten years — but you confirm that after the house is metered, not before.
What we usually find when we get there
The same handful of problems accounts for most of these calls. Burners and pilot assemblies clogged with a summer's worth of dust and spider webs — the classic WNC off-season failure — burn rich and dirty. Vent terminations and chimneys get blocked by nests, leaves, or debris, so exhaust backs up the way it came. On direct-vent units, an aged gasket or an unlatched glass panel breaks the seal that's supposed to keep combustion out of the room. On vented log sets, a damper that has crept partway closed spills exhaust at the lintel. And units running the wrong orifices for their fuel — a real issue where propane serves Fairview, Candler, and Brevard homes — make CO they were never designed to make.
The tight-house backdraft problem
Newer, well-sealed mountain homes add a subtler cause: negative pressure. Run a big range hood, a couple of bath fans, and a clothes dryer at once in a tight house, and that air has to come from somewhere — sometimes it comes down the chimney, dragging exhaust with it. Open-flue fireplaces and B-vent units are the vulnerable ones; sealed direct-vent fireplaces largely shrug it off, which is one more reason they're our default in new construction. Whatever the cause turns out to be, we quote the fix upfront and most are handled in a single visit. Call (828) 545-0525 — no-heat and safety calls come first.
How we can help
Related questions
- Can a blocked chimney or flue push carbon monoxide back into the house?
- How can I tell if my gas fireplace is leaking carbon monoxide?
- What are the symptoms of carbon monoxide poisoning from a fireplace?
- Can snow or debris blocking the outside vent make a gas fireplace dangerous?
- Where should a carbon monoxide detector go in a room with a gas fireplace?
- Can a gas fireplace cause carbon monoxide poisoning?
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