This Mains Inter-connectable Carbon Monoxide Detector from CED addresses CO popularly known as the silent killer because it is an invisible, odourless, tasteless gas produced when fossil fuels do not burn completely, or are exposed to heat (usually fire). These fuels include: wood, coal, charcoal, oil, natural gas, gasoline, kerosene, and propane. Electrical appliances typically do not produce CO. It comes with the best sensors in the industry; electrochemical sensors. It uses electrodes in chemical solutions that sense changes in electrical currents when carbon monoxide is present, and they sound an alarm.