Steady-state and transient effective density
of cigarette smoke particles
Tyler J. Johnsona, Jason S. Olferta, Caner U. Yurterib, Ross Cabotb and John McAugheyb
of Mechanical Engineering, University of Alberta, Edmonton, Alberta, T6G 2G8, Canada
bBritish American Tobacco, Group Research & Development, Southampton, SO15 8TL, U.K
aDepartment
Poster no 3INS_P063, EAC 2015: Milan, Italy: September 6 -11, 2015
Correspondence : [email protected]
Motivation
Tobacco smoke is a complex mixture of more than 6000 compounds. It consists of gases such as carbon monoxide, volatiles, semi-volatiles and liquid like formaldehyde and nicotine, and
solid non-volatile organics for example, long chain hydrocarbons, distilled into the smoke. Droplets are typically Organic Carbon, with no Elemental Carbon present. The size of cigarette
smoke particles is around 300 nm volume median diameter (VMD) (σg=1.45) and concentration is in the order of 1011 particles per puff for fresh mainstream smoke (MS). Mainstream
tobacco smoke is subject to rapid changes by coagulation, hygroscopic growth, condensation and evaporation, and deposition losses as it transits from the cigarette to the lung. Thus, the
density of the particulate phase post-formation may change and alter its mass and mobility. The density and mobility of an aerosol particle are important physical properties for:
•Predicting particle transport in air;
•Modelling particle deposition in the respiratory tract;
•Determining other characteristics, such as particle morphology
The objective of this study was therefore to measure the effective density of cigarette smoke particles on both steady state and transient state
Experimental Set-up
In this study, the effective particle density was measured using two different systems:
Figure 1 shows smoke from 3R4F research cigarettes was collected into a Tedlar® bag and one electrical particle mobility was selected (DMA, TSI, USA) from the poly-dispersed aerosol.
The mass-to-charge distribution of the mono-dispersed aerosol was measured by varying opposing electrical and centrifugal fields (CPMA, Cambustion, UK), yielding the steady-state
effective density.
In Figure 2 smoke particles from various research and commercial cigarettes produced from direct puff sampling (Smoking Cycle Simulator, Cambustion, UK) were classified by their massto-charge ratio using a CPMA and the mobility size distribution of the classified aerosol was measured by electrical mobility (DMS-500, Cambustion, UK), yielding the puff by puff transient
effective density.
Figure 1: Experimental layout of the DMA-CPC-CPMA-CPC system
used to complete steady-state mass-mobility measurements
Figure 2: Experimental layout of the CPMA-DMS system
used to complete transient-state mass-mobility measurements
Figure 3 a) Effective density of un-aged (initial scan of each Tedlar ® bag) cigarette (3R4F) smoke determined using the DMA-CPC-CPMA-CPC system,
b) Mass and mobility measurements as compared to measurements completed by Johnson et al. (2014).
Results
±
A v e r a ge e f fe ct i v e p ar t i c le den s i t y , ( k g/ m3 )
The steady-state average effective particle density for a University of Kentucky 3R4F cigarette was 1187 113 kg/m3 (Figure 3 a) and it was independent of particle mobility-size (i.e. the
particles were spherical with constant density). This steady state value is consistent with the published data of 1120 40 kg/m3 (Lipowicz, 1988: 1R3F; Chen, 1990: 2R1F). The figure within
Figure 3a also shows that the effective density increases as the smoke particles age (t) and decreases with increasing initial particle concentrations (N) in the Tedlar ® bag. The increase of the
effective density is a simple manifestation of volatile components evaporating from the fresh smoke particles. DMA – CPMA configuration allows determination of effective density of aged as
well as fresh cigarette smoke.
The transient-state density was measured for 3R4F, 1R5F and CM6 reference
and a range of commercial cigarettes from 1–7 mg ISO pack tar. The particle
masses and mobilities measured at the maximum particle number concentration
from a 3R4F research cigarette for the fourth ISO puff are shown in Figure 3 b.
2500
2000
1500
1000
1346 ± 102 kg/m3
500
0
puff no
Cigarette
±
1
2
3
4
5
6
7
1R5F
1221 ± 88 kg/m3
1090 ± 21 kg/m3
8
1
2
3
4
5
3R4F
6
7
8
1
2
3
4
5
6
7
8
CM6
Figure 4 Average effective particle density of each ISO puff
from various research cigarettes with the CPMA – DMS
Results are in good agreement with the steady state results. It also was found
that the effective particle density was independent of particle mobility size, within
the bias uncertainty of the CPMA-DMS system, indicating that cigarette smoke
particles likely have a spherical morphology.
Figure 4 illustrates the average transient effective particle density of each ISO
puff from various research cigarettes. The transient effective particle density
(averaged from the densities measured at the peak particle number
concentrations of puffs 3 to 6) varied from 1090 to1518 kg/m3, with more than
half of the test cases falling within 1300-1394 kg/m3.
The effective particle densities from various commercial cigarettes smoked
following the ISO puffing parameters were also determined as shown in Figure
5. The number in each commercial cigarette identifier indicates the pack tar in
mg per cigarette with either carbon (C) or cellulose acetate (NC) filters. All of the
commercial cigarettes were 83 mm long, with the Super Slims (KSSS) having a
17 mm circumference and the King Sizes (KS) a 25 mm circumference.
Figure 5 Average effective particle density of each ISO puff from
various commercial cigarettes plus Tukey Grouping.
Test results for all cigarettes and test parameters considered are summarised in
Table 1. In most cases, the average effective particle density was found to
increase slightly but not significantly (Tukey 95% CI) as cigarette tar content
increased. There was no observable trend in the change in the average effective
particle density between the three categories of commercial cigarettes. Density
was typically greater for the commercial cigarettes than 3R4F. No effect on
density was seen within a single puff, with additional puffs, with cigarette format,
or between ISO and Health Canada Intense puff parameters.
Table 1: Summary of statistical analysis results with respect
to cigarettes and measurement parameters.
Conclusions
These studies offer a new method of real-time aerosol classification and have shown that smoke density is relatively consistent (within the bias uncertainty of the CPMA-DMS system) for any
cigarette type and over the full smoke particle size distribution. The particles are spheres as the effective density is independent of particle size, even with coagulation present.
References
:
•ISO 3308:2012 Routine analytical cigarette-smoking machine -- Definitions and standard conditions
•Lipowicz, P. J. (1988). J. of Aerosol Sci., 19, 587–589.
Chen et al. 1990, Aerosol Science and Technology, 12(2), 364-375
Johnson, T.J. et al. (2014). J. of Aerosol Sci., 75, 9-16.
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