Polymer Electrolyte Membrane (PEM) fuel cells exhibit complex non-linear dynamics resulting from an exponential When the membrane water content was greater than a critical value the fuel cell current increased to a high value corresponding to an ignited state. The fuel cell current can be ignited by injection of water into the fuel cell; this hydrates the membrane which increases the current and autohumidifies the fuel cell. Spatio-temporal dynamics have been followed in the flow channels of a PEM fuel cell reactor. Co-current flow of the hydrogen and oxygen results in current ignition at the outlet of the flow channel, followed by a wave of high current density propagating toward the inlet. Counter-current flow of the hydrogen and the oxygen results in ignition at the center of the flow channels. A beautiful analogy can be drawn between water production and removal in a PEM fuel cell and heat production and removal in exothermic chemical reactors. This is an abstract of a paper presented at the AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).