Dear Crispin (in Canada?), Thank you for the correction, always welcome. I can't follow Andy's figures for the stoichiometric volumes. C2H2 + 2.5 O2 = 2CO2 + H2O eg 2.5 volumes oxygen for 1 volume of acetylene C3H8 + 5 O2 = 3 CO2 + 4 H2O eg 5 volumes of oxygen for 1 volume of propane Regards, Peter