Minimal maintenance is required to keep carbon monoxide detectors functioning. CO detectors with replaceable batteries require new batteries every six months, and many units have a built-in warning alarm and light when it's low on power. After five to seven years, most CO units need replacing. Refer to the instructions or manufacturer's website to find out exactly when to replace it. It's also a good idea to wipe the carbon monoxide detector down with a dry cloth twice a year to ensure that dust or dirt doesn't obstruct the alarm's sensing chamber.