Abstract: Containers utilizing economical gas-permeable, ultra-thin dense skin polydimethylsiloxane membranes incorporating porous substrates as passive contaminant barriers in containment systems for research, breeding, housing, and shipping of animals, including fish, birds, and mammals, and plants, or animal, plant or microbial cells. These membranes protect the animals from airborne pathogens while permitting exchange of respiratory gases and metabolic heat, as well as protect laboratory personnel, mail handlers, and others who come in contact with or transport the animals from animal borne allergens and infectious agents.

Abstract: A ultra-thin dense skin gas-controlling membrane that is impermeable to liquids, bacteria, and viruses, yet is permeable to small molecular weight gases, such as O.sub.2, CO.sub.2, NH.sub.3, N.sub.2, and water vapor, and a method for making the membrane. The membrane possesses specific gas transfer characteristic making it suitable for use in the culturing of biological materials. The membrane is incorporated into cell culture apparatus, such as roller bottle caps, for the benefit of optimally maintaining O.sub.2 and CO.sub.2 levels in the tissue culture container during all phases of cell growth. The membrane also acts as an absolute barrier to microbial contamination of the culture media within the culture container.