Do I look cuter if I tilt my head to the side mum? 🥺 Source: aribabyxo on catpictures.
This works best if you keep windows closed.
Another design is using 2 20x25x1 filters, taping them to the sides of the box fan and then to each other so they sort of make a triangle, then cutting cardboard to make a top and bottom to the triangle.
This was discovered as a more effective design during the 2020 US west coast fires.