NOVELTY - A fuel source (24) comprises a housing having an outlet (53); a vapor transmission elements (46) having a portion in the housing defining a cavity (50) and having a perforated outer surface defining an opening (52) in fluid communication with the cavity; and a fuel in the housing. The fuel is in fluid communication with the outlet through the opening and the cavity of the vapor transmission elements.    USE - For fuel cell.    ADVANTAGE - The vapor transmission elements is capable of providing a high surface area, relatively constant interface with the fuel, thus providing relatively constant delivery of fuel. Furthermore, the high surface area interface, combined with delivery of fuel in the gas phase, enhances the geometric and orientational versatility of the fuel source. Vapor phase fuel delivery can also reduce migration of the fuel from the anode to the cathode e.g. methanol crossover, which can cause parasitic loss and reduced runtime and mixed potentials at the cathode and reduced output power. What is more, the fuel source is capable of providing these features in a low volume design with good protection against leaks. The fuel cell system having gas mover(s) actively regulates flow of the gas phase fuel and further enhances the performance of the system. Also, since vapor transmission elements can contact fuel, the interface between the vapor transmission elements and the fuel can remain relatively constant e.g. the fuel does not recede from the vapor transmission elements. As a result, as fuel is consumed during use, fuel source is capable of maintaining a constant fuel delivery rate, thereby allowing fuel cell stack to provide a constant power output. Moreover, fuel source is capable of providing the above features in a relatively simple e.g. no moving parts, low volume design with good protection against leaks, particularly when fuel includes a gel. The restrictive mechanisms partially or completely reduce e.g. isolate gas flow from and to fuel source, thus reducing degradation of fuel e.g. oxidation by air and unnecessary evaporation of fuel.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a fuel cell system; and    (2) a method of operating the fuel cell system.    DESCRIPTION OF DRAWING(S) - The drawing shows the fuel source.    fuel source (24)    vapor transmission elements (46)    cavity (50)    opening (52)    outlet. (53)