What to do if?Reviewed: 2025-12-27~1 min

What to do if your CO alarm goes off during a winter storm when the power is out and a generator is running

Short answer

⚠️Depends / use caution

It depends—treat any CO alarm as real first: get everyone to fresh air immediately, shut off the generator and fuel‑burning heaters, and call emergency services. If it’s only a once‑per‑minute low‑battery chirp with no symptoms and no fuel sources running, replace batteries and re‑assess, but don’t ignore persistent alarm patterns.

Why people ask this

In a winter storm with the power out, people often rely on portable generators or fuel heaters, and a CO alarm can be confusing or scary. Snow can block vents and tailpipes, and high winds can blow exhaust back toward the house, making it hard to know what triggered the alarm. People also worry about evacuating in severe weather, where to go to stay warm, and whether the alarm is just a low‑battery chirp during the outage.

When it might be safe

It’s a single, periodic chirp (e.g., once per minute) indicating low battery, not the continuous or repeating pattern of a CO alarm, and no one has headache, nausea, or confusion.
The generator is already off and has been located 20+ feet downwind from the home (not in a garage, basement, or under an overhang) with the nearest door/window closed, and other fuel appliances are off.
Multiple CO alarms with digital displays show 0 ppm after replacing batteries and ventilating the home for at least 20 minutes, and no one has symptoms.
You confirm snow and ice are cleared from furnace, dryer, and fireplace vents and any vehicle tailpipes, and readings remain 0 ppm on a reliable CO meter.

When it is not safe

Continuing to run a portable generator in a garage, on a porch, or within 20 feet of doors, windows, or vents during the storm.
Using a gas stove/oven, charcoal grill, or unvented space heater indoors to keep warm when the power is out.
Ignoring a continuous or repeating alarm pattern, especially if more than one CO alarm is sounding or people have headache, dizziness, or nausea.
Re‑entering the home before it has been fully ventilated and cleared by responders or a verified 0 ppm reading on a CO meter.
Letting snow accumulate around exhaust vents, chimneys, portable heater exhausts, or vehicle tailpipes, which can force CO back into living areas.

Possible risks

Carbon monoxide poisoning leading to headache, dizziness, confusion, loss of consciousness, or death.
Back‑drafting from snow‑blocked appliance vents or high winds forcing generator exhaust into the home.
Delayed symptoms during cold exposure if you try to "wait it out" indoors with a running generator nearby.
Compounded danger from hypothermia outdoors if evacuation is delayed or poorly planned in severe weather.

Safer alternatives

Shut down the generator, evacuate to fresh air, and call 911; once safe, relocate the generator 20+ feet away, downwind, with exhaust pointed away from the home before restarting.
Ventilate the home by opening doors and leeward windows for at least 20 minutes; clear snow from all exterior vents, chimneys, and any vehicle tailpipes.
Use non‑combustion options for warmth and light: extra layers/blankets, battery‑powered heaters designed for indoor use, and flashlights or lanterns.
If you must warm up in a vehicle, only do so outdoors (never in a garage), ensure the tailpipe is fully cleared of snow/ice, and run the engine intermittently.
Consider going to a neighbor’s house, a community warming center, or a shelter announced by local authorities during the storm.
Install and maintain multiple CO alarms with battery backup and, if possible, a portable CO meter to verify 0 ppm before re‑entry.

Bottom line

During a winter outage with a generator, treat a CO alarm as real: get to fresh air, shut off fuel sources, and call for help. Only consider a benign cause like a low‑battery chirp after you’re safe and have verified 0 ppm and clear vents.