AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicants: John Peter Knight and Anthony Balding Invention Title: A DEVICE AND METHOD The following statement is a full description of this invention, including the best method for performing it known to me/us: A DEVICE AND METHOD FIELD OF THE PRESENT INVENTION The present invention relates to a device for fumigating a storage facility such as a grain silo. The present invention also relates to a method of installing a device for fumigating the storage facility. The present application is a divisional application of application 2008203480. BACKGROUND OF THE PRESENT INVENTION At present there are essentially two different forms of silos; sealed silos and unsealed silos. Unsealed silos have been in wide spread use for many decades. However, the current trend is in favour of sealed silos which offer a number of advantages including the ability to fumigate and provide greater control over the conditions under which grain is stored. Fumigation of silos using phosphide tablets is common practice for Australian growers. Phosphide tablets are often sold in the form of aluminium phosphide, calcium phosphide, or zinc phosphide and all forms yield phosphine when in contact with atmospheric water or ingested. Phosphine is an effective insecticide against rodents, mould, insects and immature insect forms including eggs, larvae and pupae of insects. On a practical level phosphide tablets are placed on trays or pans suspended in the top space above grain in the silo. Loading phosphide tablets onto the trays can be a dangerous task from the view point of climbing the silos and opening a hatch at the top of the silo. Occupational, Health and Safety (OHS) regulations require safety harnesses to be worn during this task to minimise injury. The fumigation tablets are usually left in the silo for up to 4 weeks and at the end of this period tablet residue in the form of powder is emptied from the pans. Again the danger in carrying out this task is working from the top of the silo and another, sometimes unpredictable risk, is the potential for wind to blow the tablet residue into the face of the operator or being spilt on the grain in the silo. 27006551 (GHMattm) P72404AU.2 14,07/ti Control over the aeration of silos is an important parameter affecting the quality of the grain stored in a silo. Generally speaking aerating silo allows greater control over moisture content and temperature of grain inside the silo. In the case of sealed silos, aeration has been achieved by blowing air into the silo or sucking air out of the silo by a motor or engine driven fan. The fan effectively creates air circulation or turbulence within the silo and due to the silo being sealed or otherwise air tight only nominal discharge or supply of air into the silo occurs. It is an object of the present invention to provide an alternative means for fumigating or aerating a storage facility such as a silo. SUMMARY OF THE INVENTION The present invention relates to a device that can be fitted to a silo and can be used to release a fumigating agent into the silo for fumigating granular material contained therein, the device includes: a chamber that can be fitted to extend through a wall of the silo and into which the fumigating agent can be loaded; a closure that can be opened and closed to allow access to the chamber for loading a fumigating agent into the chamber, and when fitted to the silo, the closure can be opened and closed from outside the silo; and an outlet in communication with the chamber, the outlet has openings that are sized so as to allow gas vapours of the fumigating agent to pass from the chamber into the silo. Throughout this specification to term "fumigating agent" or variations thereof include any material capable of disinfecting and include pesticides, insecticides or herbicide. The fumigating agent may be in any state including a gas, or a solid or liquid from which a gas evolves. In one example, the fumigating agent may be a tablet containing phosphide which releases a gas that can permeate a storage facility. Loading the fumigating agent in this example includes manually placing tablets containing phosphine, for example, tablets on a tray, into the chamber. In another example, the fumigating agent may be supplied in gaseous state, and the gas may be conveyed via 27 65_ I (GHManr) PF72404 AU 2 14M7/1 I -4 suitable piping into the chamber such as a fluoride containing fumigating agent and a sulfuryl fluoride containing fumigating agent. When the device is fitted to the silo, the device may extend through a side wall or bottom wall of the silo, and may include a flange extending outwardly of the device for butting against an external surface or internal surface of the walls of the silo. The openings of the outlet may be sized so as to prevent the passage of granular material from within the silo to the chamber, and when the device is fitted, the outlet may be located in the silo and device located at a height through a wall of the silo that is below the maximum height of granular material in the silo so that the outlet can be surrounded by the granular material. The closure may be located at, or toward, one end of the device that can be located outside of the silo, and the outlet may include a series of elongate openings in a portion of the device that can be located in the silo. The present invention may also relate to a method of installing the device according to any one of the preceding claims, wherein the method includes: forming an hole in the side wall or bottom wall of a silo, and mounting the device through the hole so that the closure is located outside the silo to allow the closure to be manually opened and closed from outside the silo for loading a fumigating agent into the chamber, and that the outlet is located inside the silo so that gas vapours of the fumigating agent in the chamber can be released to pass from the chamber into the silo When the device is fitted to the silo, the device may extend through a side wall of the silo such that the closure can be manually opened and closed, and the outlet may be located inside the silo for releasing the fumigating agent into the silo. The device may be fitted at a height through a side wall of the silo that is below the maximum height of granular material in the silo, and the device extends in a range from 0.1 to 1.5 meters into the silo and that the outlet of the device can be surrounded by granular material in the silo. Suitably, the closure of the device is within 3.5 2700655_I (GHMattm) P72404.AU.2 1407/1 I -5 metres from ground level and even more suitably within 2 metres from ground level so that an operator can load a fumigating agent into the device and remove spent fumigating agent from the device while standing on the ground or on step ladder. The present invention also relates to a method of installing the device described herein to a silo in which the method includes forming an hole in the side wall of the silo, and mounting the device to the silo so that the device extends through the hole so that the outlet is located inside the silo and that the closure is located outside the silo to allow the closure to be manually opened and closed from outside the silo. In one variant, the device may be for allowing the passage of air into or out of a silo, shed or other storage facility suitable for containing agricultural chemicals and products such as granular products and which may also be used for fumigating the silo, shed or other storage facility, the device may include: a) a passageway through which air can pass in an inward direction from outside to inside the storage facility or in an outward direction from inside to outside the storage facility; b) a chamber for receiving a fumigation agent, the chamber forming part of, or in fluid communication with, the air passageway; and c) a closure that can be opened and closed to control the passage of air through the passageway. Although the chamber may be provided separately of the passageway, preferably the chamber and passageway co-inside in, or are formed by, a single tubular structure. The passageway and chamber may have by a tubular structure having openings at opposite ends of the tubular structure and said closure is able to close one of the ends of the tubular structure. The passageway may have any cross-sectional shape and when the cross-sectional shape is circular, preferably the passageway has an internal diameter in the range of 50 to 300, suitably in the range of 50 to 200mm, and even more suitably in the range of the 80 to 120mm. 2700655_ (GHMaltes) P72404.AU.2 14107/11 In use, the fumigation agent can be located in the chamber and the closure closed, thereby allowing gas vapours evolved or released from the fumigation agent to pass into the storage facility while preventing air from passing through the passageway. The device may include a partition or divider at an outlet of the chamber that is air or gas permeable and allows gas vapour evolved or released by a fumigation agent to pass through the partition and resist the passing of the insects, bugs or granular material. Suitably, the partition or divider is a wire mesh and the mesh has apertures approximately 1.5 mm square in size. The device may include a second partition or divider capable of withstanding downward load of granular material in the silo. Suitably the second partition or divider is a convex shaped member. Even more suitably, the second partition protrudes from one end of the passageway. The closure may be a cap or lid that can be placed over one end of the passageway. The device may also include a flange extending outwardly of the device for butting against an outside surface of a wall of a storage facility. In another variant, the device may include: a tubular passageway having opposite ends; a closure in the form of a cap that is screw threadably attached to one end of the passageway; and a partition located over the passageway which is spacing from the end having said screw threaded cap, therein defining an openable chamber between the cap and the partition, and the partition having openings that allow fumigation gas to pass yet prevent granular material from entering into the passageway. In another variant, the device may be for supplying or dispensing a fumigating agent into a silo, shed or other storage facility suitable for containing agricultural chemicals and products such as grain, the device may include a chamber into which a fumigation agent can be located; a resealable opening that allows access to the chamber and through which the fumigation agent can be loaded into the chamber; an outlet that 27006551 (GHMates) P72404 AU.2 407/ I allows gas vapours evolved or released from the chamber to flow or exit from the chamber and prevent a granular, powder or particulate material to enter the chamber via the outlet. In another variant of the present invention, the invention may include a storage facility for containing agricultural chemicals or produce such as grain, wherein the storage facility includes: a) a sealed or unsealed housing or container for storing agricultural chemicals or granular material; b) one or more than one upper outlet through which air in the storage facility can exit the storage facility; c) one or more than one lower inlet through which air can enter the storage facility; and d) a chamber having an opening that can be opened and closed to allow a fumigation agent to be placed inside the chamber, the chamber also being in fluid communication with the storage facility that allows gas vapours evolved or released from the fumigation agent to pass into the storage facility; wherein the inlets and outlets include a closure means that can be operated to allow or prevent air from passing through the inlets and outlets without allowing the passage of granular material into or out of the storage facility. The lower inlet may allow air to enter or be drawn into the storage facility without a fan, blower or any other air movement means associated with the inlet. An advantage in not using a blower is that air can be drawn into the storage facility without requiring a connection to mains power. The lower inlet can also include a blower for sucking or drawing air into the storage facility. The blower may be powered by mains electricity or by an alternative power means such as: a petrol generator; a power stored in batteries that are replenished with power generated by solar panels; or by a direct supply of power from solar panels. In any event, the inlet may define a passageway through which air can enter into the storage facility. 2100655_1 (GHMaues) P72404 AU.2 14/07/11 The chamber may be in fluid communication with the inlet and when a fumigation agent is located in the chamber, the inlet may be located in a closed position. In other words, fumigation agent is prevented from flowing into the surrounding or exiting the storage facility via the inlet. The inlet of the storage facility may also have any one or a combination of the features of the device for aerating the storage facility or the device for fumigating a storage facility. In another variant, a storage facility for containing agricultural chemicals or produce such as grain may include: a) a sealed or unsealed housing for storing agricultural chemicals or grain; b) one or more than one upper outlet through which air in the storage facility exits the storage facility; c) one or more than one lower inlet through which air is drawn into the storage facility without a fan, blower or any other air movement means associated with the inlet; wherein the inlets and outlets include a closure means that can be operated to prevent air passing through the inlets and outlets without allowing the passage of granular material into or out of the storage facility. The upper outlet may or may not have a fan, blower or air movement means associated therewith. In the situation where the upper outlet does include a fan or blower, preferably, the fan or blower is power by an electric motor powered by a rechargeable battery, suitably the battery is recharged by a solar panel. In yet another variant, there is provided a method of operating a sealed storage facility suitable for containing agricultural grain, the method including the steps of: a) loading or supplying a solid fumigation agent into an enclosure in fluid communication with the storage facility so that fumes or gaseous vapour of the fumigation agent can pass from the enclosure into the storage facility for a desired period during which the fumigation agent can take effect; b) venting air into the storage facility after step a) without the use of the blower or fan feeding air into the facility; and 27006551 (GHMatter) P72404.AU.2 1407/11 -9 c) venting air out of the storage facility after step a); In other words, the step b) involves passively venting air into the storage facility without an external power source forcing air into the storage facility. Venting air out of the storage facility according to step c) may be carried out with or without air being blown, sucked, drawn or forced out of the storage facility by a fan or blower. It is also possible that a wind powered fan may assist in drawing air out of the storage facility or into the storage facility. The method may also include step d) of stopping fumes or gaseous vapour from the fumigation agent passing from the enclosure into the storage facility. Step d) may also involve operating an air valve blocking communication between the enclosure and the storage facility, and step d) involves removing the fumigation agent and/or residue thereof from the enclosure. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, of which: Figure 1 is a perspective view of a silo containing grain including a device in a bottom wall of the silo that can be used for venting or fumigating the silo and an exhaust vent in the top wall of the silo having an internal fan; Figure 2a is a cross-sectional side view of the silo shown in Figure 1, with the devices and exhaust vent opened to allow air in and out of the silo; Figures 2b is a cross-sectional side view of an alternative silo that is supported off the ground which includes devices in a bottom wall of the silo for venting and fumigating, and an exhaust vent in the top wall of the silo; Figure 2c is a cross-sectional side view of an alternative silo located on a concrete base or slab which includes devices in a side wall of the silo for venting or fumigating the silo, and an exhaust vent in the top wall of the silo; Figure 3 is a cross-sectional side view of the silo shown in the figure 1 in which the device in the bottom wall of the silo is closed for fumigating the granular material of the silo, and without the upper exhaust fan; 2700655_1 (GHMate) P72404.AU.2 14)7/ I - 10 Figures 4 and 5 are exploded perspective views of the devices fitted to the silos shown in Figures 1 to 3; Figure 6 is a cross-sectional side view of one the devices while closed; Figure 7 is a perspective view of a device according to an alternative embodiment of the invention; and Figure 8 is a cross sectional side view of a silo with inlet devices in the bottom wall and side walls of the silo and with and air movement or current represented by the direction of the arrows. DETAILED DESCRIPTION The present invention will now be described with reference to the preferred embodiments shown in the Figures. The preferred embodiments have a number of features that are the same or substantially the same and as a matter of convenience the same features have been used through the drawings to identify the same or substantially the same features. The present invention will now be described with reference to a cylindrical silo as shown in the drawings. However, it will be appreciated that the silo could be in the form of any storage facility such a shed or drum and may be any shape or size and may be used for storing any type of material including agricultural chemicals and produce. Figure 1 illustrates a silo 10 supported above the ground by four legs 11. The silo 10 is a steel vessel having top and bottom walls 12 and 13 in a frusto-conical shape and a cylindrical side wall 14. An upper hatch 15 in the top wall 12 allows granular material to be loaded into the silo 10 and a bottom hatch 16 allows material to be discharged. The upper hatch 15 may also be used for man-hole access into the silo 10. Ideally a ladder 17 and safety rail 18 to which a safety line and harness can be attached extends up the side of the silo 10. We have found that the ventilation of sealed silos 10 is important in producing high quality grain. In particular, managing temperature, moisture and water condensation inside the silo 10 are important in preventing prematuring or germination of grain which will prevent the grain from growing when sown. In addition, managing the 27006551 (GHMatiers) P72404 AU.2 1407/Il - 11 temperature and moisture in the silo reduces insect infestation and mould growth and, therefore, can help minimise the use of insecticides. Ventilation of the silo shown in Figure 1 is controlled by means of vents inlet devices 20 in the bottom wall 13 of the silo 10. The inlet devices 20 have a screw threaded cap 21 that can be manually removed to open the inlet device 20 and, thereafter replaced to close the inlet device 20. Although not shown in the Figures, it is possible for the cap 21 or any other closure means to be automatically opened and closed by an actuator that is operated based on programmable timer or in response to conditions inside or outside the silo 10. The silo 10 also includes another vent outlet 22 in the upper wall 12 of the silo 10. The outlet 22 may be any suitable outlet including conventional wind driven spinning tops 23. The outlet 22 shown in Figure 1 is a specialised wind driven top that spins when the wind blows and also includes an internal fan 23 and a butterfly valve 24 for sealing the outlet 22 when the outlet 22 is not in use. Ideally the internal fan 23 is powered by a chargeable battery (not shown) that is recharged by means of connection to an electric solar powered panel 25. Figure 2a illustrates a vertical cross-section of the silo 10 shown in Figure 1 with the inlet devices 20 and outlet 22 opened and air movement in the silo is shown by the direction of the arrows. The arrows are typical of the situation in which the side walls 14 of the silo 10 are warmer than the central region of the silo 10 and, thereby, creates circular convection currents in the direction shown in Figure 2. In addition to the convection current inside the silo 10, warm air rising in the silo 10 may also induce air to pass out of the outlet 22 and in the inlet devices 20. In the situation where wind is blowing or the internal fan 23 of the outlet 22 is operating, air will also be drawn out through the outlet 22. In either situation, air enters the inlet device 20 without external fans, blowers or alike air movement means associated with the air inlet. Figure 2b illustrates a cross-section of a silo according to an alternative embodiment of the present invention. The silo is indicative of a silo that is supported on stilts above the ground and includes inlet devices 20 and an outlet 22 that are opened. Air movement in the silo is shown by the direction of the arrows which represents the situation in which the side walls 14 of the silo are colder than the central region of the silo 10. As can be seen, colder air at the walls of the silo settles downward and moves 270D6551 (GHMar lrs)P72404.AU 2 1407111 toward the centre of the silo, together with fresh air entering from the inlet device 20 and rises upwardly in the centre of the silo. The silo also includes a wind turbine outlet 22 that draws air out of the silo when spun by wind. In addition, although not shown in Figure 2b, the wind turbine may also be fitted with a fan, such as a solar powered fan to help draw air of the silo 10 and may include an isolation valve or flap to seal off the wind turbine 22. The formation of condensation in the silo is minimised by air being drawn into the silo via inlet devices 20 and discharged from the outlet 22. Grain is discharged downwardly from the silo via the bottom hatch in the usual manner. Figure 2c illustrates a silo according to yet another embodiment of the invention. The silo of Figure 2c is essentially the same as the silo shown in Figure 2b, save for the silo being located on a concrete base or slab. The arrows in Figure 2c show the direction of air movement in the silo which is typical of the situation in which the outside air is colder that the grain at the centre of the silo. Ordinarily under these conditions, the grain can be exposed to water dripping from the ceiling of the silo. However, by allowing fresh air to enter the silo at the inlet 22 and discharging of air from the silo via outlet 22 in the manner shown in Figure 2c, the formation of condensation on the ceiling of the silo is reduced. Figure 3 illustrates a silo that is structurally the same as the silo shown in Figure 2a, however in use, the inlet devices 20 are closed and the outlet 22 has been removed to provide a fully sealed silo. Rather than removing the outlet 22, it is also possible for the butterfly valve 24 or any other suitable closure associated with the outlet 22 to be closed. In addition, Figure 3 illustrates the situation in which the inlet may be used to release or dispense a fumigating agent into the silo 10. The direction of the arrows in the silo 10 indicates the direction of the movement of the fumigating gases released from a fumigating agent in the silo 10. Further detail relating to the structure of the inlet devices 20 and how the inlet devices 20 can be used for fumigating will now be described with reference to Figures 4 to 7. Specifically, the inlet devices 20 include a tubular passageway or chamber 25 having a closure including a screw threaded cap 21 at one end and an outlet including a dome or semi-circular partition 26 at the other end of the chamber 25. The partition 26 2700655_1 (GHMaum) P72404.A 2 14/07/1i includes a series of openings 27 sized to allow the passage of the air and/or gases evolving from the fumigating agent through the partition 26 but prevent granular material from entering the chamber 25. In addition, as can be seen in Figure 5, a wire screen or additional partition 28, suitably having apertures approximately 1.5 mm square, is spaced from the screw threaded end of the passageway 25. When the cap 21 is fitted to the chamber 25; the cap 21, chamber 25 and wire screen 28 form a compartment into which a fumigating agent, preferably in tablet or solid form can be loaded and the cap closed. Suitably, the fumigating agent is in the form of a phosphide tablet that releases a phosphine gas that seeps into the silo through the chamber 25 and is circulated therein via convection currents as shown in Figure 3. It is standard practice to allow fumigating of the silo using tablets for a period of I to 2 weeks, following which residue from the tablet is withdraw from the device. Once the residue has been withdrawn, the cap 21 may be placed back on the inlet device 20 to maintain the silo 10 in a sealed state or alternatively, the cap 21 removed to allow aeration of the silo 10. The inlet device 20 also includes a collar or annular flange 29 that is fitted to the outside wall of the tubular chamber 25. The flange 29 forms a seal with the wall of the silo 10 when installed. Figure 6 illustrates a cross-section view of the inlet device 20 shown in Figures 4 and 5 installed to the bottom wall 13 of a silo 10 with a cap 21 fitted in closed position and an addition wire mesh or non-permeable membrane 30 between the compartment 31 in which the fumigating agent and the removable cap 21. An additional annular flange 32 is also provided such that the flanges are located on both the inside and outside of the silo 10. The tubular chamber 25, cap 21 and dome 26 may be made of any material including moulded metal or plastic including PVC. Preferably, the tubular passageway 25 has an internal diameter in the range of the 50 to 200mm and suitably approximately 100mm. The device may be made from any metallic materials that have been assembled together using fasteners and rivets. 2700655_ (GHMattrs) P72404 AU.2 14(07/11 -14 To installed the inlet device 20, a suitably sized hole may be cut in the side wall of the silo and the device 20 located through the opening and mounted in place such the removable cap 21 is located outside the silo and the outlet through which gas evolving from the fumigating agent may pass into the silo is located inside the silo. The device may be mounted by fastening screws or rivets that fasten the flanges of the device to the side wall of the silo. Brackets, not shown in the figures, may also be used to securely mount the device 20 to the side wall of the silo. The hole formed in the side wall for receiving the device may be located at any height, and suitably, at a height below the maximum height for storing granular material in the silo. Even more suitably, the hole formed in the side wall and the device are located in the side wall 14 and/or the frusto-conical bottom wall 13 at a height from the ground in the range of 5 metres or less, and ideally, so that the an operator and reach the removable cap 21 while standing on the ground or on a step ladder. Figure 7 illustrates a silo 10 similar to the silo 10 shown in Figure 3 with two inlet devices 20a in the bottom wall 13 of the silo 10, and in addition, two further vents or inlets 20b located in the side walls 14 of the silo 10. The convection currents in the silo 10 are such that it induces air in the silo 10 to exit the silo 10 via the vent located in the bottom wall of the silo and enter via the vents in the side wall of the silo 10. The chambers 25 of the inlet devices 20 may be of any length and may, for example, protrude into silo by a length in the range of 0.1 to 1.5meters and suitably, in the range of 0.3 to 0.5m. Figure 7 illustrates an inlet device 20 according to an embodiment of the invention comprising a tubular passageway 25 having a screw threaded cap 21 at one end and a cylindrical partition 26 at the other end of the chamber 25. The partition 26 includes a series of columns and a wire mesh having a series of openings that are sized to allow the passage of the air through the partition 26 but prevent granular material from entering the chamber 25. The columns provide structural support to the material in the silo. 27006551 (GHM&aIrs) P72404.AU.2 14/07/1 I Although not shown in Figure 7, another partition or internal wire screen, suitably having apertures approximately 1.5 mm square, is located inside the tubular chamber 25 and spaced from the screw threaded end of the chamber 25. When the cap 21 is fitted to the passageway 25; the cap 21, passageway 25 and internal wire screen form a compartment into which a fumigating agent, preferably in tablet or solid form can be loaded and the cap closed. Suitably, the fumigating agent is in the form of a phosphide tablet that releases a phosphine gas that seeps into the silo along the passageway 25 and through the cylindrical partition 26 into the silo where the gas is circulated via convection currents as shown in Figure 3. It is standard practice to allow fumigating of the silo using tablets for a period of 1 to 2 weeks, following which residue from the tablet is withdraw from the compartment. Once the residue has been withdrawn, the cap 21 may be placed back on the inlet 20 to maintain the silo 10 in a sealed state or alternatively, the cap 21 removed to allow fresh air to enter into the silo 10. The inlet 20 also includes a collar or annular flange 29 that is fitted to the outside wall of the tubular passageway 25. The flange 29 forms a seal with the wall of the silo 10 when installed. The inlet devices 20 shown in Figures 4 to 7 have essentially two modes of operation. One mode being when the cap 21 is closed and a fumigating agent inside the inlet fumigates the silo. The fumigating agent may be loaded into the device by opening the cap 21 and manually positioning a tray of the fumigating agent inside the chamber. The tray may have any specific form including a purposely formed tray of metallic or non-metallic materials, or conveniently, it is also possible to use upside down lids of containers such as lids of egg cartons, shoe boxes and alike. Ideally the inlets 20 containing the fumigating agent are located in the bottom wall 13 of the silo 10 which can be accessed by ladder or on the back of a vehicle. This avoids the standard, but somewhat hazardous practice, of climbing to the top of the silo to place fumigating on trays suspended in the silo 10. In addition, removing residue of the fumigating agent by opening the cap 21 avoids the risk of the spilling residue onto the grain inside the silo 10 and is more easily managed in terms of preventing the residue from being blown into the grain or into an operator's face. The second mode of 270655_1 I (GHMaue) P72404 AU.2 14107/11 -16 operating involves the cap 21 being removed to allow aeration of the silo 10 which can reduce the formation of condensation on the silo. One of the benefits of the preferred embodiment is the avoidance of an occupational, health and safety risk of climbing a ladder to the top of the silo for loading fumigation tablets, or unloading fumigation residue, suspended in the top space of the silo or other storage facility. The preferred embodiment enables fumigating tables to be loaded into the device for fumigating a silo and, if present, residue to be unloaded from the device without climbing the silo. Advantageously, the fumigating agent can be loaded and residue unloaded from ground level, or on small step ladder. Another benefit of the preferred embodiment is that the fumigating agent and particularly residual fragments thereof, are confined to the chamber so as not to come into direct contact with the produce within the silo. One of the problems of the tradition practice of suspending trays of fumigating agent in the top space of a silo is that the residual fragments can be spilt and, thereby contaminate material contained in the silo. The preferred embodiment minimises and possibly avoids, the risk of the fumigating agent including residual fragments thereof contaminating material inside the silo. Material contaminated with fumigating agent at low concentrations, or at any detectable amount, can render the material unusable. Those skilled in the art of the present invention will appreciate that many modifications and variations may be made to the preferred embodiment described above without departing from the spirit and scope of the present invention. For example, it is possible for the length of the passageway of the inlets to be adjustable using any suitable means such two tubular members in which one fits inside the other and can be advance and retracted as desired. According to another example, the cap may be in the form of any closure means included automated or programmable closures that open and shut as desired to allow aeration of the silo. 2700655_ I (GHD4atcrs) P72404.AU.2 14/07/11