Making a Corsi-Rosenthal cube

An idealized depiction of the Corsi-Rosenthal cube described

Materials

• One box fan (20" x 20" / 50cm x 50cm is common)

• Four ≥ MERV 13 furnace filters, close to the box fan in size

• Duct tape

• Scissors

• Spare cardboard

In this design, polluted air is sucked in through the filters on the sides of the cube and clean air is blown up out of the top. Blowing upward substantially increases air mixing in the room, ensuring that the room's air is cleaned faster.

Steps

1. Tape the filters into a cube shape, pointing the arrows on the edges of the filters inward

   • The arrows indicate air flow direction

2. Tape a sheet of cardboard to the bottom to cover it

   • Using one of the large faces of the box fan's box is common

3. Tape the box fan to the top, such that it blows upward away from the cube

   • Watch for the cord - if necessary you may need to construct a pass-through for it, which should be sealed well with tape to prevent unfiltered intrusion

4. Totally close all seams in the construction with duct tape

5. Cover the corners of the fan's face

   • This prevents unfiltered air from circulating through the fan, because box fans will draw air in at their corners (where the blades don’t reach)

   • A popular solution is to cut a circle shroud out of the other large cardboard face from the box fan box, but you can also just tape over the corners and edges - some coverage of the blades is preferable to leaving any of the void space uncovered

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