When air is passed through a silica gel column it tends to escape via the easiest way. that is the path which has minimum resistance. This is a unwanted outcome. due to channelization silica gel that intersect the path of a air gets affected. To avoid this the column needs to be filled tight and the openings or inlet of the column should be of the diameter of the column.
I tested the Column for channelization by passing air through it for a short period of time. The change in color of the silica gel indicated the path of air. After spreading the silica gel on a flat surface. The results are as shown in the image.