Carbon monoxide is a colorless, odorless gas that is difficult to detect.
It kills about 500 Americans each year. Trying to sleep off the symptoms may seem like a good idea, but it isn't. A majority of carbon monoxide deaths occur during sleep, she said. Having the furnace checked annually by a qualified service technician can reduce risks substantially. Water heaters, clothes dryers and other gas appliances, like a gas fireplace, also should be checked regularly by an appliance specialist.