Abstract: In a refrigerant system for use in cooling the interior of an insulated chamber, the system including at least one fluid reservoir and possibly one or more conduits linked thereto any or all of which may also comprise a reservoir, the system effecting the cooling by means of direct contact of the conduit with the interior of the insulated chamber whereby to achieve a desired refrigerating effect therein, the improvement comprising: insulating with insulation material the reservoir and the conduits if present, to prevent or to substantially prevent direct contact of the same with the interior of the chamber thereby providing a refrigerated barrier intermediate the interior and exterior of the chamber.