The ZL-2 steam air heater comprises seven components: radiant fin tube of steel and aluminum + electrical steam valve + overflow valve + heat isolation box + ventilator + Fresh air valve + electrical control system. It is particularly planned for supporting the left and right loop drying room. For instance, in the 100,000 kcal model drying room, there are 6 ventilators, three on the left and three on the right. When the three ventilators on the left rotate clockwise, the three ventilators on the right rotate counterclockwise in a cyclical consecutive manner, creating a relay. The left and right sides function as air outlets and inlets sequentially, removing all the heat produced by the steam heater. It comes with an electric fresh air valve to supplement fresh air together with the dehumidification system in the drying room/drying area.