The answer to 'why is my carbon monoxide detector burning smell' is that a burning or acrid smell coming from your carbon monoxide (CO) detector is typically a sign of a malfunction or internal failure. This could be caused by an electrical short, overheating, or a problem with the internal components.
If your CO detector is emitting a burning smell, it's important to take it seriously and address the issue right away. Carbon monoxide is an odorless, colorless gas that can be deadly, so a malfunctioning detector could put your family at risk. You'll want to unplug the device, open windows for ventilation, and call a professional HVAC technician to inspect and repair or replace the unit.