CO detectors measure CO levels in the environment and sound an alarm to warn you to ventilate the affected area. Two basic types of CO detectors. CO detectors are either battery operated or electric. Most CO detectors on the market use one of the following three sensor types. 1. Electrolytic Sensor Detectors-This type of sensor is extremely sensitive to detecting CO in the home. Although it is the most efficient type of CO detector, it is rarely used due to its significant cost. 2.