AU2003201533A1

AU2003201533A1 - Fumigant formulation

Info

Publication number: AU2003201533A1
Application number: AU2003201533A
Authority: AU
Inventors: Simon Robert Bishop; Robert Francis Ryan
Original assignee: BOC Gases Australia Ltd
Current assignee: BOC Ltd Australia
Priority date: 2002-01-25
Filing date: 2003-01-28
Publication date: 2003-09-18
Anticipated expiration: 2023-01-28

Description

TITLE: FUMIGANT FORMULATION TECHNICAL FIELD

The present invention relates to a non-flammable fumigant formulation comprising ethyl formate as the active ingredient. BACKGROUND ART

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

With an increasing consumer demand for 'organic' food stuffs, pressure is being placed on various chemicals etc used for insect control of commodities. Approval to use the term 'organic' for a chemical is biased towards natural products and to products that do not contaminate the treated commodities with pesticide residues.

Ethyl formate [EtF: C₃H₆O₂] is used as a flavour essence and is a low risk GRAS (Generally Regarded As Safe) food additive. It is used as a flavour in lemonade and essences for the manufacture of rum and arrac.

Ethyl formate is made by reacting ethanol with formic acid. Ethyl formate is hydrolysed/metabolised back to these naturally occurring chemicals when used to fumigate commodities and accordingly, would not persist in the environment. "Formic acid and ethanol are widely distributed in the plant and animal kingdom. These two hydrolysis products of ethyl formate are present in the atmosphere in very large amounts, and ethyl formate is also present in some samples. It is therefore difficult to see the use of ethyl formate as a fumigant contributing to global atmosphere problems" (PostHarvest News and Information 1999 Vol.10, No 1, pp 7N-12). For this reason, ethyl formate is viewed as a real alternative to the well-known fumigant methyl bromide, now listed on the Montreal Protocol as an ozone depletory and is currently being phased out. Methyl bromide will not be available after 2005 in developed countries and 2015 in developing countries.

Ethyl formate has also been investigated by various parties as an insecticide. Ethyl formate has been used in the protection of tobacco, cereals and dried fruits and is currently used in large volumes in the treatment of dried grapes.

It is understood that ethyl formate works quickly and is therefore useful for rapid disinfestation in grain storage applications and fruit and vegetable treatment. The naturally occurring ethyl formate achieves a residue-free status since it decomposes on or is easily aerated from the treated product.

Ethyl formate is quite volatile having a boiling point of 54°C, a vapour pressure of 194 mm Hg and a low flash point. Moreover, ethyl formate is a highly flammable liquid in its natural state, posing a dangerous fire and explosion risk. Due to these flammability and associated handling issues the potential for ethyl formate as a commonly used fumigant has not yet been realised.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. It is an object of the present invention in its preferred form to provide a nonflammable fumigant formulation without reducing the efficacy of the active agent in the fumigant. DISCLOSURE OF THE INVENTION

In a first aspect, the present invention provides a fumigant comprising ethyl formate combined with a diluent in a quantity sufficient to render the fumigant nonflammable while at least retaining the efficacy of the ethyl formate.

In one embodiment, the diluent is present in a quantity sufficient to render the fumigant non-flammable while retaining the efficacy of the ethyl formate. In another embodiment, the diluent is present in a quantity sufficient to render the fumigant non- flammable while synergistically enhancing the efficacy of the ethyl formate.

The Applicants of the present invention have discovered that the flammability and handling concerns associated with ethyl formate can be overcome by formulating the active in a diluent. It would normally be expected that a diluent would decrease the efficacy of an active ingredient, such as ethyl formate, in a fumigant. However, it has surprisingly been found that certain diluents can not only render the active nonflammable but also at least retain and in some cases enhance the efficacy of the active. A particularly preferred diluent is carbon dioxide. Hydrofluorcarbons could also fill this role however they are much more expensive than liquid CO . The CO can act as a diluent, solvent and propellant. Clearly having one material perform each of these functions has significant advantages.

By using such a combination of 'organic' active agents and a diluent, a nonflammable fumigant can be provided for safe use on so called 'organic' produce. The fumigant can be distributed as an aerosol or vapour/fog over the material to be treated. The fumigant allows for disinfestations of food and other commodities and provides for suitable insecticide/pesticide treatment of 'organic' produce without affecting its 'organic' status.

The term "efficacy" as used throughout the specification refers to efficacy of the fumigant as would be understood by persons skilled in the relevant art and includes biocidal, insecticidal and fungicidal efficacy.

It is envisaged that the invention may be used in a wide variety of environments including quarantine disinfestations of imported produce, horticulture, treatment of domestic food commodities, grain storage etc. In one embodiment, the ethyl formate and the diluent are provided separately.

That is, each of the components of the fumigant formulation of the present invention may be provided to the area being fumigated separately. For example, in order to reduce the possibilities of ignition, the area may first be filled with the gaseous diluent with the ethyl formate being added later. In an alternative embodiment, the ethyl formate and the diluent are provided in a premixed form. In this embodiment it is envisaged that the fumigant is prepared and packaged off site and later transported to the area requiring fumigation.

Preferably, the proportion of ethyl formate vapour in carbon dioxide gas is up to about 25.0 % v/v, more preferably up to about 15.0 % v/v, more preferably up to about 12.5 % v/v. Most preferably, the proportion is about 10.8 % v/v.

The present Applicants have discovered that by combining ethyl formate with a diluent they are able to provide the user, for example growers or farmers, with a simple and safe fumigation product.

In a second aspect, the present invention provide a packaged fumigant product comprising a pressurised vessel containing a fumigant formulation of ethyl formate combined with a diluent in a quantity sufficient to render the fumigant non-flammable upon release from the pressurised vessel while at least retaining the efficacy of the ethyl formate.

As mentioned above, in a preferred embodiment, the diluent is carbon dioxide. Preferably, the formulation comprises up to about 22 wt %, more preferably between about 10.0 wt % to about 20.0 wt % of ethyl formate in liquid carbon dioxide. Most preferably, the formulation comprises about 16.7 wt % of ethyl formate in liquid carbon dioxide. The vessels used to package the fumigant formulation of the present invention may be any suitable shape and size. For example, the vessel could be a relatively small gas cylinder suitable for domestic use or alternatively, a larger pressurised vessel for industrial applications. In a third aspect, the present invention provides a method of producing a fumigant comprising the step of combining ethyl formate and a diluent wherein the amount of ethyl formate and diluent are selected to render the fumigant non-flammable while at least retaining the efficacy of the ethyl formate.

In a fourth aspect, the present invention provides a method of fumigating a volume in need thereof comprising filling the volume with a non-flammable fumigant comprising ethyl formate combined with a diluent in a quantity sufficient to render the fumigant non-flammable while at least retaining the efficacy of the ethyl formate. The volume may be an enclosed space containing for example a stored commodity, or alternatively a domestic area. In an fifth aspect, the present invention provides a method of rendering an ethyl formate fumigant non-flammable comprising the step of combining the ethyl formate with a diluent in a quantity sufficient to render the fumigant non-flammable while at least retaining the efficacy of the ethyl formate.

In a sixth aspect, the present invention provides a method of enhancing the efficacy of ethyl formate comprising combining the ethyl formate with a synergistically effective amount of diluent.

Preferably, the diluent is added in a quantity sufficient to render the resultant fumigant non-flammable.

It will be understood by persons skilled in the relevant art that the amount of fumigant that is provided to the volume being fumigated varies depending on the level of infestation and the types of species present. The amount of fumigant required is then calculated using a combination of fumigant concentration and exposure time. In general a lower concentration requires an increased duration and a higher concentration is suitable for shorter durations. Concentrations of ethyl formate may range from a few g/m³ up to over 90 g/m³.

Tests have been conducted using ethyl formate at about 12.5 g/m³ as well as at 30 to 40 g/m³ and above 70 g/m³. These have all been shown to be effective amounts to kill the target organisms. Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". BRIEF DESCRIPTION OF THE FIGURES

The present invention will now be described by way of example only with reference to the accompanying drawings.

Figure 1. Schematic representation of the test developed for assessing the flammability of ethyl formate. Figure 2. Graph showing the theoretical vapour concentrations of ethyl formate vs measured vapour concentrations of ethyl formate for the flammability test shown in Figure 1. Figure 3. Calibration plot for the flammability test of Figure 1.

Figure 4. A plot of the limits of flammability for ethyl formate in carbon dioxide/air mixtures.

Figure 5. The efficacy of a fumigant comprising ethyl formate alone with respect to three insect species. Figure 6. Bar graph showing the effect of varying amounts of carbon dioxide on the toxicity of ethyl formate. Figure 7. Bar graph showing the effect of the fumigant according to a first embodiment on a single insect species at different stages in its life cycle. Figure 8 A. Diagrammatic representation of the set up of Room #1 (tested with ethyl formate alone) Figure 8B. Diagrammatic representation of the set up of Room #5 (tested with combination of ethyl formate and carbon dioxide)

Figure 9. Table showing the varying concentrations of ethyl formate at the sample sites in Room # 1. Figure 10. Table showing the varying concentrations of ethyl formate at the sample sites in Room # 5. Figure 11. Table showing the insects counts in Rooms #1 and #5 in the week after fumigation. Figure 12. Table showing the mortality rates per week after fumigation for Room #1. Figure 13. Table showing the mortality rates per week after fumigation for Room #5. MODE(S) FOR CARRYING OUT THE INVENTION

The present invention will be described, by way of example only with respect to the following embodiments. Flammability of Ethyl Formate/Diluent Fumigant As may be known to those skilled in the art, fuel vapours and gases are only flammable or explosable at concentrations between their Lower (LEL) and Upper (UEL) Explosability Limits. These limits are normally determined by mixing known proportions of a fuel with fresh air, containing approximately 21% v/v oxygen. The mixtures are then tested for propagation of flame after exposure to a suitable ignition source.

The Applicants have determined that it is possible to prepare mixtures of the normally flammable active agent, ethyl formate, in a suitable diluent gas such that when this mixture is exposed to air, it remains below its LEL for all proportions. Of course, commercial and operational considerations would favour mixtures containing the maximum amount of active agent, while still maintaining safe operation below the LEL. • Ethyl formate flammability test set up A test set up was developed as shown in Figure 1. The set up allows continuous metering and mixing of known proportions of ethyl formate vapour, carbon dioxide and air. The set up comprises sources of compressed air 1 and carbon dioxide 2. A

Wosthoff positive displacement gas mixing pump 3 provides a convenient method of proportioning the carbon dioxide with air and pumping the resulting mixture through the test set up.

A liquid syringe pump 4 is provided downstream of the pump 3. Liquid ethyl formate is dispensed via this syringe at a constant flow rate.

A heat exchanger 5 is provided downstream of the liquid syringe pump. The heat exchanger is a coiled length of aluminium tubing 6 placed in a water bath at a temperature approximately 10°C above the boiling point of the ethyl formate. This produces ethyl formate vapour. The unmixed ethyl formate vapour and CO /air mixture then passes to a static mixer 7.

The resultant mixed fumigant leaves the static mixture 7 and is diverted via valve 8 to a paramagnetic oxygen analyser 9 and an ignition tube 10. In the ignition tube 10, a spark is provided by an ignition source 11 and the fumigant gas passed across this spark to determine the flammability/flame propagation.

In this test the ethyl formate used was a supply of ERANOL™ is the ORICA Chemnet veteran insecticide currently registered by the Australian National Registration Authority - Approval No: 48346/1 and containing 98 w/w % ethyl formate.

• Test for Coudensation of vapour within the test set up

Since the ethyl formate is heated above its boiling point, mixed with the carbon dioxide/air mixture and then allowed to cool, it was necessary to establish that the vapour does not condense inside the test instrumentation and thereby contribute to unreliable results.

A simple test was conducted whereby calculated concentrations of ethyl formate were compared to the achieved concentrations. 'In house' knowledge was used to calculate the theoretical vapour concentrations using the known properties of ethyl formate and the airflow delivery rate of the Wosthoff pump. The well established technique of Oxygen Depletion was then used to determine vapour concentrations and a plot of the data obtained from this experiment is given in Figure 2. Examination of this plot shows a general one to one (1:1) correlation. It was observed, however, that a second order quadratic curve fitted the data better than the linear plot and accordingly, the data was replotted as shown in Figure 3, to produce a calibration graph or syringe flow rate versus ethyl formate vapour concentration as an aid for setting vapour concentrations.

• Test procedure

Flammability tests were then conducted by introduction of a known flow of ethyl formate vapour into the known flow of the Wosthoff pump 3. At least 7 minutes were allowed to elapse for each adjustment of the syringe pump flow and any ignition tests to ensure constant concentrations.

For tests involving the addition of carbon dioxide, the proportions of air and CO were set on the pumps controls. At least 10 minutes were allowed to elapse between adjustment of the CO₂/air proportions and ignition tests. Ignition tests involved switching a high voltage across an approximately 3 to 5mm gap within the test gas mixture. A test mixture was judged to be ignitable if a clear propagation of the flame away from the ignition source was observed. • System suitability

The known LEL and UEL of ethyl formate is 2.8 and 16% v/v respectively. After establishing that the test set up could be used reliably for concentrations up to 20% ethyl formate v/v, tests where conducted to find the flammability limits. The lower flammability limit determined by the test is between 3.1 and 3.6% v/v.

The literature value is around 3.0 % v/v. The upper flammability limit as determined experimentally was between 15.0 and 15.7% v/v. The literature value being 16% v/v. While the test set up over estimated the LEL and under estimated the UEL, it is believed this is due to the small size of the flow ignition tube or amount of ignition energy. In any case, the differences are not great.

• Results of chemical tests

A series of tests were conducted to provide a plot of ethyl formate flammability in CO₂/air mixtures. This is provided under Figure 4. The plot shows the characteristic 'nose' shaped zone of flammability and includes the practically determined LEL and UEL. "+" indicates an ignition at the limits of flammability for a particular mixture of gasses. "-"indicates a test showing an inert mixture at the limits of ignition.

By reviewing Figure 4, it is possible to determine what proportion of ethyl formate in a diluent gas such as carbon dioxide will remain inert in all proportions with air. The line A/B shown on Figure 4 has the maximum slope that can be achieved while still remaining wholly below the experimentally determined Lower Explosive Limits and passing through the origin. This slope indicates the maximum proportion of ethyl formate vapour in a carbon dioxide gas which is inert in all proportions with air. The slope equals 6/40 or 15% v/v.

Accordingly, taking into consideration experimental error or fluctuations, differences between literature and experimental values for LEL and UEL of ethyl formate, a conservative and safe maximum of ethyl formate vapour and carbon dioxide gas would be 12.5% v/v ethyl formate in carbon dioxide. A preferred formulation is 15.5 wt % ethyl formate in liquid CO₂. In use, this vaporises to form 10.8 vol % ethyl formate in gaseous CO₂. It is also believed by the Applicants that these figures may alter when applied on a larger scale with a larger ignition source. Efficacy of Ethyl Formate/Diluent Fumigant

As discussed above, the Applicants of the present invention have discovered that a non-flammable fumigant may be produced by combining the usually flammable active chemical ethyl formate with a diluent such as carbon dioxide. Importantly, the efficacy and effectiveness of the ethyl formate in the non-flammable fumigant is at least retained. In fact, research shows that carbon dioxide may enhance the toxicity of ethyl formate to insects, particularly adult insects. Moreover, carbon dioxide has been shown to improve the distribution and penetration of the ethyl formate. Example 1; Efficacy of ethyl formate in three insect species of stored product pest. The effect of ethyl formate toxicity in three species of stored product pest: the flour beetle (Tribolium castaneum, Tc), rice weevil (Sitophilus oryzae, So) and the lesser grain borer (Rhyzopertha dominica, Rd) was investigated. The relevant mortality rates are shown in Figure 5. Figure 5 shows the percentage mortality of the three adult insects against ethyl formate vapour concentration after 24 h exposure (200 insects per level, 60% relative humidity, no grain).

The most tolerant adult insect was T castaneum; its mortality over a range of concentrations was substantially different to R. dominica. A concentration of ethyl formate which resulted in low mortality over 24 h in the tolerant species was 12.5 g m^"3. Example 2: The effect of CO? on ethyl formate toxicity in three species of stored product pest.

The effect of carbon dioxide on ethyl formate toxicity was investigated in three species of stored product pest: the flour beetle (Tribolium castaneum), rice weevil (Sitophilus oryzae) and the lesser grain borer (Rhyzopertha dominica). The mortality in T. castaneum due to ethyl formate increased from 3 to 99% in the presence of fumigant and 5% carbon dioxide, as shown in Table 1.

A concentration of 12.5 g m^"3 ethyl formate was used in this experiment since this particular concentration resulted in low mortality over 24 h in the tolerant species, T. castaneum, as shown in Example 1. Table 1. Percentage mortality of adult stored product insects exposed to ethyl formate (12.5 g m^"3) alone or combined with carbon dioxide (5% v/v) over 24 h. Relative humidity 60%, no grain, 200 adults per level.

T. castaneum.

The toxicity of the fumigant mixture was also investigated in immature stages of T. castaneum. The addition of 5% carbon dioxide to ethyl formate enhanced the toxicity in immature insects but not as significantly as the enhancement of toxicity in adult insects as shown below in Table 2.

Table 2. Percentage mortality of immature T. castaneum exposed to ethyl formate alone or combined with 5% carbon dioxide (v/v) over 24 h. Conditions include relative humidity 60%, no grain, 200 adults per level.

Example 4; Effect of CO? on ethyl formate toxicity in adult T.castaneum over a range of

CO? concentrations.

The effect of carbon dioxide on ethyl formate toxicity in adult T. castaneum was determined over a range of carbon dioxide concentrations. Figure 6 shows the effect of carbon dioxide (0 - 20% v/v) on the toxicity of ethyl formate (12.5 g m^"3) to adult

Tribolium castaneum over 24 h. Conditions include 60% relative humidity, no grain, 200 adults per level. It can be seen from Figure 6 that the maximal effect of the mixture was reached at around 5% carbon dioxide (v/v) but over 90% mortality was achieved at CO₂ concentration as low as 2%. Example 5: The effect of CO? on ethyl formate toxicity on mixed stage cultures of

Sitophilus oryzae.

A further test was conducted in order to more fully investigate the potential for enhanced activity of a fumigant comprising a mixture of ethyl formate and carbon dioxide as opposed to ethyl formate alone. The activity of a fumigant comprising ethyl formate and 5% CO₂ was assessed against mixed stage cultures of the most tolerant insect species, usually Sitophilus oryzae. While adult T. castaneum were the most tolerant of the three species towards ethyl formate (as shown in Table 1), juvenile stages of the internally developing

S. oryzae have been shown in related research to be the most tolerant overall. Therefore, S. oryzae was used to determine the effect of carbon dioxide on ethyl formate toxicity in mixed age cultures.

A mixed age S. oryzae culture was fumigated with ethyl formate or a mixture of ethyl formate and 5% carbon dioxide, and the number of adults emerging from the grain over a 6 week period after treatment were removed and counted. The concentration of ethyl formate selected for the fumigation was 33 g m^"3. The number of adults emerging from the treated grain was compared with the number from untreated mixed age cultures or 5% carbon dioxide treated.

Figure 7 shows the mean number of Sitophilus oryzae adult insects emerging after treatment of mixed age cultures with 33 g m^"3 ethyl formate (EF) or EF plus 5% carbon dioxide for 24 h compared with control or 5% carbon dioxide treatment. The results are the mean emergence of duplicate samples.

As shown in Figure 7, the effect of a 24 h exposure to ethyl formate/CO₂ fumigation on adults, eggs and young larvae of S. oryzae in the culture was dramatic. These finding suggest that carbon dioxide serves as an effective synergist when combined with ethyl formate to improve adult, egg and young larvae kill.

Example 6: Fumigation trials using a fumigant according to the present invention and in comparison to liquid ethyl formate. Experiments were conducted in order to compare the distribution and efficacy of a fumigant comprising ethyl formate alone and a fumigant comprising ethyl formate in combination with carbon dioxide.

• Set up

Two seed store rooms were set up: Room #1 - fumigated using ERANOL™ (ethyl formate alone).

Room #5 - fumigated using EtF/CO formulation comprising 16.67 wt % ethyl formate in liquid CO₂.

The plans for seed store rooms #1 and #5 and the placement of sample lines and insect cages is shown in Figure 8. Sample sites 1, 2, 3 and 4 are in room samples; sample sites 5 and 6 are in "buckets" or wire bins filled with bags of samples; and sample site 7 is in the middle of a bag of sorghum.

• Procedure and events Seed Room #1

7 sampling lines into the room. 1 to 4 sampling room air

5 and 6 into the middle of crates of commodity

7th line placed in the middle of a 25kg bag of sorgham Fumigation of Room 1 started at 2.05pm on day 1 room volume = 260 cu meters ERANOL™ added to 8 trays placed on the floor = 11 L

11 litres of ERANOL™ is equivalent to 9.922 kg of ethyl formate. This equates to 0.902 kg EtF/L

Hobos into room at 2.52pm on day 1

Insects placed at the end of sample line 1-1,1-2,1-3 and 1-6 Day 4 8:40am Room #1 opened

30 mins later an environmental sample taken Seed Room #5 7 sampling lines into the room. 1 to 4 sampling room air

5 and 6 into the middle of crates of commodity

7th line placed in the middle of a 25kg bag of sorgham

Weight of EtF/C0₂ fumigant added Fumigation of room started at 11.20 am on day 1 First cylinder emptied by 11 :50 am 31

14:35pm on day 1 added an extra 7 kg of EtF/CO₂ fumigant (10 mins) 7 17:00pm on day 1 added another 4kg of EtF/CO₂ fumigant 4 9:00am on day 2 added 6kg of EtF/CO fumigant 6 10:55am on day 2 added 6kg to make cone up to 25mg/L 6

54 kg

Room opened at 9am on day 3 and a ventilation fan used to assist ventilation 2 Environmental samples taken.

• Photovac (Gas Chromatography) results

The concentration of ethyl formate at each sample site in each room was measured over the various time frames as shown in Figures 9 and 10. The average concentration measured in Room #1 was 9.19g/m and the average concentration measured in Room #5 was 19.92 g/m³. Accordingly, the concentration of ethyl formate at all sample sites was more than double using a fumigant according to the invention.

Most notably was sample site 7 where is took 42 hours to obtain a concentration of 12 g/m³ in Room #1 but took only about 4 hours to reach the same concentration in Room #5.

• Bioassay results

The insects tested in the seed rooms is shown below in Table 3.

Source species

1 QDPI QOS301 Oryzaephilus Sawtooth

2 QDPI RD569 Rhyzopertha Lesser grain borer

3 QDPI RD369 Rhyzopertha Lesser grain borer

4 QDPI TC931 Tribolium Flour beetle

5 QDPI CfO37 Cyrptolestes flat grain beetle

6 QDPI SO335 Sitophilus Grain weevil

7 QDPI LQLE Psocid Callosobruchus

8 SGRL Bruchids Callosbruchis Moree cow pea weevil

Table 3: Insects tested in seed rooms #1 and #5 The first insect count was done in the week after treatment, the results of which are shown in Figure 11.

The mortality rates by week were also calculated, the results of which are shown in Figures 12 and 13. It is evident from these results that the combination fumigant according to the invention is a more effective fumigant.

The fumigant, packaged fumigant product, methods of producing a fumigant and methods of fumigation may be embodied in other forms without departing from the spirit or scope of the present invention.

Claims

THE CLA S DEFINING THE INVENTION ARE AS FOLLOWS :- 1. A fumigant comprising ethyl formate combined with a diluent in a quantity sufficient to render said fumigant non-flammable while at least retaining the efficacy of said ethyl formate.
2. A fumigant according to claim 1, wherein said diluent is present in a quantity sufficient to render said fumigant non-flammable while retaining the efficacy of said ethyl formate.
3. A fumigant according to claim 1, wherein said diluent is present in a quantity sufficient to render said fumigant non-flammable while synergistically enhancing the efficacy of said ethyl formate.
4. A fumigant according to any one of the preceding claims, wherein said ethyl formate and said diluent are provided separately.
5. A fumigant according to any one of claims 1 to 3, wherein said ethyl formate and said diluent are provided in a premixed form.
6. A fumigant according to any one of the preceding claims, wherein said diluent is carbon dioxide.
7. A fumigant according to claim 6, wherein the proportion of ethyl formate vapour in carbon dioxide gas is up to about 25.0 % v/v.
8. A fumigant according to claim 7, wherein the proportion of ethyl formate vapour in carbon dioxide gas is up to about 15.0 % v/v.
9. A fumigant according to claim 8, wherein the proportion of ethyl formate vapour in carbon dioxide gas is up to about 12.5 % v/v.
10. A fumigant according to claim 9, wherein the proportion of ethyl formate vapour in carbon dioxide gas is about 10.8 % v/v.
11. A fumigant according to any one of the preceding claims, wherein said efficacy is insecticidal efficacy.
12. A packaged fumigant product comprising a pressurised vessel containing a fumigant formulation of ethyl formate combined with a diluent in a quantity sufficient to render said fumigant non-flammable upon release from the pressurised vessel while at least retaining the efficacy of said ethyl formate.
13. A packaged fumigant product according to claim 12, wherein said diluent is present in a quantity sufficient to render said fumigant non-flammable while retaining the efficacy of said ethyl formate.
14. A packaged fumigant product according to claim 12, wherein said diluent is present in a quantity sufficient to render said fumigant non-flammable while synergistically enhancing the efficacy of said ethyl formate.
15. A packaged fumigant according to any one of claims 12 to 14, wherein said diluent is carbon dioxide.
16. A packaged fumigant according to claim 15, wherein said formulation comprises up to about 22.0 wt % of ethyl formate in liquid carbon dioxide.
17. A packaged fumigant according to claim 16, wherein said formulation comprises from about 10.0 wt % to about 20.0 wt % of ethyl formate in liquid carbon dioxide.
18. A packaged fumigant according to claim 17, wherein said formulation comprises about 16.7 wt % of ethyl formate in liquid carbon dioxide.
19. A packaged fumigant according to any one of claims 12 to 18, wherein said efficacy is insecticidal efficacy.
20. A method of producing a fumigant comprising the step of combining ethyl formate and a diluent wherein the amount of ethyl formate and diluent are selected to render said fumigant non-flammable while at least retaimng the efficacy of said ethyl formate.
21. A method according to claim 20, wherein the amount of ethyl formate and diluent are selected to render said fumigant non-flammable while retaining the efficacy of said ethyl formate.
22. A method according to claim 20, wherein the amount of ethyl formate and diluent are selected to render said fumigant non-flammable while synergistically enhancing the efficacy of said ethyl formate.
23. A method of fumigating a volume in need thereof comprising filling said volume with a non-flammable fumigant comprising ethyl formate combined with a diluent in a quantity sufficient to render said fumigant non-flammable while at least retaining the efficacy of said ethyl formate.
24. A method according to claim 23, wherein said volume is an enclosed space.
25. A method according to claim 24, wherein said space contains a stored commodity.
26. A method according to claim 24, wherein said space is a domestic area.
27. A method according to any one of claims 20 to 26, wherein said ethyl formate and said diluent are provided separately to the volume.
28. A method according to any one of claims 20 to 26, wherein said ethyl formate and said diluent are provided to the volume in a premixed form.
29. A method of rendering an ethyl formate fumigant non-flammable comprising combining said ethyl formate with a diluent in a quantity sufficient to render said fumigant non-flammable while at least retaining the efficacy of said ethyl formate.
30. A method according to claim 29, wherein the quantity of diluent is sufficient to render said fumigant non-flammable while retaining the efficacy of said ethyl formate.
31. A method according to claim 29, wherein the quantity of said diluent is sufficient to render said fumigant non-flammable while synergistically enhancing the efficacy of said ethyl formate.
32. A method of enhancing the efficacy of ethyl formate comprising combining said ethyl formate with a synergistically effective amount of diluent.
33. A method according to claim 32, wherein said diluent is added in a quantity sufficient to render the resultant fumigant non-flammable.
34. A method according to any one of claims 20 to 33, wherein said efficacy is insecticidal efficacy.
35. A method according to any one of claims 20 to 33, wherein said diluent is carbon dioxide.