The catalytic ignition of dry carbon monoxide and air in a planar stagnation-point flow over a platinum foil is studied in this paper. The heterogeneous reaction mechanism is modeled with the dissociative adsorption of the molecular oxygen and the nondissociative adsorption of CO, together with a surface reaction of the Langmiur-Hinshelwood type and the desorption reaction of the adsorbed product, CO2(s). The critical conditions for the catalytic ignition are deduced using high activation energy asymptotics of the desorption kinetics of the most efficient adsorbed reactant, CO(s). When using the appropriate activation energy of the desorption reaction of CO(s), the ignition temperature obtained in closed form compares very well with experimental results.