Mr. Heater, Corporation, 20,000 BTU Vent Free Blue Flame Propane Heater, MHVFB20LPT (F299720) 20,000 BTU Liquid Propane heater to heat spaces up to 500 square feet Blue flame burner for even convection heat. Automatic low oxygen shut-off system (ODS). CSA Certified Operating this heater at altitudes over 4,500 FT above sea level could cause pilot/ODS to shutdown the heater. Theromostat, legs and wall mounting hardware included