ProCom 29 Inch Vent-Free Dual Fuel Firebox Insert FBNSD28T Gas Fireplace, Large, Black 26,000 Maximum BTU using Natural Gas or Liquid Propane Patented Dual Fuel Technology Thermostat Control - Automatically cycles on and off to maintain desired setting Safety Assurance: O.D.S. (Oxygen Depletion Sensor) included with automatic shut-off Battery assisted Piezo ignition