http://articlehubworld.com/product-review/tank-top-portable-propane-heater/ Propane. Variable output of 6000, 9000, and 12,000 BTU hr. High Medium Low regulator, safety shutoff and soft nose P.O.L. For direct connection to 4 20 lb. bulk cylinder. High fire time: 36 hours Sat, 04 Sep 2010 05:24:19 MSD en