This　paper　investigates　the　pressure　evolution　and　flame　propagation　behavior　during　the　vented　explosion　of　H2/air　mixtures　with　hydrogen　concentrations(C)　ranging　from　9　%　to　27　%.　The　experiments　were　conducted　in　a　1　m3　vessel　equipped　with　a　vent　covered　by　a　4-mm　thick　hinged　aluminum　panel.　The　results　reveal　three　distinct　internal　pressure　peaks　during　the　vented　explosion:　P1　(the　first　pressure　peak),　P2　(the　second　pressure　peak),　and　P3　(the　third　pressure　peak).　When　C　exceeds　12　%,　P2　replaces　P3　as　the　highest-pressure　peak　within　the　vessel.　As　C　increases　from　9　%　to　27　%,　P1　becomes　less　distinguishable　in　the　pressure　profiles.　The　maximum　pressure　formula　proposed　by　Cubbage　and　Marshall　accurately　predicts　the　maximum　explosion　overpressure　(Pmax)　within　the　vessel.　In　the　external　pressure　profiles,　a　maximum　external　pressure　peak　(Pext)　is　observed.　As　C　increases,　Pext　rises　from　4.8　kPa　at　C　=　15　%　to　49.9　kPa　at　C　=　27　%.　Additionally,　as　C　increases,　the　maximum　external　flame　speed　increases　from　170　m/s　at　C　=　21　%　to　236　m/s　at　C　=　27　%.　When　C　increases　from　18　%　to　27　%,　the　maximum　external　flame　length(Lmax)increases　from　1.5　m　to　2.0　m.　During　the　inertia-free　venting　experiments,　the　fireball,　synchronized　with　the　external　explosion,　assumes　a　mushroom　shape.　When　hinged　panels　are　used,　the　fireball　becomes　progressively　flatter　at　the　vent　as　C　decreases.