My CO detector triggers an alarm with no obvious cause
Home Nura guide — category: Smoke & CO Detectors
Diagnosis
Warning: this symptom can point to a serious hardware defect. Stop using the device until the cause is found. We recommend contacting the manufacturer or an authorized repair centre before you try to use it again.
Recommended steps
Unplug it right away and stop using the device. Document the symptom (photos, video, sounds), then contact the manufacturer's support. If the device is still under warranty, keep your proof of purchase handy: this kind of failure is exactly what the warranty is for.
Repair or replace?
If the problem persists after these checks and the appliance is no longer under warranty, compare the repair estimate with the cost of a new model.
If you decide to replace it
Smoke & CO Detectors: the shortlist from our buying guide
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Best overall
Netatmo Smart Smoke Alarm
EN 14604 certified, hub-free and with a 10-year battery, it sounds even without internet and works with Apple Home and Google Home.
Photo: © Netatmo
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Best value
X-Sense XS01-WX
An entry-level EN 14604 certified Wi-Fi alarm that sends smartphone alerts without a hub, ideal for covering several rooms.
Photo: © X-Sense
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Best for carbon monoxide
Netatmo Smart Carbon Monoxide Alarm
Certified to EN 50291, it monitors CO with a 10-year battery and alerts your phone: the essential add-on if you have a gas furnace, boiler or wood stove.
Photo: © Netatmo
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Other common problems in this category
These issues affect the same type of appliance — each one comes with a diagnosis and the recommended steps.
- Smoke & CO DetectorsMy smart smoke detector beeps at random intervals
- Smoke & CO DetectorsHow long does a smart smoke detector actually last?
- Smoke & CO DetectorsThe monthly test on my smart smoke detector fails without an error message
- Smoke & CO DetectorsMy smart CO detector shows high ppm readings even though the furnace or boiler is off
Frequently asked questions
Usually, yes, if the failure shows up during the warranty period and isn't caused by misuse. A product in the Smoke & CO Detectors category bought new from an authorized retailer normally comes with a manufacturer's warranty: check its length in the manual or on the brand's website. Consumer protection rules also vary by province and territory, so keep your proof of purchase.
If you're still within the store's return window, a return or exchange is usually the fastest fix. After that, the manufacturer's warranty takes over: its customer support can arrange a repair or a replacement. Even outside the warranty, the manufacturer can often repair the device for a fee. Either way, keep your proof of purchase.
Our public methodology lowers the Nura Score /10 of any model in the Smoke & CO Detectors category whose recurring failures are documented in owner reviews. A model that breaks down too often never tops our rankings, whatever the brand.
Generally, yes. Routine maintenance, such as cleaning, replacing a gasket or recalibrating, is part of normal use and doesn't usually affect your warranty. Irreversible changes to the hardware are what can cause problems. For a product in the Smoke & CO Detectors category, stick to the steps described in the manufacturer's manual and read the warranty terms before going any further.
When a product fails in its first few months of normal use, the cause is usually a manufacturing defect. Contact the seller or the manufacturer with your proof of purchase and a description of the symptom: for a model in the Smoke & CO Detectors category that is still under warranty, this is the typical case for a free repair or replacement. Warranty terms vary by brand, so read yours.