Hi friends, My air conditioner is a split one (it has 2 parts: one inside the house and the other outside). It has 4 modes of operation: cool, fan, and 2 other modes. My question is that what does the machine really do in the fan mode? I wonder whether it just serves as a normal fan (which means it just circulates the air inside the room), or it can help exchange the air inside the room with the outdoor air? Thanks for reading my question. Riscilla.