In the study the lift-off, blow-out and blow-off stability limits of hydrogen/propane flames and hydrogen/carbon dioxide flames were tested in three different mixing arrangements. The first was to premix hydrogen with carbon dioxide or propane to form a jet flame. The second was to add the gas as an annular jet around the hydrogen flame. The third was to inject into the centre of the hydrogen flame. Propane and carbon dioxide have the same density but create very different chemical kinetic changes when added to hydrogen flames. The results showed that when premixed with hydrogen, propane is more effective in flame lift-off and blow-out. The analysis of kinetic mechanisms revealed that the propane is the dominating fuel in determining the burning rate of the hydrogen/propane while carbon dioxide mainly acted to dilute the hydrogen/CO2 mixture. Comparing the three mixing arrangements, the experiments showed that hydrogen flame can be effectively lifted or blown out when gases were in annular flow around the hydrogen flame. The isothermal mixing process of the co-flow configuration was discussed. (c) 2006 Elsevier Ltd. All rights reserved.