I've been researching rocket mass heaters and reading threads about them over at Permies. Apparently there is now a manufacturer of prefab rocket mass heaters, Zaug Stoves. Apparently they do not yet have EPA or UL certification for their stoves but they are in the process of obtaining both. Does anyone here follow rocket mass heater development, and if so, any thoughts on this new entry into the field? I'm not aware of any other rocket mass heater manufacturers so far.