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.