Carbon Monoxide is a product of the inefficient or incomplete combustion of fossil fuels. Poorly vented cooking appliances, furnaces and water heaters are a few of the potential generators of carbon monoxide. Carbon Monoxide is a toxic gas that you cannot see, smell, or taste. CO poisoning is the leading cause of injury and death by poisoning worldwide, with about 40,000 people treated in the U.S. annually. As the dangers of CO are better understood, more jurisdictions are requiring CO detection in areas where fossil fuel burning appliances are used.