Carbon monoxide alarm going off: what to do
Carbon monoxide (CO) is a poisonous gas you can't see or smell. High levels can kill within minutes. If the alarm goes off, treat it as real, even if nobody feels sick.
When the CO alarm sounds
- Get everyone outside to fresh air right away, pets too.
- Call 911 from outside.
- Don't go back in until the fire department says it's safe.
Feeling fine is not a reason to stay.
Where CO comes from
CO can come from furnaces, gas stoves, fireplaces, grills, generators and cars. More than 200 people in the United States die every year from accidental CO poisoning linked to consumer products that aren't on fire.
How to prevent it
- Never run a generator, a charcoal grill or a camp stove inside your home, a garage or a basement, even with the doors or windows open.
- Run generators outside only, at least 20 feet from the home, with the exhaust pointed away.
- Test CO alarms once a month. Alarms belong on every level of the home and outside sleeping areas.
- If there's no CO alarm and the home has gas appliances, a fireplace or an attached garage, ask your landlord about one.
Rent your home? Get the free move-in safety checklist. Own or manage rentals? SaferResident gives every tenant a 20 minute course on this, built around your building.
Sources
- Carbon Monoxide Poisoning Basics, Centers for Disease Control and Prevention (CDC)
- Prevention Guidelines: You Can Prevent Carbon Monoxide Exposure (2017), Centers for Disease Control and Prevention (CDC), National Center for Environmental Health
- Carbon Monoxide Information Center, U.S. Consumer Product Safety Commission (CPSC)
- Carbon Monoxide safety, National Fire Protection Association (NFPA)
- Keep Warm and Safe This Winter: Tips for Using Generators, Furnaces and Space Heaters, U.S. Consumer Product Safety Commission (CPSC)
Updated October 1, 2026. General safety information. It doesn't replace your building's safety systems, local codes or your lease. In an emergency, call 911.