KILN DRYING HANDBOOK. 
53 
invented and developed at the Forest Products Laboratory. Figure 11 
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indicate the direction of the circulation when the left lines are open. 
With the right lines open the circulation will be reversed. 
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Fig. 10. — Cross section of internal-fan kiln. A number of disk fans are mounted at 
intervals upon a shaft extending the full length of the kiln. 
PILING LUMBER FOR KILN DRYING. 
Lumber to be kiln dried is usually piled in layers with strips or 
stickers between each two layers. Sometimes short stock, like spoke 
billets, handles, and shoe-last blocks, is simply dumped into the kiln 
without any attempt at orderly arrangement/ This method is apt to 
produce irregular drying unless only small amounts are dried at a 
time. The piling and sticking of the lumber should provide suitable 
air passage between the boards in each layer and between layers, and 
