"Vertical chase" meaning

The term "vertical chase" is present on the definition of "differential air pressure". Does "vertical chase" refers to pipe shafts adjacent to the room or to the ceiling plenum? The definition of differential air pressure is copied below: Differential air pressure The difference in air pressure between two spaces, potentially leading, in the case of a pressure difference, to the migration of contaminants from one space to another. When using a designated smoking room nor environmental tobacco smoke control, you may need to test the differential air pressure in the smoking room with respect to each adjacent area and in each adjacent vertical chase with the doors to the smoking room closed. The testing will be conducted with each space configured for worst case conditions of transport of air from the smoking rooms to adjacent spaces with the smoking rooms' doors closed to the adjacent spaces. The test can be conducted by a mechanical engineer. The test should involve 15 minutes of measurement, with a minimum of one measurement every 10 seconds. With the doors to the smoking room closed, operate exhaust sufficient to create a negative pressure with respect to the adjacent spaces of at least an average of 5 Pa (0.02 inches of water gauge) and with a minimum of 1 Pa (0.004 inches of water gauge). Thanks in advance!