The CO emission decrease of the relative air-fuel ratio (λ = 1/ Φ = (air/fuel)actual / (air-fuel)stoichiometric) is increase from 0.76 to 1.3. There is no difference of CO emissions as hydrogen is added. For rich relative air-fuel ratios around λ = 0.8, CO emissions exhibit a maximum value, and it appears that there is almost zero CO emission above λ =1.2. the figure shows that a great quantity of CO emission are produced with the rich air-fuel mixture, since an insufficient