ISO/TR 19478-2:2015 pdf download – ISO and Health Canada intense smoking parameters — Part 2: Examination of factors contributing to variability in the routine measurement of TPM, water and NFDPM smoke yields of cigarettes.
The NFDPM to nicotine ratios in Figure 3 show that the relative yield of these smoke components is little changed during the smoking of a cigarette or by decreasing the filter ventilation. In contrast, the water to nicotine ratios show that water yields are relatively unchanged for the initial puffs but then increase rapidly. The water yield also increases as the filter ventilation is reduced by vent blocking. The puff by puff water yields cannot be directly correlated with the temperature measurements in 5.3 as the cigarettes tested were not of the same design, but a mechanism to link the increased smoke water content with an increase smoke temperature can be proposed. Tobacco naturally absorbs water from the environment to a level of approximately 10 % by weight when stored at a temperature of 22 °C and a 60 % relative humidity. When a cigarette is lit, the heat from the coal drives a cloud of volatile tobacco components down the tobacco rod where they cool and condense to form the smoke aerosol. Water vapour will be the biggest vapour phase smoke component due to the release of the water absorbed by tobacco and the additional amount produced as a combustion product. Previously unpublished work (A.9) measured 200 mg to 300 mg of water per cigarette in the sidestream smoke from 84 mm long filter cigarettes.
Support for this assumption comes from the A.16 study which collected and measured the vapour phase water at the exit of the CFH using an impinger trap. The vapour phase water concentration is shown in Figure 5 for the three products tested using the HCI regime and a linear smoking machine. When making these measurements, it was assumed that the water content of the air drawn into the cigarette during puffing would contribute to the vapour phase water and needed to be subtracted to determine the true smoke yield. The A.16 study measurements were reported after subtracting the background moisture as determined from blank smokings of unlit cigarettes to the same puff number. Since the subtraction of the blank measurements effectively reduces the smoke measurements by an amount equivalent to 60 % RH at 22 °C, the remaining values will indicate the vapour phase water content to be saturated, i.e. 100 % RH, if equivalent to 40 % RH at 22 °C. The vapour density equivalent to 40 % RH at 22 °C is also indicated in Figure 5. It is evident that the vapour density of the water leaving the CFH was above the 40 % level for all three products indicating that it was still saturated. It was, therefore, above the SVD at 22 °C before subtracting the blank value and, since the smoke cannot carry water at a greater concentration than the SVD, the temperature of the smoke must have been above 22 °C.