The best place to put a smoke and carbon monoxide detector is on the high walls or near the center of the ceilings, and at least 10 feet away from cooking appliances. The 10-foot rule for putting detectors near cooking appliances is important because cooking can create a lot of smoke that might set off false alarms. Carbon monoxide is odorless and invisible, so it's important to have multiple detectors in your home to make sure you are alerted if there is a problem.