Furnace atmosphere circulation is at the heart of the heat treatment process. Without thorough circulation of gases, heat treatment processes cannot achieve consistent results in terms of parts surface quality and mechanical properties. The uniformity of the atmosphere plays a major role in maximizing performance of the heat treatment recipe. How well that is achieved translates directly into the quality of the actual process. Proper circulation helps the furnace heat the treatment atmosphere and promotes the thermochemical reactions that take place during the heat treat process. Convection, which is the main mechanism of stimulating atmosphere reactions to achieve surface properties as well as the combination of convection and radiation for heat transfer, are both determined by the efficiency of atmosphere circulation. The paper will discuss traditional atmosphere circulation, and compare this to new gas-mixing technology from Linde, highlighting data from recent installations and actual operating experience.