Oxyhydrogen is an alternate name for HHO, hydroxy gas, Brown's gas, etc.
Oxyhydrogen will combust when brought to its autoignition temperature. For a stoichiometric mixture at normal atmospheric pressure, autoignition occurs at about 570 oC (1065 oF).
At normal temperature and pressure, oxyhydrogen can burn when it is between about 4% and 95% hydrogen by volume.
When ignited, the oxyhydrogen gas mixture converts to water vapor and releases energy, which sustains the reaction.
A pure stoichiometric oxyhydrogen mixture may be obtained by water electrolysis, which uses an electric current to dissociate the water molecules.