Have the heater for a small basement room (approx 12sqm) concerned and thought if one of Vorrezensenten 25m² can heat it, it is also sufficient for a half-sized room. Not even close. More than a gentle breeze came because not get out - even after just 30min. Presumably, the device is defective. But will not change the fan but let me refund the purchase price, because if the device comes from the factory and does not work, I do not know how long the durability is.