An　air　curtain　is　an　aerodynamic　barrier　for　regional　isolation　and　protection;　however,　research　on　its　application　in　ventilated　rooms　is　insufficient.　This　study　investigated　the　effect　of　a　recirculated　air　curtain　on　transient　contaminant　transport　when　used　inside　a　room　with　diluted　ventilation.　The　effects　of　the　discharge　air　velocity,　air　intake　position,　and　air　curtain　position　were　studied　using　a　numerical　method.　The　results　were　compared　with　those　of　diluted　ventilation　only.　The　results　showed　that　even　when　the　air　curtain　recirculated　the　polluted　indoor　air,　adding　a　recirculated　air　curtain　based　on　traditional　ventilation　significantly　reduced　the　pollution　in　the　protected　zone.　The　containment　effect　on　pollution　initially　increased　and　then　decreased　as　the　discharge　air　velocity　of　the　air　curtain　increased　from　0.5　to　4　m/s.　A　moderate　velocity　of　1　m/s　for　a　jet　width　of　0.06　m　acted　as　an　effective　aerodynamic　barrier,　with　the　average　concentration　in　the　protected　zone　reduced　by　up　to　66　%　at　600　s.　The　air　intake　of　the　air　curtain　strengthened　the　deflection　of　the　air　supply　jet　and　vortex　in　the　region.　The　air　curtain　exhibited　better　performance　when　the　air　was　recirculated　from　the　floor　below　it.　Reducing　the　protected　area　did　not　significantly　improve　the　regional　protection　capacity.　This　study　guides　the　joint　design　of　air　curtains　and　air　distribution　patterns　in　healthy　indoor　environments.(c)　2022　Elsevier　B.V.　All　rights　reserved.