Carbon Monoxide Detector
A carbon monoxide alarm lasts 5 to 7 years — then the electrochemical sensor is spent and the whole unit must be replaced, even if it still powers on.
Why the sensor expires
A carbon monoxide alarm does not measure gas with a simple switch — it uses an electrochemical sensor, a tiny sealed cell whose chemistry slowly runs down whether or not it ever meets any CO. After five to seven years that cell can no longer react reliably, so the alarm may stay silent when it matters most. This is why every unit certified to EN 50291 carries a fixed end-of-life date: the sensor cannot be cleaned, recharged or renewed.
How to read the replace-by date
Look on the back of the unit for a printed "replace by" date or a manufacture date. Count five to seven years from manufacture, or simply trust the printed deadline. When that date passes — or when the alarm gives a distinct end-of-life chirp, usually a double beep every 30 seconds — the whole device goes in the bin, sensor and all.
Placement and monthly testing
Fit a CO alarm in every room with a fuel-burning appliance — boiler, gas hob, wood stove, fireplace — and near sleeping areas, at breathing height rather than on the ceiling. Press the test button once a month, and never treat a sounding CO alarm as a false alarm: leave the building and call the emergency services.