DESC: The CBN20T Comfort Glow vent free heaters are space saving 20,000 btu natural gas blueflame heaters, these space heaters have thermostatic controls that operate by gradually modulating the heat output and flame height from the selected setting to lower settings, or pilot, in order to maintain a consistent room temperature. The CBN20T Comfort Glow vent free heaters require no electricity to run which makes them ideal for emergency and back up heating.