Comparison of the effectiveness of tape and simple
holder based vent blocking devices when used in
intensive smoking regimes.
I.Tindall
T.Mason
L.Dutertre
(Cerulean, Rockingham Drive, Linford Wood East, Milton Keynes,
MK14 6LY, United Kingdom)
(Cerulean, Rockingham Drive, Linford Wood East, Milton Keynes,
MK14 6LY, United Kingdom)
(Laboratoire National de métrologie et d'Essais, 29, avenue Roger Hennequin 78197 Trappes CEDEX – FRANCE)
Abstract
The complete blocking of ventilation features has been mandated in Health Canada standards for
a number of years. In contrast some US states mandate blocking of 50% of ventilation holes
during smoking and the current ISO standards require no ventilation blocking. However as
smoking methods are reviewed it is becoming increasingly likely that the current ISO method will
be supplemented by some form of intensive smoking regime which will include vent blocking.
However some difficulties arise in the manner of vent block prescribed by the Health Canada
method, namely the use of adhesive tape to block holes.
This is a time consuming activity that relies on the skill and dedication of the person taping. A
conceptually simpler method, that would reduce the human element present in applying tape for
vent blocking, would be to devise a holder that occludes the ventilation holes and is equivalent to
the taping method.
A simple holder was devised that allowed occluding of the ventilation holes and was suitable for a
range of product diameters. This holder was compared against the tape method using 15 different
commercially available brands of different styles and constructions. Comparisons were made on
the basis of pressure drop of taped and holder based rods and smoking yields.
Statistical equivalence was shown with a 95% confidence limit for paired t-tests for pressure drop
measurements and two sample t-tests for smoked rods.
Introduction
Smoke yield data, whether submitted as part of a regulatory function or used to further product
design, relies on consistent generation methods. Modern mechanical smoking machines offer a
flexible tool for generating consistent puffing profiles and airflows that define repeatable
conditions under which smoke is generated. In the main most “routine” smoking has been
conducted under sets of conditions mandated by bodies such as FTC, ISO or other equivalent
regulatory bodies.
Observed yields of CO and nicotine free dry particulate matter (NFDPM), or tar, have depended
in some cases on design features such as tip ventilation, the addition of small holes to the filter tip
that dilute the smoke stream during smoking. It has been recognised that some smokers may
deliberately or accidentally block the ventilation features during smoking and so yields measured
under ideal conditions can underestimate the delivery received by the smoker. This realisation
has in part given rise to the so called intensive methods adopted by Health Canada [1] and some
states in the USA where ventilation holes are blocked or partially blocked and a much larger
smoke puff is drawn during smoking.
In the review of the ISO3308 [2] standard by ISOTC126 the augmentation or substitution of the
current method with a more intensive method has been proposed. In the two possible methods of
100% vent blocking and 50% vent blocking currently used the ventilation blocking is
accomplished through the use of adhesive tape to the butt.
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Such a process requires some skill and concentration to consistently and effectively apply tape to
the holes. When dealing with large numbers of tests this becomes expensive and provides
additional variability to the sample preparation in the form of inconsistent taping. Moreover as the
rod diameter decreases the challenge becomes greater for the person applying tape.
A simple to use holder that is equivalent to the taping methods and is repeatable and suitable for
different diameters and styles of rods would seem desirable for manufacturers and regulators of
cigarettes alike. A design for such a simple holder was developed and examined for equivalence
to the current taping methods used in Canada and Massachusetts.
Experimental
A 100% holder was devised based on the holders used to hold cigarettes during routine ISO
smoking. In the variant used the holder was extended in length and a series of labyrinth seals and
spacers devised such that the front of the cigarette was sealed from atmosphere as was the rear
of the butt. In this way 21mm of cigarette butt was occluded and excluded from the atmosphere.
Different diameters of cigarette could be accommodated by the use of labyrinth seals with
different orifices which we colour coded for simplicity. In the test “blue seals” were used for
standard circumference rods and “orange seals” used for the slim products tested Figure 1.
Figure 1: Intensive holders for different diameter rods
Samples of cigarettes were selected on the basis of test buys and were chosen to represent a
number of construction styles. See table 1 for samples tested.
To compare the efficiency of the holder method of occlusion and the taped method two tests were
performed. Firstly the two methods were compared by measuring the pressure drop of the rod in
a Cambridge filter pad holder either in the taped or holder based configuration. This test was
conducted using a modified Cerulean PD express. This allowed paired comparisons of rods as
each rod under test was numbered and tested first in the holder and then with taping. It was
noted that the taping method was not always effective and the rods had to be checked that the
tape had adhered correctly and uniformly about the butt.
A second series of test were performed using a Cerulean SM450 20 channel linear smoking
machine. Here rods that had been conditioned at standard ISO conditions were smoked using an
intensive regime of 1 puff per 30 seconds of 2 seconds duration and 55ml volume (bell shaped
puff profile). Three cigarettes were smoked into each pad. Air flow was set to 200ml/min coaxial
with the smoked rod. Cambridge filter pads were weighed before and after smoking on a 5 figure
balance. 10 channels in the smoking machine were dedicated to taped rods and the remaining 10
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channels dedicated to holder based rods to ensure that identical smoking conditions were
experienced by the two sets of occluded cigarettes. Blue seals in the holders were used for
standard circumference rods and orange seals used for slim rods.
The TPM, CO per cigarette (corrected for atmospheric conditions) and average puff count was
collected for each test sample. Data was entered into Minitab together with PD data and
processed accordingly. Comparisons were made on the basis of 95% confidence limits with either
two sample or paired T tests.
Table 1: Test samples
Brand
Type
Id
A
B
C
D
E
F
G
H
J
K
M
N
P
R
S
Standard KS
Slim KS 98mm
Standard KS
Standard KS
slim 120s
Standard KS
Standard KS
Standard KS
Standard KS
Standard KS
Slim
Standard KS
Standard 100
Standard KS
Standard 120
Nominal
yield
NFPDM
5mg
5mg
7mg
1mg
?
5mg
1mg
7mg
6mg
1mg
1mg
9mg
?
8mg
?
Construction
Menthol
Menthol
Menthol
Recess filter
100% vent
blocked test
PD
Smoke
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Results
14 brands were compared.
PD test results are shown in figures 2 and 3 respectively. It can be seen that means and spread
of data is similar for holder (pink) and taped rods (blue). Statistical comparison of the two groups
was made using two sample and paired T tests with a 95% confidence limit. The significance
figure for the test is shown in table 2. All brands are shown to be statistically comparable at the
95% confidence limit in both forms of the T test.
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Figure 2: Pressure drop comparison for “standard” diameter products
Figure 3: Pressure drop comparison for “slim” diameter products
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Table 2: comparative effectiveness of vent blocking methods. With confidence limits set at
95% the p-value will be greater than 0.05 if the two sets of data are statistically equivalent.
Brand
A
B
C
D
E
F
G
H
J
K
M
N
P
R
Significance figure (p) 95% confidence limits
T sample T test
Paired T test
100% blocking
100% blocking
0.614
0.135
0.645
0.810
0.974
0.883
0.418
0.212
0.765
0.175
0.778
0.296
0.269
0.095
0.410
0.053
0.871
0.201
0.919
0.890
0.881
0.058
0.844
0.622
0.906
0.273
0.890
0.083
Smoking tests were conducted on 15 brands, plots of comparative yields for CO and TPM are
shown in figures 4 and 5 respectively. The comparative 2 sample T test significance figures with a
95% confidence limit are shown in table 3.
Figure 4: Carbon monoxide yield comparison all brands
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Figure 5: TPM comparison all brands
Table 3: Statistical match of yields for taping and holder based occlusion. With a
significance level of 95% set the p-value will be greater than 0.05 if the two sets of data are
statistically equivalent. Where statistical significance is not obtained the data is
highlighted in red.
Brand
A
B
C
D
E
F
G
H
J
K
M
N
P
R
S
Significance figure (p-value) for two sample T test 95%
confidence limit
TPM
Puff count
CO/cig
0.077
0.770
0.284
0.288
0.295
0.595
0.087
0.680
0.158
0.689
0.060
0.184
0.904
0.469
0.167
0.153
0.237
0.450
0.065
0.074
0.876
0.096
0.020
0.093
0.656
0.070
0.837
0.050
0.530
0.273
0.007
0.419
0.028
0.081
0.314
0.277
0.385
0.211
0.305
0.071
0.834
0.285
0.542
0.055
0.575
The smoking of brand M was repeated ensuring that the same level of occlusion was obtained by
the taping and holder methods.
After smoking some of the filters were sectioned to observe the level of discolouration of the
butts. It was notable that the level of discolouration was greater for the intense smoked rods
(figure 6) and comparable between the holder and taped rods.
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Discussion
Figure 6: Butt discoloration from various smoking methods
The PD measurements of the two 100% occlusion methods showed excellent agreement
provided the correct diameter seal is used for test. This method could be used in paired T testing
– more stringent that two sample T testing – and does not rely on the natural variability of
smoking tests. Hence a high degree of confidence in the methodology could be gained before
progressing to smoke testing.
The methodology in the smoke test was designed to minimise any experimental artefacts and
generally good agreement was achieved between taping and holders with small anomalies in puff
count for brand H. The major discrepancy for brand M was resolved when identical levels of
occlusion were applied to the two tests. In these tests a readily available 23mm wide tape was
used although Health Canada specifies 19mm wide tape [1] whilst the occlusion device covers
21mm of the butt. Although in the case of this brand visible ventilation holes could be observed
close to the butt the tipping paper over the remainder of the butt also provided some ventilation to
the smoke so it was necessary to ensure that the same level of occlusion was provided. It was
notable that this was not evident from the PD tests alone. When repeated with equivalent levels
of occlusion the CO, TPM and puff counts were statistically equivalent at the 95% level.
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Conclusions
The 100% vent blocking device shows statistical equivalence with taping methods at the 95%
confidence level. The use of holders was significantly faster than the alternative method, taping.
There was no consistent statistical evidence to show that the repeatability was improved by using
holders for 100% occlusion.
References
[1] Determination of “Tar”, Nicotine and Carbon Monoxide in mainstream tobacco smoke” –
Health Canada 1999 T-115
[2] ISO3308:1991 “Routine analytical cigarette smoking machine – definitions and standard
conditions” 1991
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