A process for controlling airflow in a wood drying kiln having a charge receiving chamber for receiving a charge of lumber and circulating fans operably mounted to the structure and configured to produce airflow within the charge receiving chamber as defined by claim 21, wherein the step of positioning at least one row of elongated resilient brush bristles having sufficient density to limit passage of air laterally through the row within the chamber to yieldably engage successive charges of lumber placed within the charge receiving chamber is accomplished by mounting two rows of brush bristles on each of the baffles, the rows of brush bristles on each baffle being spaced apart by a distance of less than approximately 1.5 inches or 3.81 centimeters.