Like smoke alarms, these should be properly installed on every floor, including the basement and within 15 feet of sleeping areas. Do not place within 20 feet of a furnace or in a humid area such as a bathroom. If the alarm sounds, gather your family, get outside, and call the fire department, says Tom Carmody, a firefighter in Cranston, Rhode Island. “Let us figure out the problem. CO is invisible and odorless, you will never know if there is a true emergency by just looking around. We will come in with our meters and determine the cause of the alarm.” Some alarms on the market detect both smoke and carbon monoxide.