Emergencies & Disasters
Carbon Monoxide Alarm Beeping: What It Means and What to Do
General information only, not professional advice. In an emergency, call 911 and follow local officials. How we use sources
In this guide
If your carbon monoxide alarm is sounding four beeps, a pause, and four more, that is the usual alarm pattern. Get everyone outside now, call 911 from outside, and do not go back in until emergency responders say you can. The same goes if anyone in the home feels unwell. Do not stop to look for the source.
Makers’ patterns differ, and a single chirp is a different signal. Both are covered below.
If it is the alarm pattern: leave and call
The Consumer Product Safety Commission (CPSC) lists the first steps:
Never ignore an alarming CO alarm! It is warning you of a potentially deadly hazard.
If the alarm signal sounds do not try to find the source of the CO:
Immediately move outside to fresh air.
Call your emergency services, fire department, or 911.
After calling 911, do a head count to check that all persons are accounted for. DO NOT reenter the premises until the emergency services responders have given you permission. You could lose consciousness and die if you go in the home.
Source: CPSC, “Carbon Monoxide Fact Sheet” (cpsc.gov), accessed November 2026.
The American Red Cross gives the same order in its own words: everyone leaves right away, pets included, you call 911 once you are outside, and nobody goes back in until responders say it is safe. The National Fire Protection Association (NFPA) says to move to a fresh air location outdoors, make sure everyone in the home is accounted for, call for help from there, and stay until emergency personnel arrive.
You do not need symptoms to leave. The CDC says people who are sleeping, drunk, or under the influence of other substances can die from CO poisoning before they have symptoms. Feeling unwell is another reason to go, not a condition for going. The CDC lists the most common symptoms:
The most common symptoms of CO poisoning are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. CO symptoms are often described as “flu-like.”
Source: CDC, “Carbon Monoxide (CO) Poisoning Basics” (cdc.gov), accessed November 2026.
If you have those symptoms and your alarm is not going off, or you have no alarm, CPSC gives this direction:
If you think you are experiencing any of the symptoms of CO poisoning, get outside to fresh air immediately. Leave the home and call your fire department to report your symptoms from a neighbor’s home.
Source: CPSC, “Carbon Monoxide Fact Sheet” (cpsc.gov), accessed November 2026.
Treatment is a job for responders and doctors, so this page does not cover it.
What the beeps mean
Carbon monoxide alarms make more than one kind of sound, and not every maker uses the same ones. The Red Cross describes a carbon monoxide alarm as four fast beeps and a smoke alarm as three fast beeps. That is a starting point, not a guarantee about your alarm. First Alert’s support page says patterns and lights vary by model and that your model’s manual is the best source. Kidde’s support page points to your product’s user manual for your specific alarm.
| What you hear or see | What it usually means | What to do |
|---|---|---|
| Four beeps, a pause, then four beeps again | The carbon monoxide alarm pattern. Kidde describes four short beeps, five seconds of silence, then four short beeps. The First Alert CO710 manual lists 4 beeps as a CO alarm. | Leave, call 911 from outside, stay out until responders say you can return. |
| A chirp at intervals | Often a low battery or a trouble signal. The interval depends on the maker and model. | Check your label or manual. Replace a low battery. See “If it chirps” below. |
| A chirp that continues after a new battery, or a different chirp count | May mean the alarm is at the end of its life or has a fault. The First Alert CO710 lists 5 chirps for end of life and 3 chirps for a malfunction. Kidde’s support page says its alarm starts chirping every 30 seconds seven years after first power up. | Look up that pattern for your model. Replace the alarm if it is at the end of its life. |
| A number on a digital display (some models), with or without an alert | Kidde says to assume the unit senses carbon monoxide. Kidde also says the numbers that run through the display when you press the test button are not readings. | Treat a number outside a test as carbon monoxide: leave and call 911. |
| One long, continuous squeal | Kidde says this may be a tamper-resist warning (the unit was unplugged or came loose from the outlet) or a malfunction. | Check your model’s manual. |
The named patterns come from Kidde and one First Alert model, so treat them as examples and read your own label or manual. If you cannot tell whether a sound is a chirp or the alarm pattern, leave and call 911. If the label on your alarm is unreadable or you do not know its age, First Alert says replacing it may be the safest option.
If it chirps
First Alert’s support page says a chirp is usually a maintenance or service signal, and in many cases does not mean the alarm is detecting dangerous carbon monoxide. Kidde adds a reason not to ignore one: an alarm in end-of-life mode can no longer detect carbon monoxide, so a chirping alarm may not be protecting you.
Start with the battery, if your alarm has one you can change. NFPA says that if the trouble signal sounds, you check for low batteries and replace the battery if it is low. If the alarm still sounds, NFPA says to call the fire department.
First Alert lists a short set of causes for a chirp after a battery change: the battery may not be seated correctly, the compartment may not be fully closed, the alarm may need a reset, or the alarm may be at the end of its life. It also says reset steps vary by model and that you should follow your model’s instructions.
Some alarms have sealed batteries and nothing to swap. The First Alert CO710 manual describes a sealed, non-replaceable battery and says to install a new alarm after the end of its service life or 10 years, whichever comes first.
The CDC says to replace your CO detector following the manufacturer’s instructions or every 5 years. CPSC says alarms have a recommended replacement age, available from the product literature or the maker, and newer alarms have an end-of-life signal. First Alert says most CO alarms have a manufacture date or replacement information printed on the back or side.
If you need a new alarm, our carbon monoxide detector guide covers what to look for, including battery backup and placement. If the chirp comes from a smoke alarm, see our guide to a smoke detector chirping.
If it stopped, or you think it was a false alarm
CPSC says carbon monoxide alarms are designed to alarm before potentially life-threatening levels are reached, and that currently marketed alarms are not as susceptible to nuisance alarms as earlier models. An alarm that went off and then stopped still went off, so the CPSC steps at the top of this page still apply: get out, call 911, and let the fire department decide. The First Alert CO710 manual notes that carbon monoxide may dissipate by the time an investigator arrives, which can make the source hard to find.
NFPA, citing 2023 National Fire Incident Reporting System data, counts 82,245 CO incidents that needed a local fire department response, and separately 79,286 CO alarm activations where no CO was found. NFPA’s guidance when a CO alarm sounds is still to move to fresh air and call for help.
Pressing the test button does not settle it. CPSC says the test button tests whether the circuitry is operating correctly, not the accuracy of the sensor.
If you were cleared to go back in and the alarm sounds again, CPSC has a specific rule:
If authorities allow you to return to your home, and your alarm reactivates within a 24 hour period, repeat steps 1, 2 and 3 and call a qualified appliance technician to investigate for sources of CO from all fuel burning equipment and appliances, and inspect for proper operation of this equipment.
Source: CPSC, “Carbon Monoxide Fact Sheet” (cpsc.gov), accessed November 2026.
CPSC also says that if the source turns out to be a malfunctioning appliance, you should not operate it until trained personnel have serviced it.
Outages, generators and heaters
The Red Cross says CO poisonings often increase during power outages, as people depend on generators and grills. CPSC puts numbers on it, with the year attached:
In 2020, the highest number of CO deaths associated with any single product category, 92, were associated with generators, which are often used to power homes when the electricity goes out. The second highest number of CO deaths, 33, were associated with portable heaters.
Source: CPSC, “Carbon Monoxide Fact Sheet” (cpsc.gov), accessed November 2026.
The CDC’s generator rules are short and worth reading before the next storm:
Never use a generator inside your home or garage, even if doors and windows are open.
Only use generators outside, more than 20 feet away from any windows, doors, and vents.
When using a generator, use a battery-powered or battery backup CO detector in your home.
Source: CDC, “Carbon Monoxide (CO) Poisoning Basics” (cdc.gov), accessed November 2026.
The same CDC page says never to heat your house with a gas oven. Our space heater safety guide covers portable heaters. For staying warm during an outage, see what to do when the power goes out and how to stay warm without power.
The alarm needs power too. CPSC says hard-wired or plug-in carbon monoxide alarms should have battery backup, and the CDC says to install battery-operated or battery backup detectors near every sleeping area. Without backup, a plug-in alarm depends on the outlet having power. CPSC also says an alarm can provide some added protection but is no substitute for proper use and upkeep of appliances that can produce CO.
Before the next time
- Find the date. Check the label for a manufacture or replace-by date. The CDC’s rule is the maker’s instructions or every 5 years.
- Test and change batteries on schedule. CPSC recommends replacing batteries in smoke and CO alarms annually and testing them monthly. The CDC suggests checking batteries when you change your clocks each spring and fall.
- Put alarms where the agencies say. The U.S. Fire Administration and NFPA both say outside each separate sleeping area and on every level of the home. CPSC does not recommend kitchens or spots above fuel-burning appliances, and says to skip attics and basements unless they include a sleeping area.
- Look up your fire department’s non-emergency number. NFPA suggests calling it ahead of time to learn what number to call if the alarm sounds.
- Agree on an outside meeting place so everyone knows where to stand if the alarm sounds at night. Our family emergency plan covers how to set one.
- Read your own manual once to learn your model’s patterns before the next beep.
If you do not have an alarm yet, our resources page lists a smoke and carbon monoxide alarm item to start with.
Quick answers
What does a carbon monoxide alarm sound like?
The Red Cross describes four fast beeps for a carbon monoxide alarm and three fast beeps for a smoke alarm. Kidde describes four short beeps, five seconds of silence, then four short beeps again. Other models differ, so check your manual.
Can I just silence it?
When the alarm pattern is sounding, the steps CPSC gives are to move outside and call 911, so do that first. Silence and reset features, where an alarm has them, are described in that model’s manual.
Why is it chirping after a new battery?
First Alert lists a battery that is not seated correctly, a compartment that is not closed, an alarm that needs a reset, or an alarm at the end of its life. NFPA says that if it still sounds after you replace a low battery, call the fire department.
How long do carbon monoxide alarms last?
The CDC says to replace them following the manufacturer’s instructions or every 5 years. Makers state their own limits, so check the label or manual for your model.
Follow your local officials
This page draws on what CPSC, the CDC, NFPA, the American Red Cross and the U.S. Fire Administration publish, plus Kidde and First Alert support pages. It does not replace local guidance. Your fire department and emergency management office know your area and your codes, so follow their instructions, and call 911 in an emergency. When in doubt, don’t go back in.
Our family emergency binder has a contacts section and a page for where everyone meets if you get separated, so the fire department’s non-emergency number and your outside meeting spot are written down before the next alarm.
