The answer to 'carbon monoxide detector burning smell' is that a burning smell from a carbon monoxide (CO) detector is usually a sign of a malfunctioning or faulty unit that needs to be replaced. This can indicate an electrical issue or overheating within the detector itself.
Common causes include a wiring problem, a faulty sensor, or the detector reaching the end of its lifespan (typically 5-7 years). It's important to address this issue promptly, as a malfunctioning CO detector puts your home at risk of not detecting dangerous CO levels.