This relates to blow molded plastic containers wherein at least the body of such containers is of a laminated construction including, for example, a barrier layer which in the case of the container receiving carbonated products would be a gas barrier layer. It has been found that delamination does occur and this is now solved by selectively providing the container body with minute vent openings which do not extend entirely through the container body, but into that area where delamination occurs and there is an accumulation of a permeant, such as CO.sub.2. The minute vents may be formed in the exterior wall of the container either by way of piercing pins or by utilizing a laser. In the case of the piercing pins, there are incorporated in the blow mold for blow molding the container from a preform and are generally placed along the parting lines of the blow mold and also in central parts of the wall. The construction and operation of the piercing pins may be provided in several forms.