Note: Descriptions are shown in the official language in which they were submitted.
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Reduction of Ozone in an Enclosed Environment
This invention relates to the reduction of ozone in an
enclosed environment.
The rising number of asthma sufferers in the Western
World and in particular in the United Kingdom is a matter
of great concern and much research has been done to
understand both the causes of the disease and the
mechanisms which trigger the onset of an attack.
It is known from published papers by RB Devlin et al
("Health Effects of Ozone", Science and Medicine, May/June
1997, pages 8 to 17) and by N A Molfino et al ("Effect of
Low Concentrations of Ozone on Inhaled Allergen Responses
in Asthmatic Subjects", The Lancet, Volume 338, No. 8761,
27 July 1991, pages 199 to 203) that relatively low levels
of ozone, similar to those commonly occurring in urban
areas, can increase the likelihood of asthma attacks.
Ozone occurs naturally and can for example be caused
by thunder storms. Ozone is also created by ultraviolet
light. Further, in an office environment levels of ozone
can rise significantly due to the ozone produced by
electrostatic printing equipment such as laser printers and
photocopiers.
The problem of reducing the level of ozone produced by
apparatus such as a photocopier or laser printer has been
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addressed in US 4,853,735. It has been recognised that
such devices are a principle source of ozone in an office
environment and thus this document attempts to deal with
the problem by reducing the level of ozone near the source
i.e. within the apparatus. In order to achieve this a
volatile ozone removing agent comprising a mixture of a
terpenoid and a glycol family material is used. An ozone
removing device is located within the photocopier machine
and is designed to provide a controlled flow rate of ozone
removing agent. With this arrangement, there are several
disadvantages. Firstly the location of the ozone removing
agent within the confines of the photocopier means that it
will be subject to temperature ranges well outside the
normal range of room temperatures and so the evaporation
rates will vary accordingly. Another difficulty is that
the ozone removing device is a fixture to the photocopier
and so will tend to be regarded as a replaceable item for
the photocopier, which will require installation, and the
device will be priced accordingly. Furthermore, the device
requires the use of glycol which is a corrosive material.
In addition, ozone is a naturally unstable compound and so,
outside working hours, the ozone levels in a room will fall
to a baseline level, and thus any evaporation of ozone
reducing agent outside working hours is effectively wasted.
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US Patent 5,567,416 discloses a slow-volatizing
terpenoid composition comprising a mixture of a terpenoid
and an anti-oxidant absorbed into a polymeric network
material. There are several difficulties associated with
this proposal; the substance involved has a relatively low
boiling point and uses an additive to raise the flash point
of the composition. The additive is
dichloropentafluoropropane (HCFC225) which is thought by
some to be environmentally undesirable. Furthermore the
composition includes an anti-oxidant which is intended to
prevent oxidation of the limonene. Since ozone is a
powerful oxidizing agent, it is believed that this anti-
oxidant may inhibit the reaction of the terpene with ozone.
US Patent 5,256,377 describes an ozone removing device
which again is primarily for use in photocopiers. A
terpenoid is absorbed onto a support material and subjected
to forced ventilation by means of a fan at the outlet of a
photocopier.
Japanese Patent Documents JP 1310366, JP 2090184 and
JP 62155927 each disclose arrangements in which an ozone
removing device is located in or adjacent the exhaust duct
of a photocopier.
Accordingly, it is an aim of this invention to provide
a passive method and apparatus for controlling the level of
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ozone in a room or other generally enclosed environment
which does not rely on heating or forced ventilation and
furthermore which provides a controlled release of ozone
reducing agent at a rate commensurate with maintaining the
ozone levels in a room housing a photocopier and/or a laser
printer at acceptable levels, without requiring the use of
potentially harmful additives, so as to make effective use
of the ozone reducing agent to provide an extended ozone-
reducing effect.
Accordingly, in one aspect, this invention provides a
method of reducing the level of ozone in a generally
enclosed environment, which comprises releasing vapour from
a terpenoid or a mixture of terpenoids into the environment
at a controlled rate.
In studies conducted by the Applicants it has been
found that a useful control effect is achieved by releasing
the terpenoid vapour at a rate of between 40 and 120mg per
hour, more preferably between 60 and 100mg per hour, and
ideally about 80mg per hour. The Applicants have
determined that a room may be dosed with terpenoid
compounds at a required given evaporation rate by careful
balancing of the emission characteristics of the support
(e. g. void volume, pore size, particulate size etc.) with
the evaporation characteristics of the terpenoid compound
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(determined by, e.g. the boiling point temperature) and the
amount of terpenoid to be stored. Thus in one preferred
example linalool is impregnated into an emission element of
Vyon E grade material, and, for the size of emission
5 element used an emission rate of about 80 mg/hour is
achieved. More volatile compounds (i.e. with lower boiling
points) would need to be used with a less emissive
material.
It is preferred for said terpenoid vapour to be
released by evaporation from an emission element of
absorbent material. The evaporation preferably takes place
at normal room temperature (17° C to 25° C) (i.e. no heating
is required), such that the evaporation rate, and thus
working life of the emission element can be predicted.
Likewise evaporation and permeation of the vapour
throughout the generally enclosed environment preferably
occurs in natural, unforced ventilation (i.e. no fan or
confining duct is used).
Preferably said emission element is located in a
container configurable between an open position, in which
the element is exposed to the ambient atmosphere and a
closed position in which said element is generally enclosed
within a housing.
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Preferably the emission element comprises a porous
synthetic polymer structure. The polymer lattice may
conveniently be produced by moulding and/or sintering a
starting material comprising a synthetic thermo-plastic
polymer in particulate form.
In one embodiment, the starting material is a high
density polyethylene in which at least 80o by weight of the
particles have a particle size within the range of from 1
to 500 micron.
Naturally the size and weight of the emission element
depend at least partly on the size of the room to be
treated, the volatility of the absorbed liquid and the
porosity of the element. In one example said emission
element, before absorption of said terpenoid, may typically
weigh from 5 to 15 grams. The emission element preferably
contains between 10 and 20 grams of terpenoid liquid, and
ideally about 15 grams thereof.
The void volume of the emission element may
conveniently lie in the range of from 25o to 70o and more
preferably between 30o and 550. In a particular example,
the average pore size of the emission element is between 10
and 100 microns.
Preferably the or each terpenoid comprises a terpene
or a carotenoid. At least one of the terpenoid compounds
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preferably comprises a compound extracted from a plant, or
a synthesised compound corresponding to a constituent of a
plant extract. Plant extracts that we have found to be
suitable are lavender oil, orange oil, grapefruit oil, lime
oil, myrtle oil, coriander oil, tea tree oil, elecampane
oil, juniper oil, dill oil, lemon oil, elemi oil, spanish
sage oil, cypress oil, pine needle oil, lemon balm
(melissa) oil, nutmeg oil, ylang ylang oil, basil oil,
grapeseed oil, whilst suitable natural or synthesised
compounds comprise a phellandrene, a humulene, a terpinene,
limonene, a pinene, (3 caryophyllene, linalool, linalyl
acetate, and myrcene.
To enhance safety without requiring the use of
modifiers etc., the flash point of the terpenoid compound
is preferably greater than 60° C.
Of the compounds set out above we have found linalool
to be particularly effective in terms of reaction with
ozone and a sustained evaporation rate.
In another aspect, this invention provides the use of
at least one of lavender oil, orange oil, grapefruit oil,
lime oil, myrtle oil, coriander oil, tea tree oil,
elecampane oil, juniper oil, dill oil, lemon oil, elemi
oil, spanish sage oil, cypress oil, pine needle oil, lemon
balm (melissa) oil, nutmeg oil, ylang ylang oil, basil oil,
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grapeseed oil, a phellandrine, a, humulene, a, terpinene,
limonene, a pinene, (3 caryophyllene, linalool, linalyl
acetate, or myrcene for the removal of ozone in a generally
enclosed environment.
In another aspect, this invention provides apparatus
for removing ozone in a generally enclosed environment,
said apparatus comprising an emission element of absorbent
material impregnated with at least one terpenoid compound
located within a container which in use allows free
circulation of vapour into said environment.
Preferably said container is reconfigurable between an
open operational configuration, in which vapour evaporating
from said emission element may dissipate into said
environment, and a closed configuration in which said
emission element is enclosed.
Advantageously, said container comprises an inner
housing having perforate walls, said inner housing being
movably mounted with respect to an outer housing.
Preferably said emission element comprises a porous polymer
substrate impregnated with a terpenoid compound. Said
terpenoid compound may advantageously comprise linalool,
preferably without additives. Preferably said emission
element contains between 10 and 20 grams of linalool.
Preferably said emission element has a void volume of
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between 25° and 70o and an average pore size of between 10
and 100 microns.
Whilst the invention has been described above it
extends to any inventive combination of the features set
out above or in the following description.
The invention may be performed in various ways, and an
embodiment thereof and certain test results will now be
described in detail, reference being made to the
accompanying drawings, in which:-
Figure 1 is a front plan view of an ozone removing
apparatus in accordance with the invention, in an open
position;
Figure 2 is a side view, taken on the left hand side
of the apparatus of Figure 1;
Figure 3 is a graph showing the decay of the
concentration of ozone in a closed environment (i)
naturally and (ii) when an ozone reducing device in
accordance with this invention is present, and
Figure 4(a) to 4(d) are comparative graphs showing the
build up of ozone in a closed environment containing an
ozone generator (i) with natural decay only (ii) with a
first example of this invention and (iii) with a second
example of this invention, after 72, 96, 120 and 168 hours
respectively.
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Referring to Figures 1 and 2, a dispenser comprises a
perforated housing 10 containing an emission disk or
element 12 made of a sheet of an absorbent porous polymer
lattice structure available under the Trade Name Vyon Grade
5 E from Porvair Zimited, Norfolk, UK. The disk was
approximately 90mm in diameter, 5mm thick, and weighed
approximately 10 grams. The emission element 12 was left
to stand in a dish of a terpenoid (in this example
linalool) until saturated. The emission element took up
10 about 15 grams of linalool. The porosity of the support
was selected having regard to the volatility of the
linalool so that, under normal room temperature conditions,
with natural ventilation, the emission element emitted
about 80mg of linalool per hour. This gave a theoretical
maximum life of 187.5 hours which is equivalent to
approximately one month of working hours in a typical
office room containing a photocopier.
The perforated housing 10 is pivotally mounted within
an outer, imperforate housing 14 having a pivotal
attachment, so that the apparatus can be moved between an
open position (as shown in Figure 1) and a closed position
in which the container is enclosed substantially wholly
within the housing 14 thus preventing release of the
linalool.
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Referring now to Figure 3, this is a graph showing the
natural decay rate of ozone and the decay rate with a
product in accordance with the invention. In this instance
the product included a rectangular emission element of Vyon
F material, of 90mm x 70mm and 9.75mm thickness,
impregnated with about 15 grams of linalool. It will be
seen that the time taken for the ozone concentration to
reduce naturally to 50 ppb is over 1000 seconds, whereas
with the example of the invention the ozone concentration
reduces to 50 ppb in about 260 seconds.
Referring now to Figures 4a to 4d, these are graphs
showing the ozone concentration or build up in a closed
test environment when an ozone generator is turned on. On
each graph there are three traces; the ozone concentration
without any ozone removing agent, and the ozone
concentration with two examples of the invention (Vyon E#1
and Vyon E#2). In addition to this, the sequence of
Figures 4(a) to 4(d) show the characteristics of two
examples of the invention after 72, 96, 120 and 168 hours
respectively. The examples of the invention comprised Vyon
E grade disks 90mm in diameter and 4.75 mm thick, with an
original impregnation of about l5gms of linalool. These
graphs show individually that the examples of the invention
maintain the ozone concentration at a peak level of below
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about 75 ppb and generally at about 50 ppb or lower,
whereas without the ozone-removing devices the ozone
concentration would reach over 200 ppb. The graphs as a
set show that the examples of the invention retain their
ozone-removing effect substantially unchanged for at least
168 hours. Assuming that the devices are closed outside
working hours and that there is no significant evaporation
when closed, this means that the examples will continue to
be highly effective for at least 21 working days.
As noted above the apparatus emits linalool vapour at
a rate of about 80mg per hour, (when the device is open).
This emission rate is substantially constant over the life
of the pad. Our studies have shown that, in a typical
office environment including a photocopier and a laser jet,
about lOmg of ozone may be produced per hour. Given the
relative molecular weights of linalool and ozone, 32mg of
linalool per hour would be required, assuming that each
molecule of linalool reacted with an ozone molecule. In
practice an excess of linalool is required and for this
purpose a factor of between 2 and 3 has been found to work
reasonably well. Accordingly it has been found that an
evaporation rate of linalool of between 60 to 100mg per
hour provides good performance.
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These emission rates, together with the sustained
extended emission life achieved through careful matching of
the properties of the oil with the emission element,
provide a particularly effective solution to the problem of
maintaining low ozone levels in an office environment.
Furthermore, the active agent in the material can be
derived from natural sources or be a synthetic derivation
thereof, and so is environmentally friendly without
requiring additives, which may themselves be seen as
environmentally unfriendly, or other substances which may
add to the material or manufacturing cost of the device.
Whilst the above embodiment uses linalool on a
absorbent pad of Vyon E material, it will of course be
appreciated that other terpenoids may be used with other
emission elements.
The tables below illustrate the terpenoid compounds
which have been tested for their effectiveness in carrying
out the present invention. In Table 1, the compounds are
shown ranked in order of reactivity, showing the time taken
to reduce the concentration of ozone in a standard test
atmosphere (100ppb ozone) to 500 of the standard
concentration (t100-50) and to 200 of the standard
concentration (t100-20).
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The tests were carried out with a grade of Vyon
material which emitted at a higher rate than Vyon 'E',
initially impregnated with 5m1 of linalool, but the results
are a good illustration of the relative performance of the
substances.
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TABLE 1
Essential Oil and Chemical RcactivitX
essential Oil/Chemicalt100-50 (sec) t100-20 (sec)
Tangerine 112 226
Myrcene 122 261
Mandarin 122 28U
Limonene 131 292
Fir needle 132 336
Melissa 163 407
Carrot seed 169 404
Linalool 185 387
Bay 195 526
Dill seed 195 S87
Myrtle 200 506
Fennel 201 449
Ravensara 239 567
May Chang 250 524
Inula 260 544
Petitgrain 265 647
Cajcput 276 723
(3-pinene 288 653
Coriander 292 571
Manuka 320 756
Clary Sage 320 714
Ho Wood 325 866
Eucalyptus 328 664
Spearmint 329 776
Citronella 330 > 1000
(3-Caryophyllene 344 645
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TABLE 1 (cont.l)
Sage 350 >1000
1'eppcnnint 352 730
Ginger 3S4 814
Niaouli 359 741
Lynalyl acetate 375 736
Myrrh 384 839
Palma.rosa 388 892
Spanish sage 392 >1000
Thyme 392 > 1000
Geraniol 399 > l 000
Valerian 407 785
Cardamon 409 992
Oregano 423 954
Patchouli 460 > 1000
Friars Balsam 468 > 1000
Terpineol 474
Nerol 486 >1000
Ciruiamon 503 >1000
Citronellol 530 > 1000
YlangYlangExtra 531 >1000
Geranium 538 > 1000
Ylang Ylang 539 >1000
Cedar Wood 539 >1000
Jasmine S84 >1000
Amyris 628 >I000
Citral 647 > 1000
Soya 667 >1000
Farnesol 669 > 1000
Coconut 673 >1000
Hop Oil 688 >1000
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TABLE 1 (cont.2)
Oleic acid 688 >1000
Cartot tissue 691 > 1000
Almond Oil 731 >1000
Clove bud 738 >1000
1-iypericum 741 > 1000
Hop l;xtract 742 >1000
Calendula 749 > 1000
Borage 768 =1000
Sunflower 771 > 1000
Apricot Kcmal 784 >1000
Rosehip 796 >1000
Grape Seed 808 >1000
Evening Primrose 813 >1000
Clove Stcm 827 >1000
Peach Kernal 831 > 1000
Rapeseed 841 >1000
Teak 844 >1000
Jojoba 915 >1000
4-allyl anisole 925 >1000
Vetiver 934 >1000
Wheatgenn 943 >1000
Avocado 1002 >1000
