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4.2          Care should be taken even after a CTU has been declared as ventilated. Gas can be held in packages of  of cargo, then desorbed over a long period of time, even over many days, raising the level of gas inside the cargo transport unit to above the safe exposure level. Bagged cereals and cartons with large air spaces are likely to produce this effect. Alternatively, gas and the fumigant sachets or tablets can become 'trapped' at the far end of a CTU by tightly packed cargo.

4.3          In reality any CTU that has carried dangerous or fumigated goods should not be considered as safe until it has been properly cleaned and all cargo residues, gaseous and solid, have been removed. The consignee for such goods should have the facilities to carry out this cleaning process safely.

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