Cigarette packs which leave a packing machine by moving sideways so that one of the major surfaces of each pack faces forwardly are monitored for the presence of defective envelopes during travel between two endless belt conveyors. When the monitoring system or systems detect a defective
Tobacco particles which escape from plain cigarettes and/or filter cigarettes in machines for the making of plain and filter cigarettes are partially separated from streams of suction air before such streams reach the main separator. This relieves the main separator so that the latter