Abstract: The making of perforations in the tubular envelopes of finished filter cigarettes or analogous rod-shaped smokers' products for the purpose of admitting cool atmospheric air into the column of tobacco smoke is regulated automatically in dependency on one or more variable parameters including the resistance of the rod-like filler of a product to axial flow of a gaseous fluid therethrough, the permeability of the entire tubular envelope, the resistance which the entire filler or the tobacco filler of a filter cigarette offers to axial or transverse flow of a gaseous fluid or to penetration of corpuscular radiation across successive increments of the filler, the resistance which successive increments of a web of cigarette paper offer to the penetration of air or light therethrough, and/or the quantity of tobacco particles in the smokers' products.