Mr. Heater big Buddy has 18000 BTU/HR with the capacity to heat up to 400 square feet of space for up to 220 hours. Dual-Heating System (DHS) combines radiant heat comfort with convection heat airflow for maximum heating efficiency. Multi-position heat settings of 4000 and 9000 and 18000 BTU/HR control comfort level. Built-in oxygen shutoff sensor and tip-over switch ensures indoor safe operation. Certified by CSA International (American Gas Association).