Simple DIY shop air cleaner with a activated carbon filter. I was able do this project for around $10 US Dollars. I don't have a scientific way to test how well it works or any research to back why you should do this. But I wanted to so I did!
I use common furnace filters on box fans so I can breath easy in the workshop. Lately I was thinking I could step up my air quality game by adding activated carbon filtering. Not seeing a functional way to add carbon to the box fan filters (unless I buy filters with carbon in them at extra cost.) This is what I came up with.
The parts I used were:
1 Refurbished a bathroom exhaust fan I recovered from a remodel.
2 different size plastic containers, These are empty cleaning wipe containers.
1 slightly used furnace filter I had. Filtrete MPR 1000 these are not terribly restrictive.
2 pieces of window screen, what I have is metal but I think plastic would be fine.
1 bottle of activated carbon, I bought this in the fish section of a supermarket.
Some kind of foam to make a gasket, I used drawer tool organizer liner its about 3/4" thick.
Also need: knife, marker, measuring tape, hot glue gun, screws, tape or rubber band.
Step 1: Step 1: Make Your Exhaust Fan Fit for the Job.
I recovered this exhaust fan that was removed from a bathroom remodel. The fan needed to be disassembled and cleaned because it was full of insulation. After cleaning the motor with spray contact cleaner, and the housing with a brush and towel. I wired it with a cord a simple plug then reassembled. Good as new! sorry I didn't take more pictures of this step but the process is strait forward just try and remember how you took it apart.
Step 2: Step 2: Large Particle Filter.
I use furnace filters on box fans in the work shop to keep things fresh. So the chosen victim was a gently used Filtrete MPR 1000. These are not air flow restrictive but catch a decent amount of material. Also I blow these off with the air compressor and they tolerate it well. After removing the cardboard border and marking the housing perimeter adding 1" larger on all sides to fold over. I cut out the square using scissors there is thin metal mesh so not your good scissors. . The wire mesh on the back makes it easy to fold over the edge of the housing. I used electrical tape to hold the filter in place because I did not have a rubber band large enough. I saved the rest of the filter for later replacements.
Step 3: Stpe 3: the Carbon Filter Part Thingy.
The goal is to have air travel down the center then pass thru the carbon and exit thru all the holes in the outside container.
I had 2 empty cleaning wipe bottles 1 big and 1 smaller and some foam for your gasket.
First mark and cut the lid of the larger container to fit over the exhaust of the vent fan.
Place the smaller container inside the larger one to make sure you have no clearance issues. My smaller container fit nicely inside and no trimming was needed.
Then mark the top lip of the larger container on the smaller container. This is where the top of the foam gasket will be. To make the foam gasket I just placed the large container on the foam and cut around the outside making a circle. Then place the smaller container in the center and cut around the outside of it. Now you have a foam doughnut gasket. The gasket holds the carbon between the 2 containers. After you are sure everything will fit nicely, glue the lid of the large container to the exhaust pipe on the fan.
Step 4: Step 4: How Do We Make a Filter Again??
Now with your foam collar height marked on the inside container, and everything is fitted together nicely. Cut your Screen to wrap around the OUTSIDE of the small container, and the INSIDE of the bigger one. After the screen is cut and fits nicely set it aside. Either cut or drill the inside and outside containers for maximum air flow but keeping enough material so the bottles keep there shape. I cut slots in the inner and drilled holes for the outer, I figured the slats would allow more flow volume, and the holes look nicer. Now replace the screen and glue them in place. Remember we are trying to keep the carbon in the void between the bottles.
Step 5: Step 5: Final Assembly
Now glue your foam gasket to the inner container. Cut and remove a small tab from the foam collar to make a fill port. Put the two together and fill the space between the 2 with your activated carbon. Shake as you fill to get as much in as you can. Now replace the foam piece you cut from the collar to keep all the carbon in place. Finally attach the complete bottom to the lid you glued to the exhaust port and your done. Start the fan and shake over the floor to dislodge any fine bits of carbon that may blow out. I used 1 bottle of activated carbon for this project.And I painted it
Step 6: In Closing...
I also sealed any hole the fan housing to maximize efficiency. I didn't rely on the cheap plastic snap latch's for the exhaust pipe so I screwed it together.
I found 2 main types of activated carbon, pellets and crushed pieces. Using window screen as the retainer the crushed type has lots of fine bits that blow out every time you touch the fan. I prefer the pellet type. I have better then expected airflow with this unit, the fan is quiet and rated at 110 CFM and I can feel plenty of air coming out of the holes. Maybe ill paint the tube to make it look pretty...maybe.
Future thoughts adding a timer switch would be a worth while addition.
If you have ideas to improve this design please let me know, I am always looking for ways to improve.