There are problems with existing wood drying kilns dealing chiefly with the circulation of heated air through the drying chamber
. There is a tendency for the heated air being directed across the lumber to be unevenly distributed leading to over drying and resultant distortion and even charring of the lumber in some locations and under drying of the lumber in other locations. This problem is also due to inadequate mixing of the heated air with recirculated air which can result in a definite temperature variance across the airstream being blown through the stacked lumber which leads to uneven wood drying kiln.