A fuel system including a fuel cell including a plurality of unit cells supplied with a prescribed gas to generate electricity, a stoichiometric ratio calculating apparatus calculating the stoichiometric ratio of the prescribed gas for each unit cell, and a gas flow increasing apparatus increasing the supply of the prescribed gas when the stoichiometric ratio falls below a prescribed value. A cylindrical apparatus having first and second surfaces of either planar or arcuate configuration is configured with plural polygonal openings useable for manipulation of the apparatus or as openings into which various modules may be set to increase the activity versatility of the apparatus. The device is configured to satisfy the relationships A=swept volumearea of heater element=8 to 14 microns; and B=firing chamber volumeswept volume=2 to 6.