As of late September 2026, the AC in my Riverside ranch house is still running most afternoons, and the fireplace in the living room hasn’t seen a log since last winter. For years the damper just stayed open. No fire, no smoke, no reason to touch the lever. An open flue over an empty firebox looked like nothing at all, and I’d bet plenty of us here in California leave it the same way.
The Riverside County Fire Department’s carbon monoxide page has a line about flues that I used to read as the whole rule: “Open flues when fireplaces are in use.” That line is about a fire that’s burning. It doesn’t say to leave the flue open when nothing is.
Have an HVAC pro check the damper seal.You describe checking the damper’s seal and fit, or sealing an unused flue, and local HVAC pros call about your request.“My fireplace damper seems to leak air year-round.”→Free for homeowners · Your number stays private
What the Department of Energy says
The U.S. Department of Energy’s Energy Saver tips are blunt about the other half: “Keep the fireplace damper closed unless a fire is burning. Keeping the damper open is like keeping a window wide open during the winter; it allows warm air to go right up the chimney.”…