Fuel burning heaters are among the most popular. Diesel heaters are commonly used with boats that use diesel fuel for propulsion engines as they have a ready source of fuel for the stove. They are available as bulkhead mount as well as floor mount, and may or may not have a fan to circulate the warmed air. All require a flue (stovepipe) that exits the cabin of your boat to dispose of the exhaust. Some heaters use natural convective draft, while others use fan-assisted draft to assist the removal of the toxic exhaust. Some of these heaters have a window, which allows you to enjoy the sight of the burning fire inside the stove. Propane (LPG) space heaters are available with “direct-vent” through fitting and flue cap, where the combustion process is completely isolated from the inside of the boat. Some of the better designs have an oxygen sensor, which will shut off the fuel supply if the oxygen in the cabin reaches a dangerously low level. A few solid fuel heaters burn charcoal briquettes or wood. These also require a ducted flue or stovepipe, as well as a source of wood or charcoal. In the past, coal was used, but modern solid fuel heaters are not designed for coal burning, as it burns too hot. [links]