What causes carbon monoxide in a home?

Any fuel-burning appliance can produce CO: furnaces, water heaters, gas stoves, fireplaces, wood stoves, and portable generators. CO buildup occurs when these appliances malfunction, are improperly vented, or are used in enclosed spaces. The CPSC reports that portable generators and heating equipment are responsible for the majority of residential CO deaths.

Can you smell carbon monoxide?

No. Carbon monoxide is completely odorless, colorless, and tasteless. You cannot detect it with your senses. This is why the CDC calls it the silent killer and why working CO detectors are the only reliable way to know if CO is present in your home. Never rely on smell to determine if your home is safe.

How many CO detectors do I need?

The CPSC recommends at least one CO detector on every level of your home and one outside each sleeping area. For maximum protection, place one inside each bedroom as well. Choose detectors with battery backup so they continue working during power outages, which is when generator-related CO risk is highest.

What is the difference between a CO alarm chirp and a real alarm?

Most CO detectors use a continuous alarm pattern (four beeps, pause, four beeps) to indicate detected carbon monoxide. A single chirp every 30 to 60 seconds typically means low battery or end-of-life. Check your detector's manual for its specific patterns. Treat any continuous alarm as a real emergency.

Emergency Response

Carbon Monoxide Poisoning: What to Do

If you're in this situation right now

If your carbon monoxide alarm sounds, get everyone outside immediately and call 911. Do not re-enter the home. CO is colorless and odorless, making detectors your only reliable warning. According to the CDC, carbon monoxide poisoning kills more than 400 Americans each year, and thousands more are hospitalized. Symptoms mimic the flu: headache, dizziness, nausea, and confusion.

Updated March 2026 · Reviewed March 2026

Recognize the Symptoms

Carbon monoxide is called the silent killer because you cannot see, smell, or taste it. Symptoms build gradually and are easy to dismiss as a cold or flu, especially in winter when CO incidents peak and flu is common.

Early exposure: Dull headache, weakness, dizziness, nausea, shortness of breath.
Increasing exposure: Confusion, blurred vision, vomiting, loss of coordination.
Severe exposure: Loss of consciousness, seizures, death.
Key clue: If multiple household members (including pets) develop similar symptoms at the same time, suspect CO immediately.

Sleeping Victims Never Wake Up

According to the CDC, people who are sleeping or intoxicated can die from CO poisoning before ever experiencing symptoms. This is why working CO detectors are non-negotiable in every home, especially near sleeping areas.

If Your CO Alarm Goes Off

When your carbon monoxide detector sounds, treat it as a real emergency every single time. The CPSC is clear: never assume it is a false alarm or a low battery chirp. Know the difference: most detectors use a continuous pattern for CO and a single chirp for low battery.

1Get everyone out immediately. Do not stop to open windows, investigate, or gather belongings. Move to fresh air outside.
2Count heads. Account for every person and pet in the household.
3Call 911 from outside. Tell the dispatcher your CO alarm is sounding. Do not call from inside the home.
4Do not re-enter the home until emergency responders have tested the air and confirmed it is safe. CO can remain at dangerous levels even after ventilation.

If Anyone Has Symptoms

Tell the 911 dispatcher immediately if anyone is experiencing headache, dizziness, nausea, or confusion. CO poisoning requires medical treatment. First responders will administer oxygen, and severe cases may need hyperbaric oxygen therapy. Early treatment prevents permanent brain and organ damage.

Test Your Response

It is a cold January night. You wake up with a pounding headache and notice your spouse also feels nauseous. Your CO detector is chirping with a steady alarm pattern, not the single low-battery chirp.

What do you do first?

Choose your answer

Be honest. No one's watching.

Prevention

Every CO death in a home is preventable. The two lines of defense are properly maintained fuel-burning appliances and working CO detectors. The CPSC reports that the majority of CO incidents involve heating equipment, generators, or vehicles running in attached garages.

1Install CO detectors on every level of your home and outside each sleeping area. Replace them every 5 to 7 years per manufacturer instructions.
2Schedule annual inspections of your furnace, water heater, fireplace, and any fuel-burning appliances by a qualified technician.
3Never run generators indoors. Place portable generators at least 20 feet from any window, door, or vent. This includes garages, basements, and enclosed porches.
4Never warm up a car in an attached garage, even with the garage door open. CO accumulates quickly in enclosed spaces.

Detector Placement

Mount CO detectors at breathing height (about 5 feet up on the wall) or on a nightstand near beds. Unlike natural gas detectors, CO mixes evenly with air and does not rise or sink, so breathing-height placement gives the most accurate reading. Test detectors monthly.

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Carbon Monoxide Poisoning: What to Do

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If Your CO Alarm Goes Off

Prevention

Frequently Asked Questions

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