Carbon monoxide detector alarm: what to do?

A carbon monoxide (CO) detector alarm is a serious warning. CO is an invisible, odorless gas that can cause sudden illness or death. If your alarm sounds, act immediately: do not ignore it or assume it is a false alarm.

What is happening

Carbon monoxide is produced by fuel-burning appliances such as furnaces, water heaters, stoves, and generators. A detector alarm means CO levels have reached an unsafe threshold. Even if no one feels sick yet, the danger is real.

Emergency warning

If the alarm sounds or anyone has symptoms (headache, dizziness, nausea, confusion, shortness of breath), call your local emergency services immediately from a safe location. Do not wait to see if the alarm stops.

What to do first

1. Evacuate everyone (including pets) to fresh air outside. Do not stop to gather belongings.
2. Call emergency services from outside. If you cannot call, ask a neighbor.
3. Do not re-enter the building until emergency responders or a qualified technician say it is safe.
4. Check on everyone for symptoms. If anyone has symptoms, seek medical attention immediately, even if they seem mild.
5. Air out the building only after everyone is out and responders have arrived. Open doors and windows if it is safe to do so, but only after evacuation.

What NOT to do

• Do not ignore the alarm or press the silence button and go back to sleep.
• Do not try to find the source of the CO before evacuating.
• Do not use any fuel-burning appliance (generator, grill, stove) indoors or in a garage, even with doors open.
• Do not assume it is a false alarm. Only a professional can confirm that.
• Do not re-enter until cleared by authorities.

When to seek professional care

Seek medical attention for anyone with symptoms of CO poisoning: headache, dizziness, weakness, nausea, vomiting, chest pain, confusion, or loss of consciousness. Symptoms can appear gradually and may be mistaken for the flu. If someone is unconscious or not breathing, call emergency services and start CPR if trained.

What to monitor

After evacuation, watch for symptoms in yourself and others. CO poisoning can cause delayed effects. Follow advice from medical professionals and do not return to the building until it has been inspected and cleared.

How to prevent it

• Install CO detectors on every level of your home and near sleeping areas. Test them monthly and replace batteries as recommended.
• Have fuel-burning appliances inspected annually by a qualified technician.
• Never use generators, grills, or camp stoves indoors, in garages, or near windows.
• Ensure chimneys and vents are clear and not blocked.

Your safety is the priority. Evacuate first, call for help, and stay out until professionals confirm it is safe. This is general information and not a substitute for professional medical advice. In an emergency, call your local emergency services.