Smoking and Tobacco Control Monograph No. 7 
machine rates used in standardized testing. Across the 32 studies, there 
appears to be a large degree of variability in the values (as shown by the 
range of values listed at the bottom of the table) that is not reflected in the 
FTC method. The average number of puffs taken per cigarette by human 
smokers was 11; FTC does not publish the number of puffs taken from a 
cigarette by the machine. Differences in puffing rates suggest that the 
FTC method probably underestimates the number of puffs taken from 
a cigarette by humans. 
It is possible to estimate the number of puffs used to determine FTC 
cigarette yield by having cigarettes machine-smoked in a research laboratory. 
The authors had a low-yield cigarette brand, Now, smoked according to the 
FTC method at the Tobacco and Health Research Institute in Lexington, 
Kentucky. Two hundred cigarettes were smoked; the average number of puffs 
taken per cigarette was 6.8. This same procedure was repeated with a high- 
yield cigarette. Camel, and an average of 8.3 puffs was taken. Thus, the 
machine took more puffs from the high-yield than from the low-yield 
cigarette, which is at odds with the human data presented in Table 1 in 
which the opposite occurs. Therefore, there appears to be a discrepancy 
between the FTC method of smoking and the way humans smoke different- 
yield cigarettes: Machines tend to puff less smoke from low-yield than from 
high-yield cigarettes, and humans tend to compensate for air dilution by 
puffing more smoke from low-yield than from high-yield cigarettes. Thus, 
humans smoke low-yield cigarettes in a manner that attenuates machine- 
determined yield differences. 
SUMMARY In conclusion, we have shown that the number and size of puffs are key 
factors that determine per-cigarette smoke exposure. Vent blocking is 
another important smoking behavior that can occur with low-yield 
cigarettes. Human smoking behavior is dynamic, not static. There is 
between-smoker variability in smoking topography, and there are dynamic 
changes in response to smoking deprivation, cigarette characteristics, other 
drugs, and situational determinants. The evidence suggests that the FTC 
method does not accurately reflect human smoking patterns. The FTC 
method takes smaller, fewer, and more widely spaced puffs than do humans, 
on average. The underestimation of puff volume is exaggerated with low- 
yield cigarettes because people tend to increase both the size and number of 
puffs drawn from lower, as compared with higher, yield cigarettes, whereas 
smoking machines decrease the number of puffs drawn while holding puff 
size constant. In addition, the IH C method does not take into account the 
important behavior of vent blocking of low-yield cigarettes. Fhus, there are 
important differences between FTC and human smoking that result in the 
machines underestimating the amount of smoke drawn by humans from 
low-yield as compared with high-yield cigarettes. 
156 
