All gas appliances - stoves, furnaces, water heaters, etc. - produce carbon monoxide. Carbon monoxide is toxic to humans. At Insight, we test CO in your home and at the output of your gas appliances, to give you the assurance that your home is not making you sick and your appliances are working properly. These appliances and their supply pipes can also leak gas into your home and, even at low levels, cause irritation and sickness in children, adults, and the elderly. Insight identifies these common issues that contribute to 'sick' homes.