ROOM AIR FILTER

This inexpensive DIY room air filter is easily made out of a cardboard box, an air filter, and a fan.

It can be more effective than a commercial HEPA filter, filtering out smoke particles, dust, pollen, cat dander, etc, while also reducing exposure to COVID-19.

Materials Needed

• 1 MERV-13 filter ** (see final step for more info.)
• 1 table/desk fan
• 1 cardboard box
• packaging tape or duct tape
• Scissors / utility knife
• glue or heat gun

Firstly, decide what size box/air filter you want. These will also depend on the fan you choose. It's best to consider the room size, box size, air filter size, and type of fan to use together, as they are interdependent.

The following describes the one I made, including the specifications of material I used to make the room filter. Yours can vary significantly.

Specifications:

• 1 MERV-11 filter (15" x 20" x 1")
• 1 cardboard box (approx. 9" x 16" x 24")
• 1 table/desk fan as shown
• 1 cylindrical cardboard "building form". (8" diam. x 10" long)

Note: The cylindrical cardboard "building form" is not a requirement, but worked well in this project because it fit perfectly onto the fan. The form is available at Lowe's, Home Depot, or other building supply stores in longer length. You will need to cut it shorter, however it could be eliminated if using a bigger box and a different fan.

Instructions:

• Cut a square or rectangular opening on the bottom side of the box where the filter is to be placed.
• Tape the top side of the box closed. Then optionally you can flip the box over and glue the inside flaps down to give more support to the box, making it sturdier and more rigid.
• Place the cylindrical cardboard "building form" on the center of the box and trace the diameter of the form on the box. Remove the form and cut a hole in the box the size of the form diameter.
• Fit the form into the hole slightly. Glue the form to the box. When the glue is dried you can also add tape if desired, but may not be needed.
• A slit will also have to be cut in the form to fit the fan. See photos. Alternatively, you could remove the base of the fan eliminating the need to cut a slit in the form. The choice is yours. And, of course, your choice of fan may be different.
• Hold the box up to a light to see if all the seams are sealed. Add glue or tape if needed.
• Tape the air filter over the open side of the box noting the direction of air flow by the arrow on the filter. The filter air MUST flow in the same direction as the fan's air flow.
• Attach the fan over the form. Tape them together if needed. Again, ensure all the seams are sealed.

The filter is complete.

This air filter is a simple, inexpensive, and can be more effective than a commercial HEPA filters.

For more information on the topic, I recommend reading about the Corsi-Rosenthal box fan filter.

** A higher MERV rating often means smaller particles or particulates collected, but lower airflow, which can cause the fan to work harder, and possibly run at a higher temp.

What is a MERV rating: https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating