Smoking and Tobacco Control Monograph No. 7 
the particle phase of the smoke is collected on glass fiber (Cambridge) filters, 
and the gas phase (passing through the filter) is collected in gas sampling 
bags. Carbon monoxide is measured in the gas sampling bags. The filter is 
weighed to yield a measure of total particulate matter (TPM) and is analyzed 
for nicotine and water content. Tar (or nicotine-free dry particulate matter) 
is computed by subtracting the weights of nicotine and water from the 
weight of TPM. 
The principal reason for using smoking machines is to maximize the 
reproducibility of results (DeBardeleben et al., 1991). This is particularly 
important for quality control and product comparison and is essential for 
interlaboratory comparisons. However, machine smoking is limited in that 
it provides results accurate only for the specific set of smoking conditions 
employed by the machine. 
Smoking parameters used in the FTC procedure are based largely on 
empirical observations of smokers reported by Bradford and colleagues 
(1936). They suggested a nominal 35-mL ("mL" is used interchangeably in 
the literature with "cc") puff volume of a 2-second duration taken once per 
minute to a 23-mm butt length. Current FTC smoking conditions (Federal 
Trade Commission, 1994) specify a puff volume of 35 ± 0.5 mL, a puff 
duration of 2.0 ± 0.2 seconds, and a puff frequency of 1 per 60 ± 1 second. 
Butt length is specified as 23 mm for nonfilter cigarettes and the length of 
filter overwrap plus 3 mm for filtered cigarettes. The international standard 
method (Thomsen, 1992) ISO 3308 currently uses the same conditions but 
requires more stringent tolerances. Puff volume is 35 ± 0.25 mL, puff 
duration is 2.0 ± 0.05 second, and puff frequency is 1 per 60 ± 0.5 second. 
Machine-smoking parameters are only one of several conditions that 
have been specified to constitute standard FTC testing. Other conditions 
include the number and manner of selection of cigarettes to be tested, 
cigarette conditioning (see below), the smoking environment, and the 
methods and instrumentation used. FTC testing specifies the analysis of 
100 cigarettes selected at random from two packages purchased at each of 
50 geographical locations throughout the United States. Cigarettes must be 
conditioned at 60 percent relative humidity and 24 °C for at least 48 hours 
before smoking and must be smoked in a room maintained under the same 
conditions. Smoking is performed using a Phipps and Bird 20-port linear 
smoking machine, thus specifying by default that "restricted" rather than 
"free" (butt end closed rather than open to the atmosphere between puffs) 
smoking be performed. Finally, the air flow across the cigarettes must be 
reproducible and controlled to control the rate at which the cigarette burns 
between puffs. 
The introduction of cigarettes with ventilated filters has made it 
necessary to pay additional attention to the depth to which the cigarette is 
inserted into the holder. The cigarette must be inserted sufficiently deep to 
hold it firmly for the smoking j)rocess but not so deep as to occlude the 
ventilation holes. 
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