It's all about the safety, high efficiency, and enhancing our environment when it comes to burning wood. A VaporFire " smokeless" burns Says it all .....Our Kuuma wood burning furnaces have been tested through the coldest Northern Minnesota winters and has proven it can heat an average insulated home of up to 21,000 cu. ft with our unique and simple manual draft control, you can regulate the output up to 85,000 BTU per hour. Our unit has been tested by PFS Laboratories. PFS Corporation is a third party inspection and testing agency which assists the wood-related construction industry in achieving greater quality and safety. PFS evaluates and certifies a broad range of products and structures, including all types of Engineered Wood Products, wood components and industrialized building systems.