CO detectors have a life-span of about 5 years. When they reach their end-of-life, they start a beep about once every 30-seconds to indicate they need maintenance. It is a high-pitched chirp similar to a 120VAC smoke detector with a low battery. When you hear this, it must be replaced. There is no reset or anything else that can fix it.
Side note: To test a CO detector, push-and-hold the test button until it chirps; continue holding until it sounds; continue holding until the alarm panel is tripped – it requires 20 seconds of patience
These tech tips are intended to provide insights to small nuances to help with many different products we offer. It is the small attention to detail that separates an outstanding job from an OK one. Although these apply primarily to technicians, they will help others gain insight to what the technicians do – in small doses.