Note: Descriptions are shown in the official language in which they were submitted.
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VENTILATED SMOKING ARTICLE INCLUDING SORBENT MATERIAL
The present invention relates to a ventilated smoking article incorporating a
filter
wrapper with a sorbent.
Filter cigarettes typically comprise a rod of tobacco cut filler surrounded by
a paper
wrapper and a cylindrical filter aligned in end-to-end relationship with the
wrapped tobacco rod,
with the filter attached to the tobacco rod by tipping paper. In conventional
filter cigarettes, the
filter may consist of a plug of cellulose acetate tow wrapped in porous plug
wrap.
It is common to provide a ventilation zone in a smoking article, typically in
the form of
perforations provided in the tipping paper or the plug wrap, or both. The
ventilation zone allows
air to enter the filter during smoking and the air dilutes the mainstream
smoke coming through
the filter from the burning tobacco rod, thereby reducing the levels of smoke
constituents
delivered to the consumer.
The ventilation zone typically includes perforations provided at one or more
positions
along the filter of the smoking article and some of the perforations can be
inadvertently blocked
during smoking, for example, by the lips or fingers of the consumer. Air is
thereby prevented
from entering the filter and the level of dilution of the mainstream smoke
decreases.
In addition to the inclusion of a ventilation zone, it is also known to
provide a sorbent
material such as activated carbon within the filter of a smoking article as an
additional means to
reduce the level of certain smoke constituents. However, sorbent materials may
adversely
affect the taste of the mainstream smoke in a way that is unfavourable to some
consumers.
It would be desirable to provide a novel filter arrangement for a smoking
article that
substantially maintains the delivery level of certain smoke constituents
whether the ventilation
zone is open or blocked, so that inadvertent covering of the ventilation zone
does not
significantly impact smoke constituent delivery. It would further be desirable
if such a filter
arrangement could be readily manufactured using existing apparatus and
techniques.
According to the invention there is provided a smoking article comprising: a
tobacco rod;
a filter connected to the tobacco rod and comprising one or more filter
segments circumscribed
by a filter wrapper including a sorbent material. The filter includes a
ventilation zone provided
upstream of the sorbent material. The result of this arrangement is that the
level of mainstream
gas phase smoke constituents delivered during smoking of the smoking article
with the
ventilation zone open is within up to 40% of the level of mainstream gas phase
smoke
constituents delivered during smoking of the smoking article with the
ventilation zone blocked.
The ventilation zone refers to the arrangement of perforations or holes that
are provided
on the filter to allow ventilation of the filter and dilution of the
mainstream smoke during
smoking, through the ingress of air through the holes into the filter.
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The ventilation zone is `open' when it is fully uncovered and air is free to
enter the filter
during smoking. The ventilation zone is `blocked' when it is covered or closed
so that air is
prevented from entering the filter through the ventilation zone. With the
present invention, the
level of gas phase mainstream smoke constituents delivered during smoking of
the smoking
article when the ventilation zone is blocked is within up to 40% of the level
of the same
mainstream gas phase smoke constituents delivered during smoking with the
ventilation zone
open. Preferably, the level of gas phase smoke constituents delivered with the
ventilation zone
blocked is within up to 30% of the level delivered with the ventilation zone
open, more
preferably within up to 20% and most preferably within up to 10%.
In the context of the present invention, the term `smoke constituents' is
intended to refer
to the gas phase constituents in the mainstream smoke. In particular, the
smoke constituents
referred to herein are gas phase carbonyl compounds, including aldehyde and
ketone
compounds.
For example, the gas phase constituents may include one or more of
formaldehyde, acetaldehyde, acetone and acrolein.
For the purposes of the present invention, the level of mainstream gas phase
smoke
constituents delivered during smoking of a smoking article according to the
invention with the
ventilation zone open may be determined by smoking the smoking article under
ISO conditions
(35m1 puffs lasting 2 seconds each, every 60 seconds). In the ISO test method,
the smoking
article is smoked with the ventilation zone fully uncovered. For the purposes
of the present
invention, the level of mainstream gas phase smoke constituents is normalised
to nicotine
delivery, so that the level is expressed per mg of nicotine.
The level of mainstream gas phase smoke constituents delivered during smoking
of a
smoking article according to the present invention with the ventilation zone
blocked may be
determined by smoking the smoking article in a Health Canada test method (55m1
puffs lasting
2 seconds each, every 30 seconds). In the Health Canada test method, the
tipping paper is
covered by an air impermeable film or tape so that air cannot enter the filter
through the
ventilation zone and the dilution of the mainstream smoke is approximately 0%.
As above, for
the purposes of the present invention, the level of mainstream smoke
constituents is normalised
to nicotine delivery, so that the level is expressed per mg of nicotine.
The level of gas phase smoke constituents in the mainstream smoke is
determined as
an average for a sample of 20 smoking articles with the ventilation zone open
and 20 smoking
articles with the ventilation zone blocked. The level of smoke constituents is
measured as the
aggregate amount of carbonyl compounds.
The present invention provides an effective way of maintaining a relatively
constant
delivery of gas phase smoke constituents in a ventilated smoking article,
regardless of whether
the ventilation zone is open or blocked.
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In the present invention, the sorbent material is positioned within the filter
of smoking
articles such that under normal smoking conditions with the ventilation zone
open, the dilution of
the mainstream smoke by air entering the filter through the ventilation zone
will be the main
mechanism by which the level of smoke constituents in the mainstream smoke is
reduced. The
ventilation air will provide an air cushion that will isolate much of the
mainstream smoke from
the sorbent. As such, the sorbent will have a minimal effect on the level of
gas phase smoke
constituents and the flavour of the mainstream smoke when the ventilation zone
is open.
In contrast, when the ventilation zone is fully blocked and air is prevented
from entering
the filter and diluting the mainstream smoke, the flow of the mainstream smoke
through the filter
changes so that the smoke passes over the sorbent and certain gas phase smoke
constituents
are adsorbed or adsorbed by the sorbent. In this case, the sorption of smoke
constituents will
be the main mechanism by which the level of smoke constituents in the
mainstream smoke is
reduced.
In some cases, when the ventilation zone is partly blocked, the reduction of
smoke
constituents in the mainstream smoke will be achieved both through the
dilution of the
mainstream smoke and by the sorbent. The arrangement of the sorbent and
ventilation zone is
such that there is a balance between the reduction of gas phase smoke
constituents by dilution
and the reduction of the same gas phase smoke constituents by the sorbent,
wherein the
balance will automatically shift depending on the degree to which the
ventilation zone is
blocked. If the level of dilution decreases as a result of blocking of the
ventilation zone, the
sorption of smoke constituents by the sorbent material will increase to
compensate for the lower
dilution. The total level of smoke constituents can therefore be maintained
with as little variation
as possible, irrespective of whether the ventilation zone is open, partially
blocked, or fully
blocked.
The balance between the level of dilution of the mainstream smoke achieved by
the
ventilation zone and the sorption of mainstream smoke constituents by the
sorbent at the
surface of the filter wrapper can be controlled by adjusting parameters of the
filter, including but
not limited to the positioning and distribution of the ventilation zone, the
level of dilution
achieved by the ventilation zone, and the positioning, distribution and amount
of sorbent
provided, as described in more detail below. For example, the amount and
position of the
ventilation zone and the amount and position of the sorbent can be adjusted
such that the
delivery of gas phase smoke constituents is the same whether the ventilation
zone is open or
blocked.
In the filters of smoking articles according to the invention, the ventilation
zone may be
provided upstream of most or all of the sorbent material. With this
arrangement, the flow of the
mainstream smoke within the filter changes depending on how much air is drawn
through the
filter from the ventilation zone. With the ventilation zone open, the
ventilated air is typically
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drawn through the filter on the outside of the filter material, constraining
the flow of the
mainstream smoke towards the centre of the filter. The air drawn through the
ventilation zone
therefore provides an outer, concentric layer which effectively separates and
shields the
mainstream smoke from the sorbent that is included in the filter wrapper. In
this way, the
mainstream smoke does not significantly come into contact with the sorbent.
During normal
smoking of the smoking article, the sorbent will therefore have a minimal
effect on the
mainstream smoke.
The ventilation is 'upstream' of the sorbent material, meaning that the
ventilation is
provided further from the mouth end of the smoking article than the sorbent.
During smoking,
the mainstream smoke is drawn through the smoking article from an upstream
end, closest to
the burning end of the tobacco rod, to a downstream end, at the mouth end of
the filter. The
mainstream smoke will therefore pass the ventilation zone first, before
reaching the sorbent in
the filter wrapper.
Preferably, the ventilation zone is in the form of one or more rows of
perforations
extending circumferentially around the filter. In certain embodiments, a
plurality of rows of
perforations may be provided at spaced apart locations along the filter, for
example at least
5mm from one another, or at least lOmm from one another. This arrangement
means that air is
admitted into the filter at different positions during smoking and may help to
maintain a
consistent layer of air between the mainstream smoke and the sorbent along the
full length of
the sorbent. In such a case, the most upstream ventilation zone may be
upstream of all or most
of the sorbent.
When the ventilation zone is blocked, the volume of air entering the filter
will be reduced
and in the case where the ventilation zone is fully blocked, substantially no
air will enter the
filter. In the absence of the layer of air towards the outside of the filter,
the mainstream smoke
will no longer be confined to the central portion of the filter and the smoke
flowing through the
outside of the filter will come into contact with the sorbent included in the
filter wrapper. The
smaller the volume of air that is drawn through the filter, the larger the
volume of mainstream
smoke that will come into contact with the sorbent and the sorbent will remove
an increased
amount of smoke constituents.
In cases where the ventilation zone is partially blocked, the flow of air and
smoke
through the filter will be a combination of the two flow patterns, depending
upon the relative
position of the blocked ventilation zone on the filter and the extent of the
blockage. For
example, if part of the ventilation zone towards the mouth end of the filter
were blocked but the
upstream ventilation zone remained open, the mainstream smoke may initially be
separated
from the sorbent by a layer of air at the outside of the filter but the
ventilated air and the smoke
may mix towards the mouth end of the filter, causing more of the smoke to come
into contact
with the sorbent.
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Preferably, the ventilation zone provides between 10% and 80% dilution of the
mainstream smoke, wherein the 'dilution' refers to the percentage by volume of
air that is
included in the smoke delivered to the consumer from the mouth end of the
filter with the
ventilation zone completely open. More preferably, the ventilation zone
provides between 30%
and 70% dilution of the mainstream smoke, more preferably between 50% and 80%.
The level
of ventilation or dilution achieved by the ventilation zone can be determined
using ISO test
method 9512:2002.
The ventilation level can advantageously be adjusted to control the thickness
of the
concentric air layer flowing through the outer concentric region of the filter
and separating the
mainstream smoke from the sorbent. The thicker the layer of air at the outside
of the filter, the
greater will be the effect of the air layer at shielding the mainstream smoke
from the sorbent.
This will also reduce the effect the sorbent will have on the flavour of the
smoke delivered to the
consumer when smoking with the ventilation zone open. As another alternative,
the level of
ventilation through the ventilation zone may be set and the amount of sorbent
may be adjusted
so that the delivery of gas phase smoke constituents is similar whether the
ventilation zone is
open or blocked.
Preferably, the most upstream portion of the ventilation zone is provided
between 20 mm
and 30 mm from the mouth end of the smoking article. Preferably, the most
upstream portion of
the ventilation zone is provided at least 2 mm from the rod end of the filter,
where the filter abuts
the rod of tobacco. This positioning of the ventilation zone away from the
mouth end of the filter
and towards the rod of tobacco advantageously increases the available area in
which the
sorbent may be placed downstream of the ventilation zone.
The ventilation zone is provided upstream of all, or substantially all of the
sorbent
material. Whilst the ventilation zone is preferably provided upstream of all
of the sorbent
material, the skilled person will appreciate that the desired effect of the
present invention can be
achieved where the majority of the sorbent is downstream of the ventilation
zone, even if a
small proportion is provided at the position of the ventilation zone, or
upstream of the ventilation
zone. Preferably, the ventilation zone is provided upstream of at least 80% of
the sorbent.
The sorbent material may be formed of any suitable adsorbent or absorbent
material. A
variety of sorbents for use in smoking articles would be known to the skilled
person. Suitable
sorbents include but are not limited to activated carbon, zeolites,
sepiolites, alumina, molecular
sieves and combinations thereof. In particularly preferred embodiments, the
sorbent is
activated carbon.
In preferred embodiments, the filter wrapper of smoking articles according to
the
invention comprises a layer of sorbent applied over an area of a surface of
the filter wrapper.
Preferably, the amount of sorbent in the layer is at least about 20 mg. The
amount of sorbent is
preferably up to about 120 mg, more preferably up to about 100 mg, more
preferably up to
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about 60 mg. Particularly preferably, the amount of sorbent is between about
20 mg and about
120 mg, more preferably between about 40 mg and about 60 mg.
The sorbent material is preferably provided in the form of a particulate or
granular
sorbent, which is preferably applied to a layer of adhesive or binder on the
surface of the filter
wrapper. In alternative embodiments, the sorbent may be provided as a separate
layer located
at the surface of the filter wrapper. In other alternative embodiments, the
sorbent material may
be applied as a separate layer to the outer surface of a filter segment and
the filter wrapper may
be wrapped over the sorbent layer to bring the surface of the filter wrapper
into contact with the
sorbent.
lo In addition or as an alternative to the provision of sorbent material in
a layer at the
surface of the filter wrapper, a sorbent material may be incorporated towards
the outside of the
filter material itself. For example, where the filter comprises a plug of
fibrous filter material such
as cellulose acetate tow, a particulate sorbent material may be provided in a
concentric, outer
layer of the filter tow, for example a concentric, outer layer that is less
than lmm thick. The
sorbent may be provided uniformly in a concentric outer layer of the filter
tow, or there may be a
concentric gradient of sorbent within the filter, wherein the proportion of
sorbent in the filter tow
increases towards the outside of the filter.
In addition or as an alternative to the arrangements of sorbent described
above, a
sorbent may be incorporated into the sheet material forming the filter
wrapper, for example, the
sorbent may be incorporated into a paper material during production of the
material.
Where the sorbent material is on a surface of the filter wrapper, the sorbent
material
preferably covers at least 50% of the outer or inner surface of the filter
wrapper, more preferably
at least 60%. The sorbent material may be provided within a single area, or
may be provided in
a plurality of areas over the surface of the filter wrapper, for example, in
the form of a pattern
applied to the surface of the filter wrapper.
The sorbent material is preferably provided on the inner surface of the filter
wrapper,
wherein the 'inner' surface refers to the radially inner surface of the
wrapper, which is closest to
the filter segment. However, in certain alternative embodiments it may be
effective to provide
the sorbent on the outer surface of the wrapper in addition to or as an
alternative to sorbent on
the inner surface, provided the mainstream smoke will still be brought into
contact with the
sorbent during smoking. For example, where the filter wrapper is highly porous
or air
permeable, the sorbent may be provided on either or both of the inner and
outer surfaces since
the mainstream smoke will be in contact with both surfaces during smoking.
In certain preferred embodiments of the present invention, the filter wrapper
to which the
sorbent is applied is a plug wrap circumscribing the filter along at least a
part of its length. The
sorbent may be applied to an inner layer of plug wrap, the inner surface of
which is in contact
with the underlying filter material.
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In some cases, the filter is wrapped with a second layer of plug wrap, for
example a
layer of plug wrap that combines the different segments of a multi-component
filter.
Alternatively or in addition to the sorbent on the inner layer of plug wrap,
sorbent material may
be applied to this second layer of plug wrap, which overlies one or more inner
layers of an air
permeable plug wrap. The sorbent material may be applied to an area of the
inner surface of
the second layer of plug wrap. Alternatively or in addition, the sorbent
material may be applied
to the outer surface of the second layer of plug wrap, in particular where the
second layer of
plug wrap is formed of a substantially air permeable sheet material so that
the mainstream
smoke will readily permeate through the second layer of plug wrap to come into
contact with the
sorbent.
In other preferred embodiments of the present invention, the filter wrapper to
which the
sorbent is applied is a tipping wrapper, such as a tipping paper,
circumscribing the filter and
connecting the filter to the tobacco rod. Where the sorbent material is
provided on the tipping
wrapper, the material should be applied to the inner surface of the tipping
wrapper so that it is
not exposed at the outside of the filter.
The filter of smoking articles according to the present invention may include
a single filter
segment. Alternatively, the filter may comprise two or more filter segments in
axial alignment
with each other. The filter segment or segments may take a variety of forms
and suitable filter
segments would be known to the skilled person. Where two or more filter
segments are
included, the filter segments may be of the same construction and materials as
each other, or
may have a different construction, or contain different filtration material or
additives. Preferably,
the filter segment or segments are each formed of a plug of fibrous filtration
material, such as
cellulose acetate tow or paper, and wrapped with a plug wrap.
One or more of the filter segments may include a particulate material. The
particulate
material is preferably incorporated in an upstream filter segment, for
example, in a rod end filter
segment.
The particulate material may be dispersed through a plug of fibrous filtration
material,
such as cellulose acetate or paper. A filter plasticiser may be applied to the
fibrous filtration
material in a conventional manner, by spraying it onto the separated fibres,
preferably before
applying the particulate material to the filtration material. Alternatively or
in addition, the filter
may include a filter segment with a hollow cavity at least partially filled
with a particulate
material. In such cases, the hollow cavity is preferably provided between two
plugs of a
filtration material.
The particulate material incorporated into the filter may include at least one
sorbent
material, such as those indicated above for inclusion in the filter wrapper.
Where a sorbent is
incorporated within the filter, the amount of sorbent within the filter should
be less than the
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amount of sorbent included in the filter wrapper so that the performance
characteristics of the
filter can be maintained.
Additionally or as an alternative, the particulate material incorporated into
the filter may
include at least one flavourant material. For example, the particulate
material may include
particles of a sorbent or cellulosic material loaded with a liquid flavourant,
such as menthol.
Alternatively, the particulate material may comprise particles of plant
material. The plant
material may be in the form of plant leaf, as described in EP-A-1,958,523. For
example, the
filter segment may include leaf from tobacco, green tea, mint, such as
peppermint or spearmint,
laurel, eucalyptus, basil, sage, verbena and tarragon. The plant material may
alternatively be in
the form of a seed, root, bark or flower, such as those typically used as
spices.
Alternatively, one or more of the filter segments may have a liquid flavourant
such as
menthol applied directly to the filtration material.
Preferably, the overall length of smoking articles according to the invention
is between
70 mm and about 128 mm, for example about 84 mm.
Preferably, the external diameter of smoking articles according to the
invention is
between about 5 mm and about 8.5 mm, more preferably about 7.9 mm.
Preferably, the overall length of the filters of smoking articles according to
the invention
is between about 18 mm and about 36 mm, more preferably about 27 mm.
The smoking articles of the present invention comprise a rod of tobacco
material, which
is attached to the filter by a tipping wrapper. The rod of tobacco material
may include cut
tobacco taken from one or more types of tobacco leaf, expanded tobacco,
reconstituted
tobacco, or combinations thereof.
The invention will now be further described by way of example only with
reference to the
accompanying drawings in which:
Figure 1 shows a perspective view of a smoking article according to the
invention, with
the filter unwrapped;
Figure 2 shows a side view of the smoking article of Figure 1, with a
schematic
representation of the flow of air and smoke through the filter when the
ventilation zone is open;
and
Figure 3 shows a side view of the smoking article of Figure 1, with a
schematic
representation of the flow of smoke through the filter when the ventilation
zone is fully blocked.
The filter cigarette 10 shown in Figure 1 comprises a wrapped rod 12 of
tobacco cut
filler, which is attached to an axially aligned filter 14. The tobacco rod 12
is wrapped with a
cigarette paper (not shown). The filter 14 comprises a single segment 16,
which is formed of a
plug of cellulose acetate tow. The filter segment 16 is wrapped with a plug
wrap 18 which
circumscribes the entire length of the filter 14.
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The plug wrap 18 is formed of a sheet of an air permeable paper material and
includes a
sorbent layer 20 covering an area corresponding to approximately 50% of the
inner surface of
the plug wrap 18. The sorbent layer 20 is formed of a substantially evenly
distributed layer of
around 50 mg of particulate activated carbon, which has been affixed to the
inner surface of the
plug wrap 18 by a suitable adhesive. In the assembled filter, the sorbent
layer 20 extends
circumferentially around the filter segment 16 and is in contact with the
outer surface of the filter
segment 16.
The wrapped tobacco rod 12 and the wrapped filter 14 are joined to each other
by an
outer tipping wrapper 22, which circumscribes the entire length of the filter
14 and an adjacent
portion of the tobacco rod 12, and overlies the plug wrap 16. The tipping
wrapper 22 is formed
of a tipping paper which has been provided with ventilation zone comprising a
row of
perforations 24 extending circumferentially around the filter 14. The row of
perforations 24 is
positioned on the filter at the rod end of the filter segment 16, adjacent the
interface between
the filter 14 and the tobacco rod 12. The entire area of the sorbent layer 20
is downstream of
the row of perforations 24. With the perforations open, the ventilation zone
provides about 60%
dilution of the mainstream smoke during smoking.
During normal smoking of the filter cigarette 10, the perforations will be
fully uncovered
and as shown schematically in Figure 2, air will be admitted into the filter
14 through the
perforations in the tipping wrapper 22. In Figure 2, the air flow is indicated
by the hollow arrows
whilst the mainstream smoke flow is indicated by the shaded arrows. As shown,
the air will be
drawn along through the filter 14 towards the mouth end of the filter 14 and
will form a
concentric air layer 26 around the outside of the filter segment 16. The
mainstream smoke will
be drawn from the tobacco rod and the presence of the air layer 26 forces the
mainstream
smoke towards the centre of the filter segment 16 so that the mainstream smoke
is separated
from the inner surface of the plug wrap 18 by the air layer 26. This means
that during smoking
with the perforations 24 fully open, contact will be limited between the
mainstream smoke and
the activated carbon in the sorbent layer 20 on the inner surface of the plug
wrap 18. As such,
the presence of the sorbent layer 20 will have a negligible effect on the
levels of the gas phase
constituents in the mainstream smoke. The air flowing into the filter 14 will,
however, dilute the
mainstream smoke thereby reducing the level of gas phase constituents in the
smoke received
by the consumer by around 60%.
The positioning of the row of perforations 24 upstream of the entire sorbent
layer 20
ensures that the mainstream smoke is directed away from the outside of the
filter segment 16
into the centre of the filter before the mainstream smoke reaches the part of
the filter segment at
which the sorbent layer 20 starts.
Figure 3 illustrates the condition where all of the perforations 24 are fully
covered so that
no air is admitted to the filter 14 during smoking. Under these conditions,
there is no dilution of
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the mainstream smoke in the filter and therefore no reduction of the gas phase
constituents as a
result of the ventilation zone. As shown schematically by the shaded arrows in
Figure 3, in the
absence of the air layer 26 the mainstream smoke is not constrained to the
centre of the filter
segment 16 and can be drawn through the full cross section of the filter
segment 16. Unlike in
the situation shown in Figure 2, the mainstream smoke therefore comes into
contact with the
sorbent layer 20 on the inner surface of the plug wrap 18 as the smoke is
drawn through the
filter 14. The activated carbon in the sorbent layer 20 adsorbs certain gas
phase constituents
from the mainstream smoke and the total level of these constituents in the
smoke delivered to
the consumer is therefore reduced.
The level of the gas phase constituents (carbonyl compounds) in the mainstream
smoke
under the conditions shown in Figure 3 is within up to 40% of the level of the
same gas phase
constituents as a result of the dilution under the conditions shown in Figure
2.
In reality, during smoking the consumer is unlikely to fully block all of the
perforations 24
in the tipping paper 22 and the conditions illustrated in Figure 3 are
therefore only likely to be
brought about during an experimental Health Canada smoking test. The consumer
may,
however, inadvertently block some of the perforations 24, for example, by
placing their fingers
around the filter in the region of the ventilation zone, so that air cannot be
admitted into the filter
14 through the perforations covered by the fingers. In this case, the
conditions will be between
the two examples shown in Figures 2 and 3, wherein the air layer 26 does not
extend all around
the filter 14 and the mainstream smoke will flow into contact with the sorbent
layer 20 in certain
places.
Due to the partial blocking of the perforations 24, the volume of air admitted
to the filter
14 will decrease and the dilution of the mainstream smoke will also decrease
so that the
reduction in the levels of gas phase constituents as a result of dilution will
be less. However,
the contact of the mainstream smoke with the activated carbon in the sorbent
layer 20 will
increase the reduction of the gas phase constituents by the sorbent so that
the overall level of
the gas phase constituents is still within up to 40% of the level under the
conditions shown in
Figures 2 and 3.
It can therefore be seen that the overall level of gas phase constituents in
the
mainstream smoke as a result of the combination of the dilution and the
sorbent layer 20
remains relatively consistent whether the perforations 24 are open, partially
blocked or fully
blocked.
Whilst in the example described above and shown in the figures, the sorbent
layer is
provided on the inner surface of the plug wrap, it will be appreciated that
different arrangements
of the sorbent layer on the plug wrap and/or the tipping wrapper could be
provided with the
same effect on the reduction of the gas phase constituents of the mainstream
smoke, as
described above.
