Abstract: The present invention relates to an emissions reduction system to reduce levels of NOx and/or particulate matter from combustion engine emissions. The system comprises a feed water reservoir, an electrolytic cell capable of converting water into substantially pure hydrogen and oxygen and water vapour. A gas bubbler is provided to prevent build-up of hydrogen and to act as a flame arrestor from the combustion engine. The hydrogen produced by the electrolytic cell is fed via the gas bubbler into an internal combustion engine.