You could buy one of these:
It should give you some idea of the complexity of doing it safey.
http://www.siamwaterflame.co.uk/html/hd_350__oxy_hydrogen_generator.html
It should give you some idea of the complexity of doing it safey.
http://www.siamwaterflame.co.uk/html/hd_350__oxy_hydrogen_generator.html