Safety

How Long Does a Carbon Monoxide Detector Last?

Carbon monoxide detectors last only 5–7 years. The electrochemical sensor degrades invisibly — a 7-year-old CO detector may give false protection.

5–7 years

Quick Facts

Average Lifespan

5–7 years

Replacement Cost

$30–$50 per unit

Source

NFPA, CPSC

Overview

CO detectors have a significantly shorter lifespan than smoke detectors — most units need replacement at 5–7 years, and NFPA and CPSC guidance emphasizes that the electrochemical sensor inside degrades over time whether or not the unit appears functional. Carbon monoxide is odorless and colorless; a CO detector is the only way to know your home has dangerous levels. With 20,000+ people hospitalized for CO poisoning annually in the US and approximately 400 deaths per year, CO detectors that are past their useful life provide false protection — you believe you are safe when you are not.

Signs It Is Time to Replace

Age over 5–7 years from manufacture date (check back label)
End-of-life chirp pattern — most units have a specific chirp pattern indicating sensor expiry, different from low battery
Error codes displayed on digital units
Unit was exposed to very high humidity or extreme temperatures — accelerates sensor degradation

How to Make It Last Longer

Test monthly by pressing the test button
Replace batteries annually in battery-powered units
Record the manufacture date and set a reminder to replace at 5 years
Position at breathing height (knee to eye level) per NFPA — CO disperses throughout the air, unlike smoke which rises
Place on every level of the home and within 10 feet of sleeping areas
Never ignore a CO alarm — evacuate immediately and call 911

What Affects Replacement Cost

Basic single-function CO vs. combination CO/smoke detector (recommended for simplicity)
Hardwired vs. battery-operated — hardwired requires electrician
Smart features — WiFi alerts, voice notifications
Electrochemical vs. MOS sensor — electrochemical is the more sensitive technology

When to Replace

Replace CO detectors at 5–7 years from manufacture date — do not wait for an end-of-life alert. Most units display or stamp their manufacture date. If you cannot find the date or the detector is over 5 years old, replace it immediately. Combination CO/smoke detectors are replaced on the smoke detector schedule (10 years) BUT the CO sensor within them still degrades at 5–7 years — check the CO-specific sensor rating on your combination unit.

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Pro Tip

CO and smoke detector placement are different. Smoke rises — smoke detectors belong on ceilings. CO is roughly the same density as air and distributes evenly — CO detectors work best at breathing height (knee to eye level), typically on a wall outlet or mid-wall mount. A ceiling-mounted CO detector is not wrong, but wall mounting near sleeping areas is optimal.

Frequently Asked Questions

Where should CO detectors be placed in a home?+

Place CO detectors on every level of the home, within 10 feet of each sleeping area. Mount at breathing height (5 feet off floor or on a wall outlet) for best performance. If you have an attached garage, fuel-burning appliances (gas furnace, water heater, range), or a fireplace, these are the highest-risk areas for CO generation.

What causes CO in a home?+

CO is produced by incomplete combustion. Common sources: gas furnaces, water heaters, ranges, fireplaces, wood-burning stoves, attached garages with running vehicles, portable generators, and gas dryers. A cracked furnace heat exchanger is the most dangerous because CO enters the air distribution system directly.