Life-safety devices · Carbon monoxide alarm
How long do carbon monoxide detectors last?
Kidde's answer for its own alarms is seven to ten years, depending on the model — shorter than a smoke alarm, because the electrochemical cell that senses carbon monoxide wears out whether or not it ever sees any. The alarm says so itself: ten years after first power-up it beeps twice every thirty seconds, and Kidde's manual adds the part that matters — "It will not detect CO in this condition." The warranty on the same unit also runs ten years, but it covers defects in a new alarm, not a sensor using itself up on schedule.
Updated
The gap: warranty ends at 10 years; typical service life ends around 10 years. The paper and the typical service life end together — an unusually honest term. Warranty document (Kidde, checked 2026-08-27)
Typical service life: 7–10 years
Kidde's phrasing: "Kidde carbon monoxide alarms have a proven life of seven to ten years, depending on the model type." It draws the line by date rather than by wear — "As of 2013, all Kidde carbon monoxide alarms have a 10-year life," with three named model exceptions, and "If your CO alarm was manufactured before 2013, it has a seven-year life." Kidde's warranty pages carry the same split from the other side: most of its alarms come with a 10-year limited warranty, while some of its carbon monoxide alarms have a 7-year one. InterNACHI's undated baseline chart is far more conservative than any of this, listing carbon monoxide detectors at 5 years.
Tier 1 · manufacturer document Range from Kidde — When Should I Replace My Carbon Monoxide Alarm?, checked 2026-08-27.
A CO alarm is an indoor instrument with a wet-chemistry heart, and it is unusually sensitive to where it lives. Kidde rates the KN-COB-LP2 for 40°F to 100°F and 10–95% relative humidity non-condensing; garages and unheated spaces sit outside that band, and they are also where solvents, exhaust and aerosols concentrate. The same alarm in a hall outside a bedroom and in an attached garage is not the same alarm two years in.
What the warranty paper actually says
Kidde (Carbon Monoxide Alarm Model KN-COB-LP2) publishes a 10-year limited, non-transferable, conditional warranty. Kidde warrants the product — batteries expressly excluded — free of defects in material and workmanship for ten years from date of purchase, with the remedy at Kidde's discretion: replace it, repair it, or replace it with a repaired unit, returned postage-paid to Mebane, North Carolina with proof of purchase date. A replacement carries the remainder of the original period or six months, whichever is longer. It is void if the alarm was damaged by accident, unreasonable use, neglect or tampering, and it extends to the original consumer purchaser only. The one thing it does not reach is the sensor reaching its end-of-life at ten years — under this paper that is not a defect, it is the alarm behaving as the same manual says it will.
The warranty document itself , checked 2026-08-27.
What shortens it
- The sensor's own chemistry — an electrochemical cell ages on the calendar whether or not the alarm ever detects anything, which is why Kidde's figure is a life and not a duty cycle
- Silicones, solvents, aerosols, paint fumes and household cleaning products, which contaminate the sensing cell
- Garage, kitchen and bathroom mounting, where exhaust, cooking vapors and steam sit on the sensor
- Conditions outside the rated indoor band — Kidde's guide gives an operating range of 40°F to 100°F and 10–95% relative humidity, non-condensing
- Age of the model, not the household: Kidde's alarms made before 2013 carry a seven-year life, its later ones ten
- Stretching out the end-of-life signal — Kidde's End of Life Hush silences the chirps for three days at a time up to a total of 30 days, after which, in the manual's words, "the End of Life signal cannot be 'Hushed.' The alarm must be replaced"
- Removing the back cover, which Kidde says voids the warranty
Signs of wear to look for
- Two beeps every thirty seconds with a flashing red LED — Kidde's end-of-life signal, which its manual pairs with the warning "Replace the alarm immediately! It will not detect CO in this condition"
- ERR or END on a digital display, which Kidde lists as the end-of-life codes on its display models
- Chirping that a fresh battery does not stop — on a CO alarm this points at the unit, not the cell in it
- A "replace by" date already written on the side label, which Kidde's manual asks you to fill in at installation, or a manufacture date seven to ten years back
- No response at all from the test button, which is the only function check the manual asks of an owner
- UL's guidance to code officials is worth knowing here: newer CO alarms produce an end-of-life signal distinct from the CO alarm pattern, but it may sound the same as other trouble signals such as low battery — the manual for your model is what tells the two apart
An alarm in full alarm is not a maintenance question. UL's guidance to code authorities is blunt — whether or not anyone is feeling symptoms, never ignore the alarm — and the response is to get everyone into fresh air and call the fire department. Why a house is producing carbon monoxide at all is a combustion-appliance and venting question for the fire service or a qualified inspector: that is an inspection question, not a web-page question.
Related life-safety devices
- Smoke alarm 8–10 yrs
- Fire extinguisher 12+ yrs