The invention provides a substantially air impervious package in the form of a laminated plastic film bag (10). The bag (10) has a substantially air impervious wall (12) defining a cavity (14) for receiving an article to be packaged. Non-return valve means (16) in the form of an adhesive film layer (15) on which is deposited a silicone sealant type material (19) which has resiliently deformable or elastic properties, and on which is provided a porous layer (17), is provided on an inner surface (18) of the wall (12). The valve (16) sealingly bonds with the laminate plastics material of the bag (10).
