NOVELTY - A fuel unit (10) comprises housing containing solid fuel composition and heat producing material in which fuel composition consists of gas releasing solid material which can react to release gas when heated. Heat producing materials which can react exothermically to produce heat are disposed in thermal communication with corresponding portions of an unsegregated quantity of fuel composition such that after initiation of a reaction of each quantity of heat producing material, the quantity of heat producing material heats the corresponding portion of unsegregated quantity of fuel composition.    USE - A fuel unit for gas generator (claimed) used for fuel cell system of electric appliances, such as communication devices e.g. cellular telephones and smart phones, computers e.g. laptop and notebook computers, and navigational systems e.g. global positioning systems and book readers.    ADVANTAGE - Energy efficiency is improved, and cost of fuel unit is minimized.    DETAILED DESCRIPTION - A fuel unit (10) comprises housing containing solid fuel composition and heat producing material in which fuel composition consists of gas releasing solid material which can react to release gas when heated. Heat producing materials which can react exothermically to produce heat are disposed in thermal communication with corresponding portions of an unsegregated quantity of fuel composition such that after the initiation of a reaction of each quantity of the heat producing material, the quantity of heat producing material heats the corresponding portion of the unsegregated quantity of the fuel composition, and the corresponding portion of the unsegregated quantity of the fuel composition reacts to release a quantity of the gas. INDEPENDENT CLAIMS are included for:    (1) gas generator comprising housing and fuel units (10); and    (2) gas consuming system comprising gas consuming device and gas generator.    DESCRIPTION OF DRAWING(S) - The drawing shows an exploded schematic diagram of a fuel unit for gas generator.    Fuel unit (10)    Base (12)    Lid (14)    Array of pellets (16)    Pellets (18)