NOVELTY - A gas generation arrangement (10) comprises an initiating element (16) (e.g. a semiconductor bridge) in operable communication with a heat generating material (22); a gas evolution material (26) in reactive communication with an activity caused by the heat generating material; and a barrier (24) between the heat generating material and the gas evolution material.    USE - Used as a pyrolytic gas generation/evolution arrangement, used in a portable power source containing a fuel cell and a control having sensor(s) (claimed), and particularly for providing hydrogen fuel to a fuel cell to generate electricity.    ADVANTAGE - The gas generation arrangement operates to evolve the target gas without the operational parameter of hyperbaric pressure, thus facilitating an ergonomic shape capability of the arrangement. This shaping of arrangement allows the user to carry the arrangement comfortably and in a streamlined manner. The arrangement can generate electricity in a small, lightweight and efficient power source. The initiating element provides a high temperature by utilizing a very small amount of energy. The barrier allows greater control over the gas evolution rate. The gas evolution material remains stable over time, even after heating, hence gas generation from the arrangement can be stopped at any time by removing the thermal input, and the gas evolution material can be packaged as a clip, that can be replaced in the arrangement. Thus, the gas generation and electric energy can be provided for extended periods by swapping the clips of the gas generation material.    DETAILED DESCRIPTION - The barrier modifies the heat output from the heat generating material, causing the gas evolution material to evolve a target gas. The gas evolution material is responsive to heat energy, water vapor or sub-atmospheric pressure.    An INDEPENDENT CLAIM is included for a barrier for the gas generation arrangement.    DESCRIPTION OF DRAWING(S) - The figure shows an exploded perspective view of a gas generation arrangement.    gas generation arrangement (10)    initiating element (16)    heat generating material (22)    barrier (24)    gas evolution material (26)    gas evolution material holder. (30)