The answer to 'when to replace carbon monoxide detector' is that carbon monoxide (CO) detectors should be replaced every 5-7 years, or as recommended by the manufacturer. CO detectors have a limited lifespan and can become less effective over time, so it's important to replace them regularly to ensure your home's safety.
Most CO detectors are designed to last 5-7 years with normal use. As the detector ages, the sensors that measure CO levels can become less accurate and responsive. Replacing the detector every 5-7 years helps ensure it will reliably alert you to dangerous CO levels in your home. Some detectors may have a shorter lifespan, so always check the manufacturer's recommendations.