There are three basic types of CO sensors - biomimetic, metal oxide, and electrochemical. No matter which detector you choose, it's important to know where to install and how to maintain it. It's best to have one detector on each floor of a house. Be careful that they are not obstructed by furniture or draperies. If you plan to purchase only one alarm, install it in the hallway outside the sleeping area.
Detectors measure carbon-monoxide concentrations and exposure time.
They are designed to sound an alarm before you're exposed to an unsafe level. Working much like home smoke detectors, carbon monoxide detectors will sound an alarm when levels within the home go beyond 10 parts per million for eight hours or 100 parts per million for five minutes. A level of 40 parts per million is considered dangerous. By checking the readout, resetting the alarm and checking again, you can determine whether there is a real problem. Sometimes called chemioptic, the technology uses gel-coated discs that darken in the presence of CO, tripping the alarm.