Dyna-Glo IR18NMDG-1 18,000 BTU Natural Gas Infrared Vent Free Wall Heater Natural Gas Ready (Fuel conversion not permitted) Infrared Technology works by radiating heat to warm objects first - Similar to the sun 6,000-18,000 BTU's/hr variable heat output for up to 700 sq. ft. Variable control knob offers the most customizable heat settings LOW - 6,000 BTU MED - 12,000 BTU HI - 18,000 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