The primary, secondary and tertiary air is completely preheated, passing first under the base and then through a cavity located at the bottom of the combustion chamber. This very high temperature air is able to combine with carbon monoxide, not totally burned in the first phase of combustion, generating a secondary and tertiary combustion that minimizes polluting emissions, so as to reach the 5 stars as an environmental class and be certified for the thermal account with the greatest rewarding factor. Characterized by a patented anti-lock anti-locking vertical door, which can also be opened laterally for cleaning the glass. The inner surface of the door allows the passage of an air veil to avoid the smoking of the glass.