referring to fig1 , one embodiment of the invention comprises a portable support tray 1 for receiving a freight container . the tray has a floor 2 , inwardly inclined sides 3 , a central conduit 4 and four upwardly extending legs 5 . the conduit 4 is open at one end 6 so that it is able to receive a flow of air and also has a series of vents 7 along its length to enable the flow to be distributed across the floor 2 . referring to fig2 , when the tray is in use an iso grade freight container 8 may be placed on the legs 5 so that there is a space between the underside of the container and the floor 2 of the tray . the container 8 is covered by an air impermeable flexible enclosure 9 and this may be sealed to the tray . a flow of hot air is applied to the opening 6 of the conduit so that the air is driven along the conduit and distributed over the floor 2 of the tray via the vents 7 . as the vents are relatively small the conduit 4 serves as a pressure accumulator for the hot air . the air moves to the edges of the tray 3 and then upwards around the ends , the sides 10 and roof 11 of the container . the inward incline of the sides 3 of the tray helps direct the flow of air upwards to substantially prevent it from escaping from the confines of the enclosure 9 . preferably the arrangement is such that when the air is flowing there is a space of approximately 100 mm between the ends , sides and roof of the container and the enclosure 9 . in some embodiments a supplementary flow of hot air may be circulated into and out of the enclosure via openings 9 a and 9 b . the hot air causes the external faces of the container to heat up and this kills at least most undesirable life forms at or adjacent to those faces . in preferred forms of the invention the air flow is set so that the container is heated to 56 ° c . to 60 ° c . and is maintained at that temperature for 30 minutes . the temperature chosen in any one situation may vary depending on the sensitivity of the contents of the container , if any . higher temperatures may be applied to empty containers and in such cases the treatment time may be reduced . for example in cases where an empty container is heated to 85 ° c . the treatment time may be reduced to approximately 5 minutes . in preferred embodiments of the invention the tray 1 is heated , to approximately 56 ° c . to 60 ° c . prior to placing the container on the tray . this assists to prevent at least some insects or other pests from escaping the decontaminating heat as they may otherwise detect a slowly increasing temperature and try leave the vicinity of the container before temperatures rise to a level sufficient to kill them . heat applied to the exterior surfaces of the container conducts through to the interior of the container . in some embodiments of the invention the amount of heat conducted is sufficient to decontaminate the inside of the container . fig3 , 4 and 5 show a portable decontamination chamber 12 according to an alternative embodiment of the invention . referring to fig3 , the chamber has a support tray 13 comprising upper and lower rigid floor sheets arranged so that there is a space between them . the chamber also has an inwardly inclined forward side 14 and a series of legs 15 . the space between the floor sheets provides a pressure accumulating conduit and there is a series of vents 16 spaced along the upper floor sheet to distribute a hot air flow across the upper surface 18 of the tray . the conduit has an opening 17 situated mid - way along the tray adjacent to its forward side 14 for receiving the air flow . vent holes ( not shown ) are also situated at the edges of the tray 13 , both at the upper surface of the tray and at the vertical sides of the tray , to allow the air flow to proceed therefrom and create a hot air curtain at the edges of the tray . the hot air curtain makes it difficult for certain life forms to escape the confines of the chamber . the chamber also has an enclosure comprising a rigid rear side wall 19 , rigid end walls 20 and a frame 21 . the frame 21 is arranged to pivot about hinges 22 so that it can provide a roof and front side structure . fig4 shows the chamber when a 40 foot iso grade freight container has been placed on the feet of the tray . the frame 21 has been swung down by way of the hinges and is ready to support an air impermeable flexible curtain 23 which is illustrated in a rolled - up or stowed disposition . referring to fig5 , when the chamber is ready for use the curtain 23 is rolled down over the frame so that the container is completely enclosed . with the container in this situation hot air is pumped into the conduit space within the tray and from there the air moves around the floor , sides and roof of the container to kill undesired life forms , for example microbes , insects or rodents on or immediately adjacent to the exterior of the container . in some embodiments heat from the air also conducts through the walls of the container to decontaminate its interior . the temperature , the treatment time and the spacing between the container and the chamber may be the same as described for fig1 and 2 . preferably the tray of the fig3 , 4 and 5 embodiment is heated prior to locating the container within the chamber for the same reason described previously . fig6 illustrates two portable decontamination chambers similar to that described for fig3 , 4 and 5 , except that the flexible curtain in each case comprises two rolls 24 , 25 rather than one . in this embodiment an air supply pipe 26 is arranged to direct a flow of hot air from the conduit into open doors 27 of the container to heat and thus decontaminate the inside of the container . preferably the tray for the fig6 embodiment is heated prior to locating the container within the chamber for the same reason described previously . in some embodiments of the invention a supplementary flow of hot air may be applied to the chambers of fig3 to 6 through a side wall of the enclosure . in further embodiments of the invention the flow of hot air carries decontamination chemicals such as pesticides and / or water vapour . in such cases these may combine with the heat in the air to kill undesired life forms . in some embodiments of the invention the inside of the - container may be heated by way of heat ( eg hot air ) applied to exterior surfaces of the container , and the space within the container is subjected to a chemical fumigant arranged such that raising temperature within the container increases the efficiency of the fumigant . in this embodiment hot air is circulated around the outside of the container ( ie without fumigant ) and the fumigant is only applied within the container . in preferred forms of the invention the hot is allowed to vent from the enclosure / chamber to be replaced by new hot air , rather than recirculating used air . this can facilitate control of humidity within the enclosure / chamber . to achieve container temperatures sufficient for decontamination the hot air applied to the container may be at up to 200 ° c ., but preferably from 75 ° c . to 175 ° c ., and most preferably from 80 ° c . to 150 ° c . the air may be driven at up to 1 , 000 m 3 / min , preferably between 200 m 3 / min and 750 m 3 / min , and most preferably between 250 m 3 / min and 500 m 3 / min . preferably humidity within the enclosure / chamber is at 5 % to 50 %. as will be appreciated , the portable nature of the tray and chambers described above means that they can be readily moved from one location to another , for example from one port or wharf to another . in some embodiments the tray or chambers may be mobile , for example they may have set of wheels and a motor to power these . while some embodiments of the invention have been described by way of example it should be appreciated that modifications and improvements can occur without departing from the scope of the following claims .
a method of decontaminating a freight container comprising the steps of : a ) placing a freight container on a support ; b ) using an enclosure to substantially enclose the container on the support ; and c ) applying heat so that hot air moves within the enclosure around at least upright ends , sides and a roof of the container to kill or substantially weaken undesired life forms on or immediately adjacent to the exterior of the container .