A gas adsorption material containing a desired quantity of gas is placed in a pressurized container along with a product to be dispensed, and as pressure in the container is depleted during use, stored gas is released into the container to maintain pressure in the container within a predetermined range. The material may be in contact with the product, or it may be isolated from the product, and is known as a pressure swing adsorption (PSA) system, wherein adsorption of gas into the material occurs at a high pressure, and desorption of gas from the material occurs at a low pressure. Such devices are capable of storing under pressure a volume of gas 18 to 20 times the volume of the material. A preferred adsorbent gas storage material is granular activated carbon, or a carbon fiber composite molecular sieve (CFCMS). Other materials, such as zeolite, starch-based polymers, activated alumina, silica gel, and sodium bicarbonate, or mixtures thereof, may be used, although they generally are not as effective as activated carbon. The adsorbent material may be in granular, powdered, or pellet form, or a mass of the material may be formed into variously shaped cohesive bodies, such as balls, tubes, cubes or rods, or sheets or screens which may be flat or curved or folded into various shapes, such as, for example, an accordion-like fold.