Leaking　safety　is　an　issue　preventing　air　conditioner　using　R290　from　being　widely　used,　and　ventilation　is　an　effective　method　to　improve　leaking　safety　of　integral-type　air　conditioner.　In　this　paper,　the　concentration　of　leaking　refrigerant　of　integral-type　fresh　air　air　conditioner　was　studied　experimentally,　combined　with　CFD　simulation,　and　the　leaking　safety　was　evaluated.　Results　show　that　due　to　the　dilution　of　supply　air　flow,　in　the　location　with　highest　concentration,　namely　supply　air　outlet,　no　higher　concentration　than　LFL　is　monitored.　However,　there　still　exists　the　possibility　of　combustible　region　in　the　indoor　unit.　Moreover,　fresh　air　contributes　to　remarkable　decrease　of　refrigerant　concentration　after　leakage　with　a　decrease　rate　as　high　as　15.　6%　LFL　/　h.　Therefore,　the　main　research　spot　should　be　fixed　on　the　prevention　of　ignition　source　inside　the　indoor　unit.　This　paper　is　helpful　for　having　a　knowledge　of　leaking　rules　of　integral-type　fresh　air　air　conditioner　and　provides　a　reference　for　the　design　of　air　conditioner　using　flammable　refrigerants.　©　2024　Beijing　University　of　Technology.　All　rights　reserved.