How do I know if my CO alarm went off because of Carbon Monoxide?

[Guest Co detector]

Either my carbon monoxide or I smoke detector  went off in the middle of the night , but only for a couple minutes. It wasn’t a chirping it was actually going off. The heat was not on. But I flipped the switch to cool air and the alarm stopped. I am afraid to go back to sleep at this point and sitting here googling. Should my son and I get out of the house and call 911? I can’t reach the alarm on the tall ceilings. 

[Rahel Lock]

Good morning
it will be a little late for immediate advice at this point but for future reference it is important to find out if it is your smoke or your co alarm that has gone off. I'd advise to test both units to familiarise yourself with the sound of both units.
Smoke alarms can false alarms if contamination in the smoke chamber (dust, small insects etc) occurs but co alarms normally don't false alarm.

Follow these steps if alarm sounds:
1. Keep calm. Open all doors and windows. Turn off all fuel-burning appliances if possible.
Note: Outdoor conditions could influence domestic CO alarms (bad traffic
pollution in cold weather, for example). In these circumstances, the level of indoor CO might
actually increase when doors and windows are opened.
2. If alarm continues to sound, even after being reset (where appropriate), evacuate the
premises, alerting other occupants to the risk. Leave doors and windows open. Do not re-enter premises.
3. Get medical help for anyone suffering the effects of CO poisoning, and advise that CO inhalation
is suspected.
4. Call Gas Emergency Services: 0800 111 999, or your local Gas Safe Registered Engineer.

[green-foam]

I should point out that the guest (Who posed the question on October 26) is in the USA* so 4 above does not apply.

Another thing to try first is to take the CO alarm down/off the wall and take it outside into fresh air.

If the unit stops then take the unit back inside, if it starts again you do have a CO leak, proceed as above.

If the unit does not stop when out side reset it, and see does it start again.

 

 

 

[Guest Jamie]

My detector when off at around 4am it was very loud but did not stay on.  I’ve stayed and it’s about 45 mins passed it going off and it has t went off again.  Am I ok and what do I need to do tomorrow.  Is detector faulty?

[Guest Vanessa H]

Hello please advise! Carbon monoxide detector alarm sounded at 4am, 4 beeps in quick succession. I know I shouldn’t have but I took the batteries out to stop the alarm. I put them back in and pressed test. The alarm did not sound again but flashed green light to show it’s working. I did not go back to sleep as so scared! It hasn’t sounded since (8 hours later). I have since been out and purchased 2 more alarms (different brands) 1 has a 000ppm display but has only been active for 15 minutes. The other just has a green flashing light to display it’s working, this has been active for 2 hours. Neither has sounded alarm so should I assume it was a false alarm? It is an old one so hoping it’s just that. The 2 new ones would detect CM straight away surely? Thank you !! 

[green-foam]

It depends on the concentration of carbon monoxide as to how long before a CO alarm will sound.

Carbon monoxide alarms should be changed as they come to the end of the working life (The working age should be listed on the detector.) So to have "an old one" could be the reason it activated.

 

[Guest Catgb29]

Hello, so our CO alarm went off at around 3:30 am it started off with 4 beeps but then they just got faster and faster until it was just a long beep, when we got up to go take a look it immediately stopped on it’s own. It probably lasted like a min or two. We pushed the test button and it beeped 4 times but it’s been a little over an hour and it hasn’t been off again?? I’m obviously too scared to go back to sleep with my family here but I also don’t know it was just a false because we never had this happened & especially since it got faster and it stopped by itself. 

[AnthonyB]

If ever in doubt when your CO alarm goes off ring the National Gas Emergency Service (Cadent) for advice on  0800 111 999

[green-foam]

If a carbon monoxide alarm activates, take it outside and wait for it to stop (Should be no more than a few minutes) Take it back inside and if it does not start again it has false alarmed.

After you bring it back inside, and it starts again, or if you have 2 or more independent CO alarms and they both activate open ALL windows and doors, if in the UK call 0800 111 999

NEVER take the batteries out, unless the unit has replaceable batteries and the new ones are infront of you.

Carbon monoxide alarms have a variety of reasons to "False alarm" Listed below, in no particular order are some reasons that can cause a CO alarm to sound

1) Unit getting old

2) Battery failing

3) Screed recently laid (As yet, no definitive answer, but newly laid screed is often the cause for CO alarms to activate)

4) Pocket/cloud of carbon monoxide (Example bonfire outside, vehicle starting close to premises)

5) Open window

6) Unit flooded/water ingress

7) Someone in the building pressed the test button (It has been known to have been done before)

8 ) Unit is getting cold

In an ideal world you should have 2 or more CO alarms, one near any fuel burning appliance, another in the hall.

[Guest Jerry]

The middle of the night false alarms are usually indicative of a cold battery. The battery may test well but under cold conditions it will set off the alarm. Take an opportunity to replace all batteries annually even if they test strong.

[Guest Worried mammy]

Hi my alarm went off tonight a few beeps then continuous beep.. it stopped itself after a minute... I took battery out, took alarm outside and then reset. How do I know if my co is present or was it a fault

 

[green-foam]

As the alarm stopped of its own accord, I would suspect it sensed something that is above its alarm threshold so it activated. If it did not stop then you may have cause for concern.

As you took it outside and removed the battery (Presumably you put the battery back in a short while later and took the alarm back indoors) and it has not activated again, I would suggest you press the test button to make sure it still works.

I would also suggest you check the age of the alarm itself (Some expire after 5 years, some after 7 years and some 10 years) as well as check the age of the battery (Some have a lifetime battery)

If the alarm still works after you have pressed the test button, and the batteries have not expired, and the unit is within expiry date, you have experienced a "false alarm"

 

[Guest Sharon Kirk]

Hi I’ve just had a combi boiler fitted in my bedroom about a week ago now the other day it kept doing two bleeps every few seconds then stoped this morning it’s done the same why is that 

[green-foam]

On 15/12/2024 at 03:23, Guest Sharon Kirk said:

Hi I’ve just had a combi boiler fitted in my bedroom about a week ago now the other day it kept doing two bleeps every few seconds then stoped this morning it’s done the same why is that 

I would suggest you contact the boiler installer to establish why your boiler beeps.

I would also suggest you buy and install a carbon monoxide alarm, one with a digital display is best such as the kidde unit.  Click here as it not only has a digital display it also has a peak level reading too.