The story begins in 1975 in the cold Vermont winter with inventor Eric Darnell. His improvised dwelling was not getting warm enough despite his brand new wood stove. At the time, Darnell earned part of his living by installing specially bent steel pipes in open fireplaces in such a way that their heating capacity - without an electric fan - was noticeably increased. To do this, he used the fact that warm air rises (convection effect). From the knowledge he gained and the analysis of the weaknesses of his radiation stove, the idea of the FreeFlow hot air stove was born. The first prototype was created from the idea within a week. The heating power was overwhelming. Darnell's drafty home became evenly warm everywhere thanks to the FreeFlow. To this day, he heats his entire Vermont home with a first-generation FreeFlow. On a business trip in the early 1980s, Erhard Knöfler, an entrepreneur experienced in the heating business, discovered the FreeFlow in a Canadian logging pub. The FreeFlow was being produced in Canada at the time.

Erhard Knöfler met Eric Darnell and shortly thereafter acquired first the European distribution rights and later the patent for the stove. Erhard Knöfler founded the sales company Energetec and gave the FreeFlow stove the name Bullerjan®. Since then, the Bullerjan FreeFlow has proven itself countless times. In Europe, its quality and unique heating performance made the Bullerjan name well known. Enormous advertising budgets did not exist - the good reputation of the Bullerjan® brand was mainly created by recommendations of convinced FreeFlow users and by the passionate commitment of the first Bullerjan dealers. After the generation change in 2012, the company now operates as Bullerjan GmbH. The company's goal is to let the creativity and pioneering product claim of Eric Darnell and the entrepreneurial spirit of integrity of Erhard Knöfler live on in Bullerjan GmbH.