In　this　study,　explosion　venting　of　front,　centrally,　and　rear　ignited　9%　methane-air　mixtures　has　been　conducted　in　a　1-m(3)　rectangular　vessel　with　and　without　cylinders　placed　parallel　to　the　venting　direction.　Three　pressure　peaks　P-1,　P-2,　and　P-ext　caused　by　vent　failure,　flame-acoustic　interaction,　and　external　explosion,　respectively,　can　be　distinguished.　The　pressure　peak　P-1　appears　in　all　the　tests　and　is　insensitive　to　the　ignition　position,　but　the　existence　of　obstacles　increases　its　value.　The　pressure　peak　P-2　only　appears　in　the　centrally　and　front　ignited　explosions　without　obstacles.　The　pressure　peak　P-ext　can　be　observed　in　the　rear　ignition　tests　and　is　strengthened　by　the　cylinders.　The　duration　of　the　Helmholtz　oscillations　is　longer　in　front　ignition　tests,　whereas　addition　of　cylinders　had　a　minor　effect　on　their　frequency.　This　study　also　validates　the　ability　of　FLACS　in　predicting　a　vented　methane-air　explosion　by　comparing　the　simulated　pressure-time　histories　and　flame　propagations　with　experimental　results.　FLACS　can　basically　predict　the　shape　of　overpressure　curves.　If　cylinders　exist,　the　simulation　results　ensure　better　agreement　with　the　experimental　data　because　FLACS　cannot　simulate　the　flame-acoustic-interaction-induced　pressure　peak　P-2.　The　performance　of　FLACS　is　satisfactory　in　rear　ignition　tests　because　it　calculates　P-ext　and　obstacles＇　effect　on　P-ext　exactly.　The　flame　behavior　simulated　by　FLACS　is　similar　to　that　in　experiments,　but　the　effect　of　the　Taylor　instability　on　the　flame　is　not　sufficiently　considered.