What to do if your carbon monoxide detector keeps going off


The most important thing any householder should do when they hear an alarm from their carbon monoxide detector is ignore it or assume it’s nothing but a false alarm or a malfunction. Naturally both latter things can happen, but it would be foolhardy, and potentially fatal, to make such assumptions. If the carbon monoxide detector alarm beeps, then assume it’s a genuine emergency and take the appropriate action. Why? Well, simply because the alternative doesn’t bear thinking about. Carbon monoxide can’t be seen, tasted, or smelt; it’s an odorless, colorless deadly gas that’s why it’s grimly known as the ‘silent killer’.

If your carbon monoxide detector alarm beeps, assume there is carbon monoxide present in the property and take the following steps:  

  • Remain calm and open all doors and windows to maximise ventilation on the property. 
  • Turn off any fuel burning appliances –gas boilers, furnace, wood stoves and cookers etc, but only where it is safe to do so. 
  • Vacate the property as soon as is practical taking all other occupants and pets with you. For their safety, notify any neighbour in adjoining properties about the potential of a carbon monoxide build-up in your home. It won’t necessarily affect them, but instances have been found where carbon monoxide gas has seeped through walls and floors into adjoining properties. 
  • Contact the Gas Emergency Services or a local Gas Safe Registered Engineer or other qualified technician to check for the possible source of carbon monoxide
  • Get medical help for anyone experiencing carbon monoxide poisoning symptoms such as nausea

What are the symptoms of carbon monoxide poisoning?

The main symptoms of carbon monoxide poisoning are:

  • Persistent headaches
  • Dizziness
  • Nausea/vomiting
  • Stomach pains
  • Difficulty breathing
  • Tiredness
  • Sudden collapse
  • Brain damage
  • Confusion

What can cause a carbon monoxide detector to malfunction and issue false or erroneous alarms?

The first thing to establish is what exactly is meant by ‘false alarm’? A false alarm is when a CO detector alarm starts chirping where no carbon monoxide is detected by your engineer. Why would this happen? Well, there could be several reasons for this:

  • The carbon monoxide detected might not have originated in your property or be due to a fault with one of your appliances. It might have been triggered by a CO leak in in a neighbouring property, seeping through the walls or floor into your property. It might even have been seeping from an unpointed internal chimney stack and entered your premises through a shared loft space. 
  • The carbon monoxide alarm battery may have exceeded its shelf life and need replacing. Once the batteries expire, the performance of carbon monoxide detectors can become very erratic. Of all carbon monoxide detectors faults this is probably the most common. 
  • Excessive moisture in bathrooms and kitchens may have set off your CO alarm. It’s worth emphasising that CO alarms should never really be installed in any areas where excessive steam might be generated.
  • Lead acid battery chargers produce hydrogen gas and can set off CO detector alarms. This is worth bearing in mind if you are charging your caravan/boat battery at home.
  • Believe it or not, freshly screeded floors emit a gas that can set off carbon monoxide alarms.
  • The carbon monoxide alarm that you install may not be suitable for the type of premises in which it is fitted. CO detector/alarms installed in caravans, tents, or boats are necessarily different to home CO detector alarms and should comply with Kitemark Standard BS EN50291-2. Alarms tested to BS EN50291-1 are only suitable for use in home environments, not for camping and caravanning.
  • Rarely a heavy smoker or vaper can trigger a CO alarm if the room where they are sitting is poorly or inadequately ventilated. 
  • Homes that adjoin busy roads and thoroughfares can sometimes experience higher levels of CO in the home when windows are open. Passing traffic fumes contain a high proportion of CO gas and these could enter properties through open doors and windows and trigger CO alarms.  
  • The sound that your alarm is making may not be the alarm sound you assume it is. It might not necessarily be the alarm sound to alert you to any dangerous level of CO present – though it’s always safer to make that assumption than not for safety’s sake. Most alarms have several audible sounds to indicate things like low battery warnings or that there is a fault with the alarm. When you install an alarm read the user manual and get to know what the different sounds indicate. Keep the manual safe so that you can refer to it should the alarm go off.

Why is my carbon monoxide detector beeping?

The most obvious reason for a beeping carbon monoxide detector is flat batteries. Flat or low batteries will hinder the functionality of the device, so it’s only fitting that your detector gives off a faint beeping sound to warn you of this. If the batteries are below par, change them and see if the beeping then stops.

Why is my carbon monoxide detector beeping every 30 seconds?

When your carbon monoxide alarm reaches its end of its shelf life, the alarm will beep every 30 seconds to inform you the alarm unit or its batteries needs to be replaced. The alarm will generally beep after 7 to 10 years of use depending on the quality of the unit. However, this 30 second beep can sound very similar to a low battery alarm., so check the handbook for more information. If the information you require is not available, replace the batteries first and see what happens.

Why do carbon monoxide detectors expire?

In an ideal world, carbon monoxide detectors would offer lifelong service. Sadly, we don’t live in an ideal world, and unfortunately most products have a shelf life. Carbon monoxide detectors won’t last forever and will expire. Why is this the case? Well, over time, the components inside the detector degrade. The average lifespan is 7 years, but it’s sensible to think about replacing your carbon monoxide alarm once every 5 years if possible. Most CO detector alarms are relatively cheap (link to Best Carbon Monoxide Alarms, 2021 when posted), so replacing them shouldn’t be all that financially onerous. 

Cleaning a carbon monoxide detector and sensor

When cleaning your carbon monoxide detector, take the opportunity to perform other maintenance tasks such as changing the detector’s batteries and pressing the detector’s test button.

  • Wipe down the outside of the detector with a dry, soft cloth. Wipe away any large pieces of dust or debris from the area around the sensor. Slightly dampen the cloth if there are any stubborn stains, but don’t be too vigorous. Avoid getting moisten on the detector’s sensor.
  • Attach the soft brush attachment to your vacuum hose. Gently vacuum the carbon monoxide detector, focusing on the area around the sensor. Try not to touch it with the hard plastic of the vacuum attachment as it is sensitive and can be easily damaged.
  • Spray the area around the sensor with canned air or a gas duster. The canned air will take care of any remaining debris without causing damage.

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