Combinations of atmosphere control members are used to control the atmosphere within a sealed container which contains a respiring biological material. The combination makes use of a first ACM having a first R ratio (the ratio of carbon dioxide permeability to oxygen permeability) and a second ACM having a second R ratio, the first R ratio being substantially greater than 1.0, and the second R ratio being less than the first R ratio. This combination (31, 321, 322, 331, 332) can form part of the sealed container (1) itself, or can be part of an assembly (31, 32, 34) through which the packaging atmosphere within the sealed container (1) is circulated.