Appliances that emit gas can release dangerous carbon monoxide if they are not properly vented. Appliances that may present this danger include furnaces, gas space heaters, clothes dryers, gas fireplaces and generators. Vent any of these appliances properly, and periodically inspect their vents to ensure they are unobstructed and working properly. Without effective venting, carbon monoxide can build up inside a home and potentially kill those inside. Your home should also be equipped with a carbon monoxide alarm that will alert you to dangerous levels of this potentially lethal gas.