This　study　investigates　the　effect　of　the　ignition　position　on　vented　hydrogen-air　deflagration　in　a　1　m(3)　vessel　and　evaluates　the　performance　of　the　commercial　computational　fluid　dynamics　(CFD)　code　FLACS　in　simulating　the　vented　explosion　of　hydrogen-air　mixtures.　First,　the　differences　in　the　measured　pressure-time　histories　for　various　ignition　locations　are　presented,　and　the　mechanisms　responsible　for　the　generation　of　different　pressure　peaks　are　explained,　along　with　the　flame　behavior.　Secondly,　the　CFD　software　FLAGS　is　assessed　against　the　experimental　data.　The　characteristic　phenomena　of　vented　explosion　are　observed　for　hydrogen-air　mixtures　ignited　at　different　ignition　positions,　such　as　Helmholtz　oscillation　for　front　ignition,　the　interaction　between　external　explosion　and　combustion　inside　the　vessel　for　central　ignition,　and　the　wall　effect　for　back-wall　ignition.　Flame-acoustic　interaction　are　observed　in　all　cases,　particularly　in　those　of　front　ignition　and　very　lean　hydrogen-air　mixtures.　The　predicted　flame　behavior　agree　well　with　the　experimental　data　in　general　while　the　simulated　maximum　overpressures　are　larger　than　the　experimental　values　by　a　factor　of　1.5-2,　which　is　conservative　then　would　lead　to　a　safe　design　of　explosion　panels　for　instance.　Not　only　the　flame　development　during　the　deflagration　was　well-simulated　for　the　different　ignition　locations,　but　also　the　correspondence　between　the　pressure　transients　and　flame　behavior　was　also　accurately　calculated.　The　comparison　of　the　predicted　results　with　the　experimental　data　shows　the　performance　of　FLACS　to　model　vented　mixtures　of　hydrogen　with　air　ignited　in　a　lab　scale　vessel.　However,　the　experimental　scale　is　often　smaller　than　that　used　in　practical　scenarios,　such　as　hydrogen　refueling　installations.　Thus,　future　large-scale　experiments　are　necessary　to　assess　the　performance　of　FLACS　in　practical　use.