Operating principle：

Use the designed structure,to effectively prevent sand dust and rain from entering the room,and ensure high-efficiency ventilation performance. When the wind drives sand and rain into interior of the shutters,they will enter the first chamber. The structure will effectively blocks large particle of sand dust and raindrop.For fine sand dust and raindrop suspended in the air flow,they will follow the air to move in a curve inside the blinds. Then they come into the second chamber, and will be effectively blocked again through the structure.For the isolated sand dust and rain,they will fall freely and be effectively discharged to outside through the inclined opening on the bottom.