Dru fireplaces hail from the Netherlands and have been successful for 250 years in the manufacture of the highest quality cast iron fireplaces and are also the largest producers of balanced flue gas fireplaces.The company is called De Koninklijke Diepenbrock en Reigers and in short, known as DRU. Dru fireplaces are equipped with a unique triple burning system
- The Primary air that is pulled in from beneath the fireplace is only used to start the burning process
- The secondary air comes in through the back of the stove and is fed through special air inlets in the back and lower chambers at the front of the unit. A portion of this takes care of the air wash of the glass window.
- A third opening at the rear of the stove ejects the tertiary air, through small holes in the back of the combustion chamber which results in almost total combustion of wood, resulting in less wood consumption.
See spec sheet here