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In the laboratory, cigarettes, cigars, and pipes are smoked by machines under standardized conditions (Wynder and Hoffmann, 1967) to obtain reproducible data for the determination of various individual constituents of undiluted MS and SS. Such data provide a scientific basis for comparing tobacco products and brands. The standardized machine-smoking conditions were developed 3 decades ago to simulate human smoking behavior (Wartman et al., 1959). However, these can differ substantially from those of today’s cigarette smokers, especially in the case of filter-tipped products that are designed to deliver low yields of tar and nicotine (Herning et al., 1981).

For cigarettes and cigarette-like cigars weighing up to 1.5 g, the most widely used machine-smoking conditions in the test laboratory are as follows: one 35-ml puff lasting 2 seconds taken once a minute. The butt length for nonfilter cigarettes is 23 mm. For filter-tipped cigarettes, the total length is increased 3 mm for filter tip plus overwrap (Pillsbury et al., 1969; Brunnemann et al., 1976). For cigars, the conditions are as follows: a 30-ml puff taken once every 40 seconds and a butt length of 33 mm (International Committee for Cigar Smoke Study, 1974). For pipe smoking the test calls for a bowl filled with 1 g of tobacco and for a 50-ml puff lasting 2 seconds to be taken every 12 seconds (Miller, 1964).

Several devices have been used for generating SS from cigarettes and cigars (Dube and Greene, 1982). Among them, the Neurath and Ehmke chamber or modification thereof have been used for chemical analytic work on SS (Neurath and Ehmke, 1964; Brunnemann and Hoffmann, 1974). When SS is generated, a stream of air is sent through a chamber at 25 ml/second. At this rate, the tar and nicotine yields in the MS of cigarettes and cigars smoked in the chamber are similar to those obtained by smoking cigarettes or cigars in the open air. However, the velocity of the airstream through the chamber has considerable influence on the yields of individual compounds in SS (Rühl et al., 1980; Klus and Kuhn, 1982). In order to collect the particulate matter of MS and SS, the aerosols are directed through a glass-fiber filter that traps more than 99% of all the particles with diameters of 0.1 µm or more (Wartman et al., 1959). The portion of the smoke that passes through the filter is designated as the vapor phase. This arbitrary separation into particulate phase and vapor phase does not necessarily reflect the physicochemical conditions prevailing in MS and



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