Abstract: A container lid for packaging principally air contaminative products comprises a generally circular body with a main central portion and a downwardly extending peripheral lip portion adapted to snap over and engagedly receive the top rim portion of a container in sealed relationship; the underface of the main central portion terminates at the periphery thereof with an upstanding side wall contiguous with the lip portion; the side wall has an upper peripheral portion inwardly spaced from and defining with the lip portion a receiving portion for the rim portion of the container and a lower peripheral portion provided with a series of radially inward and circumferentially spaced air and fluid outlet cavities extending to the underface of the main central portion so that air and fluid expulsion from the container may be allowed even after the lower peripheral portion of the side wall has contacted the rim portion of the container; as the container lid is further pressed down into the container, the upper peripher