A multilayer web article, including a first layer of a porous material, e.g., Tyvek.RTM. film, and a second layer overlying and sealed to the first layer. The second layer is non-porous to passage of gas therethrough and includes a peelable film, e.g., of polyethylene, in contact with the first layer of porous material. The peelable film permits peeling removal of the second layer from the first layer to expose the first layer of porous material for passage of gas therethrough. In a specific construction, the web article constitutes one of opposedly facing panels of a lay-flat bag article, in which the facing panels are bonded to one another along superposed edges thereof. After pressurization integrity testing of the bag, the peelable film is peeled away to enable steam - and/or ETO-sterilization of the bag and its contents to be carried out.