A new exclusion process for CO and CO₂ from ammonia synthesis gas has been proposed: this takes place at room temperature and atmospheric pressure. The process is based on the electrochemical reduction of CO and CO₂ to methanol proceeding at a mediated electrode via homogeneous catalysis. The maximum percentages of CO and CO₂ excluded from the initial gas were about 1.5 and 4.1%, respectively, with a mediated electrode of 82.8 cm² area in a reaction time of 5 h. The amount of excluded CO and CO₂ was equivalent to the sum of moles of methanol formed and gases dissolved into the solution alone. The electroreduction of CO and CO₂ was more efficient at three-phase (electrode/solution/gas) and at two-phase (electrode/solution) interfaces, respectively.