Dyna-Glo BF10NMDG 10,000 BTU Natural Gas Blue Flame Vent Free Wall Heater Natural Gas Ready (Fuel conversion not permitted) Blue Flame Technology works by convecting heat to warm the air the same way as a central heating system 5,000-10,000 BTU's/hr variable heat output for up to 300 sq. ft. Variable control knob offers the most customizable heat settings LOW - 5,000 BTU MED - 7,500 BTU HI - 10,000 BTU No electricity required allows for reliable back-up heating incase of an emergency situation Separately sold optional fan (WHF100) improves the amount of square footage the heat reaches in a quiet, yet powerful way! Separately sold optional base legs (WBL100) allows for stable floor mounting 1 Year Warranty