1 CH_4 + 2 O_2 -> 1 CO_2 + 2H_2O So the amount of CH4 and CO2 is the same in number of molecules, which also means they are the same volume of gas (at low pres

1 CH_4 + 2 O_2 -> 1 CO_2 + 2H_2O So the amount of CH4 and CO2 is the same in number of molecules, which also means they are the same volume of gas (at low pressures). Of course the mass of CO2 is about three fold but that doesn't mean much.