Clean burning nature and renewability of hydrogen makes it viable and alternative/supplementary fuel for utilization in IC engine. In the past two decades, researchers have gained interest in using hydrogen in Internal combustion (IC) engines. Electrolysis is the widely used technique for production of hydrogen. The effect on emission parameters of using hydrogen and HHO gas in a dual fuel engine at idling condition was focused in this research work. HHO gas was synthesized from stored cylinders of hydrogen & oxygen in 2:1 ratio. The mixture of H2 and O2 are produced in stoichiometric ratio similar to electrolysis of water. Effect of introduction of hydrogen gas and stimulated HHO gas on emission characters such as unburnt hydrocarbon (UHC), carbon dioxide (CO2), oxides of nitrogen (NOx) and smoke of the engine were noted at idling condition (1700 rpm). Engine was supplied with 6, 12, 18, 24, 30, 36 LPM of hydrogen and 9, 18, 27, 36, 45, 54 LPM of HHO gas where the composition of mixture was maintained in the ratio of 2:1 and energy supplied by Hydrogen and HHO gas remains same. Introduction of hydrogen and HHO gas has reduced the total diesel fuel consumption and formation of CO2 at all operating condition than neat diesel operation. There was slight increase in UHC emission with hydrogen and by substituting HHO gas the UHC emission was reduced. © Published under licence by IOP Publishing Ltd.