Under normal conditions, propane appliances will release virtually no carbon monoxide, which is an odorless, invisible gas that can be dangerous or even deadly in high concentrations. When such appliances are malfunctioning or being used incorrectly, it is possible for them to produce carbon monoxide. Always have a functioning carbon monoxide detector in any home with appliances that use propane, natural gas, or home heating oil, and do not use appliances rated for outdoor use indoors.