UL 1673 covers electric space heating cables rated 277 volts or less and intended for installation in accordance with the National Electrical Code. These cables are to be installed in ceilings of enclosed structures or within or beneath floors of enclosed structures where the floor is constructed of noncombustible material, concrete, or asphalt. UL 1673 does not cover pipe heating cables, cables intended for snow melting and de-icing, heating panels, or heating panel sets.