A web which is converted into wrappers of plain or filter cigarettes, or the wrapper or each cigarette is perforated by needles, teeth, punching tools, sparks or laser beams prior to arrival of corresponding cigarettes at a pneumatic testing station. The testing device at such station transmits signals which denote the permeability of successive wrappers, and the signals are compared with a reference signal denoting the desired permeability of wrappers. If the monitored permeability deviates from the desired permeability, the device which makes holes in the web or in the wrappers is automatically adjusted to change the combined area of holes.