Carbon monoxide alarm beeping? What each beep means and what to do now

You can't see, smell or taste carbon monoxide (CO), and it can poison you before you notice (VdF NRW). That's why the alarm uses different sounds for "danger" and "I need attention". This guide shows how to tell them apart.

If the alarm is sounding

1. Treat it as real and don't look for the cause.

   

   CPSC says never to ignore a CO alarm that is sounding, and not to try to find the source. Searching the house keeps you breathing the gas for longer.

   Don't assume it's a false alarm because nobody feels ill. CO can poison people without them feeling short of breath (VdF NRW).

2. Careful: only do this if it takes a few seconds on your way out. Getting out comes first.

   On your way out, switch off a fuel-burning appliance and open a door or window.

   

   The NHS says to stop using the appliance you suspect, such as a boiler, cooker or heater, if you can. FireAngel adds opening doors and windows as you leave.

   If you have gas appliances and smell gas, don't switch lights or other electrics on or off, and don't strike a match (Rescue 1122).

3. Get everyone out, then count heads.

   

   Move to fresh air outside and make sure everyone in the home is with you (CPSC, NFPA). Help children, older people and anyone else who needs it.

   Don't put yourself in danger to rescue someone. Tell the emergency services where they are (VdF NRW).

   You should see: everyone who was inside standing with you in the open air.

4. Call for help from outside.

   

   Who to call depends on your country:

   • UK: the National Gas Helpline on 0800 111 999 if a gas appliance may be the cause, and 999 if anyone has trouble breathing, sudden confusion or passes out (NHS).
   • Germany: 112. Say that you suspect carbon monoxide and describe any symptoms (VdF NRW).
   • US: 911 or the fire department (CPSC).
   • Pakistan: Rescue 1122 (Rescue 1122).

5. Watch for symptoms and get medical advice.

   

   The NHS lists headache, dizziness, feeling or being sick, weakness, tiredness and confusion, chest and muscle pain, and shortness of breath. Symptoms often ease once you're out in fresh air, so feeling better doesn't mean you're fine.

   In the UK, call 111 for urgent advice, or 999 for severe symptoms. Don't drive yourself to A&E (NHS). In Germany, call 112 (VdF NRW).

6. Stay out until you're told it's safe, then get the appliance checked.

   

   Don't go back in until the emergency services say it's safe (CPSC, NFPA). Don't use the appliance again until a qualified engineer has checked it.

   If the alarm goes off again within 24 hours of going back in, repeat these steps and have a qualified technician inspect all your fuel-burning equipment (CPSC).

Find out why it's chirping

1. Count the beeps, time the gap and watch the light.

   

   On most alarms, four beeps in a row means carbon monoxide and three means smoke or fire (NFPA). A single chirp every 30 or 60 seconds usually means the battery is low (NFPA).

   Count two or three rounds, and time the gap with your phone's clock.

   You should see: a pattern that repeats, such as one chirp a minute, or 3 quick beeps a minute.

2. Find the model and the replace-by date on the back.

   

   FireAngel prints a replace-by date on the back of every alarm. Beep patterns differ between makers and even between models, so the model name tells you which row of the table below applies.

   If the alarm has a screen, check it too. On Kidde alarms with a display, "Lb" means low battery, and any number shown should be treated as CO: leave and call for help.

3. Match the pattern to your brand.

   

   Brand	Carbon monoxide	Low battery	End of life	Fault
   Kidde	4 short beeps, 5 seconds' silence, repeat	1 chirp every 60 seconds	1 chirp every 30 seconds, from 7 years after first power-up	1 chirp every 30 seconds can also mean a fault; continuous squeal can mean it's unplugged
   FireAngel	4 loud beeps, repeating	1 beep and 1 flash every 40-60 seconds	3 rapid beeps and 3 flashes every 40-60 seconds	2 rapid beeps and 2 flashes every 40-60 seconds
   First Alert	4 beeps, then a pause	1 beep every minute	5 beeps every minute	See the manual
   Any brand (NFPA)	4 loud beeps, repeating	1 chirp every 30 or 60 seconds	Varies by maker; chirping that continues after a new battery	See the manual

   The patterns come from each maker's support page. Older models can behave differently, so the manual for your model has the final say (FireAngel, First Alert).

4. Low battery: change the batteries, or the whole alarm if they're sealed.

   

   If the batteries can be changed, fit new ones (Kidde, FireAngel). Plug-in alarms with a backup battery need it changed too (First Alert).

   A sealed-for-life alarm can't take new batteries. FireAngel says to replace the whole alarm within 30 days of the low-battery warning. Some FireAngel models let you silence the chirp for 8 hours, up to 10 times, while you get a new one.

   You should see: the chirping stops, and the normal light flashes again.

5. End of life or fault: replace the alarm.

   

   The sensor wears out and can't be reset. When the end-of-life signal starts, replace the alarm (FireAngel, NFPA). Kidde says an alarm at end of life can no longer detect CO.

   If it chirps for a fault, FireAngel says to replace it straight away and contact them if it's still under warranty. Kidde's US support line is 1-800-880-6788.

6. One beep a minute after an alarm? CO was found while you were out.

   

   Some FireAngel alarms have an alarm memory: a regular beep every 40-60 seconds, with a light that double-flashes or stays on, shows CO was detected recently, possibly while you were away. The memory lasts 48 hours to 7 days, depending on the model (FireAngel).

   Treat it as a warning. Keep the appliance switched off and have it checked before you use it again. Keep the alarm's manual so you know what your model's memory signal looks like.

Keep your alarm working and in the right place

1. Test it once a month with the test button.

   

   NFPA says to test CO alarms at least once a month and to replace any that don't respond. The button only checks the electronics, not whether the sensor still works (CPSC), so still replace it by its date.

   Brand-new sealed alarm stays silent? Check you removed the isolation pin before testing (FireAngel).

   You should see: the alarm sounds while you press the button, then goes quiet.

2. Put alarms near where people sleep, and on every level.

   

   NFPA says to put CO alarms in or outside every sleeping area and on every level, ideally linked so that when one sounds, they all sound. If you only have one, VdF NRW says to put it in or just outside the bedroom, 1.5 to 1.85 m above the floor.

   Keep alarms out of kitchens and away from spots right above fuel-burning appliances, heating vents, or curtains and furniture that could cover them (CPSC, VdF NRW). Your alarm's manual has the final word on placement (NFPA).

Rules in the UK, Germany, the US and Pakistan

If it doesn't work

Put spare batteries and a torch in your home emergency kit so a chirp at night is a quick fix.