For this super-fast and easy life hack, all you need is a window and a mini fan.
Step 2: Window
Just open your window up wide enough so that it can fit the height of your fan.
Step 3: Last Step
Now, carefully place your fan inside the window. The fresh air will be new and not used air going into the fan unlike if you shut the window and let the fan stay in the room. This works better with small rooms, as regular fans usually do.