WO2006056762A1

WO2006056762A1 - Vapour emanation device

Info

Publication number: WO2006056762A1
Application number: PCT/GB2005/004485
Authority: WO
Inventors: Daniel Jeremy Craven; Benjamin David Hindle
Original assignee: Reckitt Benckiser (Australia) Pty Limited; Reckitt Benckiser (Uk) Limited
Priority date: 2004-11-23
Filing date: 2005-11-23
Publication date: 2006-06-01
Also published as: AU2005308590A1; GB0425744D0; AR055535A1; BRPI0518184A

Abstract

A vapour emanation device (2) comprising a reservoir (4) storing a solution (12), a wick (6) adjacent an aperture (14) open to the atmosphere, the wick (6) being in communication with the solution (12) in the reservoir (4) through a wick seal (20), a first layer (8) and a second layer (10) of material between which the wick (6) is located and sealed, and an insulating layer (18) in contact with the second layer (10) and heated by a heater (16). The aperture (14) is formed in the first layer (8) such that heat radiated by the heater (16) is partially dissipated by the insulating layer (18) to reduce the temperature of the second layer (10) and the wick (6) in the vicinity of the aperture (14) to enable control of the rate of emanation of the solution (12) through the aperture (14) within a predetermined target emanation rate range.

Description

VAPOUR EMANATION DEVICE

Field of the Invention

This invention relates to improvements in vapour emanation devices.

Background to the Invention

In a vapour emanation device that incorporates a wick in contact with a reservoir of solvent containing an insecticide and possibly a fragrance (henceforth described as solution) at a first end and heated at a second end on the other side of a wick seal to vaporise the solution to the atmosphere, it is a common problem to firstly obtain a substantially consistent rate of emanation of the solution and secondly to attain the emanation rate in a target range. At relatively high emanation rates condensation can form on the outside of the device leading to consumers coming in contact with the solution. Whilst at relatively low emanation rates the volume of liquid required in the reservoir, for a product needed to operate for a number of nights, can be so small that it is difficult to determine when the device is full or empty. Furthermore at low emanation rates there may not be enough active released into the air to achieve satisfactory bio-efficacy (bite inhibition).

In order to achieve a substantially consistent emanation rate it is necessary to minimise vacuum effects that build up within the reservoir behind the wick seal. A vacuum can be created by the wicking or capillary action of the solution through the wick within the reservoir which provides an opposing force counteracting the flow of liquid out of the reservoir. Thus the effect created by the vacuum in the reservoir slows or in some cases completely stops the flow of liquid out of the reservoir through the wick.

Each emanation device has a release rate of solution that can be maintained. This rate is determined by operating the device and measuring the mass loss over time. The release rate is simply the rate at which the mass is lost. It is usually measured as milligrams per hour (mg/hr) or grams per hour (g/hr). _The area under a typical release rate curve 22, shown in Figure 1, is the actual mass lost.

The release rate curve 22 shows initially that a large mass of the solution is lost and then approaches an equilibrium which can be described as a release rate limit 24 as time progresses. Therefore a lot of wastage of solution occurs in the period up to time ti. hi order to prevent this wastage, it is desirable to design the refill to have a substantially consistent or steady loss that approaches the release rate limit very quickly such as is exhibited by example curves 26 and 28. This will minimise the loss of solution and make the solution last a lot longer in use.

Furthermore some devices can quickly emanate solution initially and have a release rate limit close to zero, such as curve 23 after time ti. This is unacceptable as the refill still may appear half full but as the release rate is so low it does not give acceptable protection from biting mosquitos.

The present invention seeks to overcome the above-mentioned disadvantages by providing an improved vapour emanation device that takes account of high variability in release rates of solution from vapour emanation devices.

Summary of the Invention

According to a first aspect of the invention there is provided a vapour emanation device comprising: a reservoir storing a solution; a wick adjacent an aperture open to the atmosphere, the wick being in communication with the solution in the reservoir through a wick seal; a first layer and a second layer of material between which the wick is located and sealed; and an insulating layer in contact with the second layer and heated by a heater; the aperture formed in the first layer; such that heat radiated by the heater is partially dissipated by the insulating layer to reduce the temperature of the second layer and the wick in the vicinity of the aperture to enable a control of the rate of emanation of the solution through the aperture within a predetermined target emanation rate range. According to a second aspect of the invention there is provided a vapour emanation device comprising: a reservoir storing a solution; a wick adjacent an aperture open to the atmosphere, the wick being in communication with the solution in the reservoir through a wick seal; a first layer and a second layer of material between which the wick is located and sealed; the aperture formed in the first layer; wherein the aperture is dimensioned to assist with the control of the rate of emanation of the solution through the aperture within a target emanation rate range upon application of heat to the second layer and the wick in the vicinity of the aperture. According to a third aspect of the invention there is provided a vapour emanation device comprising: a reservoir storing a solution; a wick adjacent an aperture open to the atmosphere, the wick being in communication with the solution in the reservoir through a wick seal; a first layer and a second layer of material between which the wick is located and sealed; and the aperture formed in the first layer; wherein the wick has a cross-sectional area dimensioned to assist with the control of the rate of emanation of the solution through the aperture within a target emanation rate range upon application of heat to the second layer and the wick in the vicinity of the aperture.

According to a fourth aspect of the invention there is provided a vapour emanation device comprising: a reservoir storing a solution; a wick adjacent an aperture open to the atmosphere, the wick being in communication with the solution in the reservoir through a wick seal; a first layer and a second layer of material between which the wick is located and sealed; and an insulating layer in contact with the second layer and heated by a heater; the aperture formed in the first layer; such that heat radiated by the heater is partially dissipated by the insulating layer to reduce the temperature of the second layer and the wick in the vicinity of the aperture and a cross-sectional area of the wick is dimensioned to assist with the control of the rate emanation of the solution through the aperture within a predetermined target^" emanation rate range.

The aperture may be dimensioned to enable a controlled rate of emanation of the solution through the aperture within a target emanation rate range upon application of heat to the second layer and the wick in the vicinity of the aperture. The first layer of material may comprise any one of plastics, metal foil or laminates of plastic or metal foil. The material of the first layer may be aPET. The thickness of the first layer may be between 20 microns and 1000 microns, more preferably between 100 microns and 500 microns and most preferably in the order of 250 microns. The second layer of material may comprise any one or more of plastics, metal foils, cellulose or ceramic material. The second layer of material may comprise a laminate of polyester and aPET heat sealed to the first layer. Preferably the thickness of the second layer is between 10 microns and 1000 microns, more preferably between 25 microns and 100 microns and most preferably in the order of 30 microns.

The cross-sectional area of the wick may be altered by varying the thickness of the wick or by varying the width of the wick. Preferably the wick thickness is between

20 microns and 600 microns, more preferably between 100 microns and 300 microns and most preferably between 180 microns and 220 microns. Preferably the wick width is between 0.1 mm and 22 mm, more preferably between 1 mm and 10 mm and most preferably between 5 mm and 10 mm and specifically between 8 mm and 10 mm. The wick may comprise any one of cellulose, plastics or ceramic material.

The aperture may have a diameter between 0.1 mm and 20 mm, more preferably between 1 mm and 10 mm and most preferably between 2 mm and 5mm.

The target emanation rate range may be between 0.1 mg/hr and 50 mg/hr, more preferably between 1 mg/hr and 20 mg/hr and most preferably between 3 mg/hr and 15 mg/hr.

The insulating layer may comprise any one of cellulose, plastics or ceramic material. The thickness of the insulating layer may be between 0.1 mm and 4 mm, more preferably between 1 mm and 3 mm and most preferably between 2 mm and 2.8 mm.

Brief Description of the Drawings

Preferred embodiments of the invention will hereinafter be described, by way of example only, with reference to the drawings, wherein:

Figure 1 is a graph showing a plot of release rate of solution against time for a number of samples;

Figure 2 is a side view of a vapour emanation device according to an embodiment of the invention;

Figures 3 A and 3B respectively show graphs of the weight loss against time and the instantaneous release rate of solution for a number of devices having variously sized apertures; and

Figure 4 is a graph showing the release rate of solution from a number of devices using various wick materials.

Detailed Description of Preferred Embodiments Shown in Figure 2 is a side view of a vapour emanation device 2 having a reservoir 4 and a wick 6 sandwiched between a first layer 8 and a second layer 10. One end of the wick 6 protrudes into the reservoir 4 and is in contact with solution 12 so that a wicking action enables the solution 12 in the reservoir 4 to move along the wick to an area adjacent an aperture 14 so that the solution can be vaporised to the atmosphere under the action of a heater element or heater plate 16. An insulating layer 18 generally is used as a support for the device 2 so that it is easily insertable into an existing heater unit or device containing a heater. The insulating layer is also used to reduce the operating temperature of the device, which assists in slowing the emanation rate of the solution 12. The heater plate 16 may be in direct contact with the insulating layer 18, separated from insulating layer 18 by an intermediate layer or layers, or separated from insulating layer 18 by an air gap. A seal 20 extends transversely across the device 2 to provide adequate sealing around the wick 6 and each of the layers 8 and 10.

The first layer 8 is generally made from plastics, metal foils, or laminates of these. The thickness of the first layer 8 is preferably between 20 microns and 1,000 microns. More preferably, the thickness of the first layer 8 is between 100 microns and 500 microns and most preferably in the order of 250 microns. The preferred embodiment uses amorphous polyethylene terephthalate (aPET) material in the order of 250 microns in thickness.

The second layer 10 is generally made from plastics, metal foils, cellulose, ceramic or a combination of these. The preferred embodiment is MYLAR^® (MYLAR is a registered trademark of Dupont Teijin Films U.S., Limited Partnership) which is heat sealed to the upper layer 8 and then glued to the insulating layer 18 that is in contact with the heater mat 16. MYLAR^® is generally a laminate of polyester with an aPET. The insulating layer 18 also provides protection to the second layer 10 from deliberate puncturing. The thickness of the second layer 10 is preferably between 10 microns and 1,000 microns. More preferably, the thickness of the second layer 10 is between 25 microns and 100 microns and most preferably in the order of 30 microns.

Risk of consumer contact with the solution from the exposed wick at the aperture is minimised by the use of a peelable label 25 covering the aperture on the first layer 8. This label may be made from a variety of plastic, foil or combination laminates with or without adhesive. The preferred embodiment involves the use of a peelable, heat sealable MYLAR^® material which is resistant to the solution and provides a liquid tight seal but can still be removed easily when required.

The target range emanation rate of the solution 12 in reservoir 4 is between 0.1 mg/hr and 50 mg/hr. More preferably between 1 mg/hr and 20 mg/hr and most preferably between 3 mg/hr and 15 mg/hr. This target range and a substantially consistent emanation rate is achieved by a number of features of the device on their own or in combination.

One such feature/aspect of the device 2 that assists in achieving the target range and controls the emanation rate is the inclusion of insulating layer 18. The layer serves four purposes in the device 2. Firstly it protects the reservoir 4 from puncture, secondly it reduces the temperature to an acceptable level for the stability of the MYLAR^® material of layer 10 (MYLAR^® is tolerant to 120°C), thirdly it reduces the temperature at the emanation aperture 14, thus controlling the overall emanation rate and fourthly it allows the device to be held firmly in the heating device. The insulating layer 18 may be a cellulose, plastic or ceramic material.

The material thickness is between 0.1mm - 4mm, more preferably 1.0mm - 3.0mm, most preferably 2.0 - 2.8mm. In the preferred embodiment the material is a pure cellulose mat material of thickness 2.8mm. The maximum thickness of the insulating material must be such that it is able to fit within the existing mat devices on the market throughout the world.

Another such feature/aspect of the device 2 that assists in achieving the target range and controls the emanation rate is the cross sectional area of the wick. This area may be adjusted by changing the thickness or width of the wick 6. The wick material may be made from a cellulose, plastic or ceramic material. The wick material width is between 0.1 mm and 22 mm, more preferably between 1 mm and 10 mm, most preferably between 5 mm and 10 mm. In the preferred embodiment the material is a pure cellulose material of width 8 to 10mm. A wider wick can transport more liquid than a correspondingly narrower wick. The maximum width of the wick is such that it must be able to fit within the constraints of existing mat devices.

A further feature that assists in achieving the desired target range and control of the emanation rate is the seal 20 across the wick 6, which affects the emanation rate and the potential for a vacuum to form in the reservoir 4. The seal 20 is affected by the thickness of the wick and thus the wick thickness can determine the emanation rate. A tight seal 20 will cause a partial vacuum or pressure differential between the reservoir 8 and the atmosphere. The pressure in the reservoir 4 is reduced as liquid is removed from the reservoir 4 by the wicking action thus forming a partial vacuum. Too much vacuum will reduce the wicking rate and potentially may completely stop the wicking. Too little vacuum and the solution may leak out of the aperture 14 under gravity. The thickness of wick 6 used has been proven to affect seal 20 across wick 6. If the wick material is too thick it is unable to be adequately sealed between the upper and lower layers 8 and 10 of the refill (in a preferred embodiment 250micron aPET and 30 micron MYLAR^® film). A poor seal around the wick causes the liquid in the reservoir to flow out of the refill under the effect of gravity or simply by applying a pressure to the reservoir. This is unacceptable to the consumer as they will come in contact with the solution. It is thus desirable to have a wick thickness that gives a seal that can withstand slight pressure however is not sealed so much that the flow is restricted lower than the desired emanation rate for bite inhibition.

The wick material thickness chosen is between 20 — 600 micron, more preferably 100 - 300 micron, most preferably 180-220 micron. In the preferred embodiment the material is a pure cellulose material of thickness approximately 200 micron.

Another feature/aspect of the device 2 that assists in achieving the target range and controlling the emanation rate is the size of aperture 14. It has been shown that by altering the size of aperture 14 at the emanation point, the release rate from the refill/reservoir can be correspondingly altered. A larger emanation aperture corresponds to a higher release rate. The aperture is between 0.1 mm and 20 mm in diameter, more preferably between 1 mm and 10 mm, most preferably between 2 mm and 5 mm. The aperture 14 may have any particular shape including but not limited to circular, square, rectangular or an irregular shape. In the preferred embodiment the aperture is circular with a diameter of 5mm.

Experiments - Insulating layer

Experiments were conducted using various insulating layers. The surface temperature of the heater on several mat devices was measured using a thermocouple. The temperature of the mat devices was found to be in the range of 100-18O⁰C however more generally between 120-160⁰C. At temperatures above 120⁰C MYLAR^® film is not thermally stable and becomes brittle. It is thus important to reduce the temperature to below this point. In a further experiment several types of insulating materials were placed upon an exposed heating element of a "SBP" mat device from Brazil and the temperature recorded. Some examples of temperatures measured included; Blank device with no insulation, 135-15O⁰C lmm thick cellulose material, 100-105⁰C 1.2mm thick 1 ply grey cardboard, 105⁰C

1.0mm thick M Flute corrugated cardboard, 105-115⁰C δ

2.8mm thick cellulose mat material, 80-90⁰C.

It is known that the vapour pressure of a solvent is a function of temperature thus by controlling the temperature at the emanation aperture, the emanation rate can be controlled. It can thus be seen that the insulating material does affect the temperature at the emanation aperture and thus can control the release rate of the refill.

Experiments - Wick width

In relation to the wick width, an experiment was conducted in which four refill devices were made. Two refills had a 5mm wide wick whilst the other two refills had a 10mm wide wick. The solution consisted of 6% transfluthrin, 1% BHT and 93% isopropyl myristate. The material of the first and second layers was made from 300micron aPET. The refill did not have a backing board and was placed directly on the heater plate. The wick was made from 600 micron thick cellulose paper. The seal across the wick and surrounding seals were made by a "vertrod" impulse heat sealer. After 64 hours of continuous operation the refills with a 5mm wide wick had an average emanation rate of 5.9mg/hr, whilst the refills with the 10mm wide wicks gave an emanation rate of lO.lmg/hr. It can thus be seen that the width of the wick can be used to control the emanation rate of the refill.

Experiments - Wick Thickness

An experiment was conducted using several refills whereby several wicks of different thickness were tested to see the effect on the emanation rate. The wicks tested included;

Tissue Paper - 70micron thick - 50gsm Photocopy paper - 1 OOmicron thick - 80gsm

Whatman 4 filter paper - 205micron thick - 96gsm Dyecor wick - 600micron thick -300gsm

All devices were made with a 3mm aperture, and used a solution consisting of Isopar M and Transfluthrin with the exception of the Whatman 4 set which used a solution consisting of 50% Isopar M and 50% Isopar V.

Release rate profiles of the tissue paper, photocopy paper and Whatman 4 filter paper are presented in Figure 4. From the profile it can be seen that the tissue paper gave a release rate of <2mg/hr. The photocopy paper gave a release rate up to 5mg/hr however this was significantly reduced over time. This was caused by a vacuum building in the reservoir as described previously. The Whatman 4 filter paper gave a relatively consistent release rate around 3mg/hr. The Dyecor wick was unable to be adequately sealed due to the wick thickness and liquid flowed out of the refill when pressure was applied. In this way the thickness of the wick material can affect the seal and can be used as a method control the release rate of the refill.

Experiments — Aperture Size

Another experiment was conducted in which four refill devices were made. The first layer 8 was made from 250-micron thick aPET. The reservoir 4 was thermoformed into a trapezoidal shape with a volume of l-2ml. An emanation aperture was cut into the upper layer using a circular hole punch. The second layer 10 was made from 30-micron thick MYLAR^®. The wick 6 was made from 200 micron thick, Whatman 4 filter paper. The wick dimensions were 10mm wide x 30mm long. The wick was heat sealed between the layers 8 and 10 using an impulse bag sealer with a 10mm wide seal. The upper aPET layer 8 was heat sealed to the MYLAR^® layer using a bag sealer. The insulating layer 18 consisted of a mosquito mat made from 100% cellulose.

The mat dimensions were 35mm long x 22mm wide x 2.8mm thick. The upper materials were not glued to the insulating layer for this experiment. The solution 12 used was combination of Isopar V and M in a ratio of 50 to 50. No active was used in this experiment. The refills were filled with ~0.7g of solution using a calibrated pipette. The electrical devices used were a standard mosquito mat device from Brazil called a SBP device. Two of the refills where made with a 5mm emanation hole and two refills were made with a 3mm diameter hole.

Results for this experiment are presented in Figure 3A and 3B. In the release profile shown in Figure 3 A, refill device numbers 37 and 40 had a 5mm aperture, whilst refill device numbers 38 and 39 had a 3mm diameter aperture. It can clearly be seen that refill 37 and refill 40 had an emanation rate of 4-6mg/hr which is significantly greater than the 3mm aperture refills which were 2-4mg/hr. In this way the size of the emanation aperture can be used as a method control the release rate of the refill.

Active Ingredients

It will be appreciated that one or more vapour active pyrethroids may be employed in the present invention. It will be understood that vapour active pyrethroids are those that are volatile at ambient temperature without heat or combustion. The volatile pyrethroids are preferably selected from the group consisting of metofiuthrin transfruthrin, empenthrin, methothrin, tefluthrin, d-allethrin, prallethrin, esbiothrin and fenfiuthrin. Preferably, the vapour active pyrethroid is metofiuthrin or transfluthrin. Metofluthrin has high potency against mosquitoes. The chemical name of metofluthrin is 2₅3₅5,6-tetrafluro-4-(methoxymethyl)benzyl(EZ)-(lRS,3RS;lRS,3SR)-2,2-dimethyl- S-førop-l-enyOcyclopropanecarboxylate. Metofluthrin is available from Sumitomo Chemical Company. The chemical name of transfluthrin is [(2,3,5,6-tetrafTuoro- phenyl)methyl] IR, 3R-(2,2-dichlorethenyl)-2,2-dimethylcyclopropane-carboxylate.

Example - Effectiveness of refill of present invention

A "vapour emanation device" according to the present invention containing 10% transfluthrin as the active ingredient was compared with a Rodasol Liquid Emanating Device (LED) containing Esbiothrin 1.8%. The trial was carried out at Agrisearch laboratories Gosford, NSW as per their LEDs protocol which is summarised below.

The methodology employed is as follows:

The study was conducted in a ventilated test chamber (20 cubic metres) at a temperature of between 28.1°C and 29.2 °C. The relative humidity was ambient and ranged from 36% to 57%.

Mixed sex adult 7 to 10 day old Dengue mosquitoes (Aedes aegypti) were used in this study. There were 50 female mosquitoes released per replicate and a variable number of male mosquitoes. The mosquitoes were collected and immobilised. Male and female mosquitoes were added to a container until 50 female mosquitoes were obtained. Because only female mosquitoes bite human subjects, the number of males present in each trial was irrelevant. The mosquitoes were allowed to recover for at least one hour before being used for testing.

A positive air flow of 0.4 metres/second was generated into the chamber and air was passively vented from the chamber. Positive controls were used in the form of commercially available Rodasol LEDs aged to 10 days as well as "no treatment' controls. Each refill was placed into an SBP mat device and allowed to run cyclically,

10 hours on/14 hours off to imitate normal consumer use. Periodically the device was introduced into the large testing chamber for bioefficacy testing as per the normal

Agrisearch LED protocol. Treatments were placed on the floor in the test chamber, and were allowed to run for 5 minutes before all mosquitoes were brought into the chamber and released.

The devices continued to operate during the assessments and were stopped at the completion of the test period.

Starting from 10 minutes after the mosquitoes were released, an assessment was made by one human subject of the mosquito landings and bites over a 5 minute period.

Whilst seated in the chamber, the subject recorded the total number of females that initiated a bite on the subject's legs, as well as the number of females that landed without initiating biting. ^' Mosquitoes were permitted to probe the subject but not permitted to bite the subject, and were chased away prior to this occurring. The same human subject was used for all assessments. Tables 1 and 2 show percentage landing inhibition and percentage bite inhibition for each device used in the trial after 15 minutes exposure of the Aedes aegypti mosquitoes to each treatment. The results shown in the Table 2 are the means of 3 replicates.

Each refill was allowed to run cyclically, 10 hours on and 14 hours off to imitate normal consumer use. Table 2 also presents the different times at which the devices were tested. Some tests were conducted at the end of a cycle whilst other tests were conducted as the device was just starting. It is important that the device begins to work rapidly once switched on and also at the end of its normal operating cycle.

Percentage landing inhibition refers to the number of mosquitoes which landed on the subject in the absence of any treatment (untreated control), minus the number of mosquitoes which landed on the subject in the presence of a treatment, divided by the number of mosquitoes which landed on the subject in the absence of any treatment, expressed as a percentage. Landing inhibition was assessed between 10 to 15 minutes of the exposure of the Aedes aegypti mosquitoes to each vapour emanating device treatment.

Percentage bite inhibition refers to the number of mosquitoes which probed or attempted to bite the subject in the absence of any treatment (untreated control), minus the number of mosquitoes which attempted to bite the subject in the presence of a treatment, divided by the number of mosquitoes which attempted to bite the subject in the absence of any treatment, expressed as a percentage. It will be appreciated that, as mosquitoes must first land before attempting to bite, of necessity, percentage bite inhibition will always be higher than or equal to percentage landing inhibition. Bite inhibition was assessed from 10 to 15 minutes of the exposure of the Aedes aegypti mosquitoes to each treatment. From tables 1 and 2 it can be seen that the vapour emanating device according to the current invention gave results for landing inhibition and bite inhibition that were statistically the same as that of a liquid emanating device currently on the market.

Table 1: Percentage Landing Inhibition of Aedes aegypti mosquitoes after 15 minutes exposure to current invention and compared to liquid emanating device currently on the market.

Table 2: Percentage Bite Inhibition of Aedes aegypti mosquitoes after 15 minutes exposure to current invention and compared to liquid emanating device currently on the market.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A vapour emanation device comprising: a reservoir storing a solution; a wick adjacent an aperture open to the atmosphere, the wick being in communication with the solution in the reservoir through a wick seal; a first layer and a second layer of material between which the wick is located and sealed; and an insulating layer in contact with the second layer and heated by a heater; the aperture formed in the first layer; such that heat radiated by the heater is partially dissipated by the insulating layer to reduce the temperature of the second layer and the wick in the vicinity of the aperture to enable control of the rate of emanation of the solution through the aperture within a predetermined target emanation rate range.

2. A vapour emanation device according to claim 1 : wherein a cross-sectional area of the wick is dimensioned to assist with the control of the rate of emanation of the solution through the aperture.

3. A vapour emanation device according to claim 1 or claim 2 wherein the aperture is dimensioned to assist with the control of the rate of emanation of the solution through the aperture.

4. A vapour emanation device according to any one of the previous claims wherein the first layer has a thickness between 20 microns and 1000 microns.

5. A vapour emanation device according to claim 4 wherein the first layer has a thickness between 100 microns and 500 microns.

6. A vapour emanation device according to claim 5 wherein the first layer has a thickness in the order of 250 microns.

7. A vapour emanation device according to any one of the previous claims wherein the first layer of material comprises any one of plastics, metal foil or laminates of plastic or metal foil.

8. A vapour emanation device according to claim 7 wherein the first layer of material is aPET.

9. A vapour emanation device according to any one of the previous claims wherein the second layer has a thickness between 10 microns and 1000 microns.

10. A vapour emanation device according to claim 9 wherein the second layer has a thickness between 25 microns and 100 microns.

11. A vapour emanation device according to claim 10 wherein the second layer has a thickness in the order of 30 microns.

12. A vapour emanation device according to any one of the previous claims wherein the second layer of material comprises any one or more of plastics, metal foils, cellulose or ceramic.

13. A vapour emanation device according to any one of claims 1 to 12 wherein the second layer of material comprises a laminate of polyester and aPET heat sealed to the first layer.

14. A vapour emanation device according to any one of claims 2 to 13 wherein the cross-sectional area of the wick is altered by varying the thickness of the wick.

15. A vapour emanation device according to claim 14 wherein the wick thickness is between 20 microns and 600 microns.

16. A vapour emanation device according to claim 15 wherein the wick thickness is between 100 microns and 300 microns.

17. A vapour emanation device according to claim 16 wherein the wick thickness is between 180 microns and 220 microns.

18. A vapour emanation device according to any one of claims 2 to 17 wherein the cross-sectional area of the wick is altered by varying the width of the wick.

19. A vapour emanation device according to claim 18 wherein the wick width is between 0.1 mm and 22 mm.

20. A vapour emanation device according to claim 19 wherein the wick width is between 1 mm and 10 mm.

21. A vapour emanation device according to claim 20 wherein the wick width is between 5 mm and 10 mm.

22. A vapour emanation device according to claim 21 wherein the wick width is between 8 mm and 10 mm.

23. A vapour emanation device according to any one of the previous claims wherein the wick comprises any one of cellulose, plastics or ceramic material.

24. A vapour emanation device according to any one of claims 3 to 23 wherein the diameter of the aperture is between 0.1 mm and 20 mm.

25. A vapour emanation device according to claim 24 wherein the diameter of the aperture is between 1 mm and 10 mm.

26. A vapour emanation device according to claim 25 wherein the diameter of the aperture is between 2 mm and 5 mm.

27. A vapour emanation device according to any one of the previous claims wherein the target emanation rate range is from 0.1 mg/hr to 50 mg/hr.

28. A vapour emanation device according to claim 27 wherein the target emanation rate range is from 1 mg/hr to 20 mg/hr.

29. A vapour emanation device according to claim 28 wherein the target emanation rate range is from 3 mg/hr to 15 mg/hr.

30. A vapour emanation device according to any one of the previous claims wherein the thickness of the insulating layer is between 0.1 mm and 4 mm.

31. A vapour emanation device according to claim 30 wherein the thickness of the insulating layer is between 1 mm and 3 mm.

32. A vapour emanation device according to claim 31 wherein the thickness of the insulating layer is between 2 mm and 2.8 mm.

33. A vapour emanation device according to any one of the previous claims wherein the insulating layer comprises any one of cellulose, plastics or ceramic material.