Carburizing, carbonitriding and nitriding in retort furnaces is made in heat-resistant sealed retort, suspended inside the furnace. Due to the use of modern components and materials, innovative design solutions for the shaft-type retort furnaces have a uniform temperature distribution in the heating zone, a precise adjustment of the digital process, a high uniformity of forming cementing layer. The furnaces of this series the fans are used for highly efficient mixing of the furnace atmosphere. Additionally, the furnace can be equipped with baskets for the load and SCADA system. Furnaces of this type can be a gas or electrically heated.