Every one in a while, you might run into a giant furnace with monstrous-looking ducts running in all different directions. These gravity furnaces, also known affectionately as “octopus furnaces”, use the force of convection to push air throughout a building. They lack the blower fan inherent to forced-air furnaces, which means they’re quieter and kick up less dust, but the benefits pretty much stop there. They are notoriously inefficient and most have outlived their life expectancies. To find out inspection tips and more, check out our new article on gravity furnace inspection.