Details test and examination criteria for vented room heaters, direct vent wall furnaces, vented wall furnaces, and gravity and fan type floor furnaces for use with natural, manufactured and mixed gases, liquefied petroleum gases and LP gas-air mixtures. Vented room heaters are free standing appliances designed to furnish heated air to only the space in which installed. Direct vent and vented wall furnaces are designed for incorporation in or permanent attachment to the building structure and furnish heated air directly into the space to be heated through openings in the casing. The direct vent construction is such that all air for combustion is obtained from outside the structure and flue gases are discharged outside the structure. A floor furnace is a self contained unit furnace suspended from the floor of the space being heated, taking air for combustion from outside this space, and having means for observing flames and lighting the appliance from such space.