Activated Carbon Air Filter

This instructable shows you how to make an air purifier to filter pollutants such as tobacco smoke, solder fumes and many other organic materials out of the air that you breathe.

Step 1: Needed Materials and Basic Idea

Computer fan
Activated Carbon
Glue
Window screen
pantyhose
Modeler's plywood
Basswood or balsa
12 volt AC/DC converter

If you have enough modeler's plywood, then you can make the frame out of that, but to save money, I chose to glue my frame together with some balsa wood I had. I had everything but the activated carbon, which you can purchase at pet stores, already at my house.


The purifier works by drawing air through the carbon and forcing it out through the top. The picture below is a cutaway view. The carbon surrounds the purifier on four walls with the fan on the top. The large surface area allows the air to pass through slowly which cleans the air much better.

Step 2: Make the Frame

This part is critical since it is what keeps your filter from falling apart, so cut and glue well. For the edges of the walls, I used 1/4x1/4 inch strip of balsa. To support the middle, I used 1/8x1/4 inch strip of balsa. Next, make 4 of both the inside and outside walls. You may need to cut some small squares of paper to stick in the corners for extra support.

After the walls dry, lay the window screen out on wax paper. Apply a thin strip of glue to one side of each wall and place onto the window screen. The wax paper will keep the glue, which will run through the screen, from sticking to your table.

After the glue dries, cut each wall away from the sheet of window screen.

Next, cut a 45 degree angle in two sides of the wall so that the four outside and four inside walls can be joined to each other. Make sure that the window screen is on the outside of the square. In the end, you should have two squares with four walls covered and two left open (for the top and bottom of the filter).

Step 3: Putting It All Together

Now that you have the two frames made, you can put everything together. But before you do this, make sure you slide pantyhose over both frames. This will keep the smaller bits of carbon from falling out.

Now, take the bottom part of the filter and glue the frames to it.

While that dries, clean the carbon. During shipping, small bits of dust will fall off. Clean it by placing it in a colander and running water through it. Let it dry and pour it into the filter.

Next, once its full, glue the top on. NOTE: the small hole in the top is used for adding or removing activated carbon after the top is glued on. I just put tape over this to keep the carbon from falling out

If all was done correctly, the fan should fit perfectly into the remaining hole in the top of the filter. Glue the fan in place and you now have a finished air filter.

Step 4: Finish It Up

The white tube on the top of the filter is there to help spread the filtered air around the room. To make it, all you have to do it tape together a paper tube that will fit over the fan. The top is made by cutting vertical slits in the tube and overlapping them to make the paper fold over the top and deflect the air into the room.

To turn it on, you take the two computer fan leads and solder them to the 12 volt power supply. If everything works, it will be very hard to hear it running.

Lastly, if you want the filter to emit a fragrance into the room, it is very simple. Place your favorite liquid fragrance into a thin medicine bottle and tape it to the center of the fan. As the air from the fan passes the medicine bottle, it will pull the fragrance out of the bottle and into the air.


Now, the only problem with the filter is that the air emitted has a slight smell of carbon and I am not sure how to get rid of this. Since the fan cannot develop a lot of pressure, forcing the air through another filter would be difficult. If you have ideas then feel free to email me.

Comments

[gggonzalez]

I built something very similar for as a cat litter deodorizer. I have a cat litter box that is completely covered by an enclosure, which had a tiny carbon filter pad at the top, and an entrance for the cat at the bottom. Needless to say, that didn't work at all. I built something like this, with an intake at the bottom and output at the top. I used a 2 layer design, one of Zeolite (for the excessive ammonia, it can be recharged), and one layer of activated carbon. Powered it just like the one here. I must say, it actually works TOO well, since I used to judge by smell when the litter needed changing, now it hardly ever smells until it is REALLY overcrowded in there, sorry kitties!

[ci857s7]

Hmm. Placing intake at the bottom, as you did, would be a more efficient design than the one described above?

[gggonzalez]

It might be more efficient, since it is generally agreed that for a fan or pump, it is more efficient to blow, than to suck.

[Hatty]

Actually, it is more effective to suck for this filter. Thats why they always tell you to suck the hot air out of your home than is is to blow the cool air into it. I'm also part of a team who made a 5.5Ah, 115 volt battery pack of Li-polymer batteries. Our cooling method consists of two fans sucking the warm air out of the pack instead of pushing cool air in.

[ci857s7]

I was referring to the carbon filter. Unless the fan is powerful enough (or even if it is powerful enough), the intake of air through the box-shaped filter would be uneven? I'd imagine carbon closer to the fan will collect more particles than the carbon located in the bottom of the box. In that case filter that is located inside the cylinder with fan running on the top or bottom to draw/blow the air would have even filtration throughout the carbon.

[gggonzalez]

At these low flow rates, the actual difference between a push and a pull configuartion is probably negligable. Alot depends on the configuration of the filtration system. In the case of this Instructable, pull is preferred, since you can use one fan to pull air through 4 filters. I used a push configuration in my cat filter, primarily to make it quieter.

[SpencerW]

Quieter? So the filters in front of the fan were muffling the fan's whirring noise? I presume you mounted the fan on rubber/soft grommets to minimize vibration from being transmitted to the frame/box?

[Hatty]

The main purpose of the fan is to create a low pressure in the chamber of the filter. This low pressure is what forces the air through the carbon. Now, the pressure may not be perfectly uniform, but since this isn't being used in state of the art systems, I can assume it is. At this scale, the density of the carbon (how tightly packed they are in the filter) would effect the airflow more than pressure differences.

[sazure]

Better to clean the box even if it is a few times a day - as I do. (I have the same type) Easy peasy. I have a small container with bags nearby and another with the scope (with a liner). I change it whenever it is used (after it clumps) And the clumping clay can clog their air passages so I really did research to find one with ultra-low dust (the fan might help to pull that out however?

It is like you not being able to flush the toilet all day or until someone else does!!! YUCK! Cats like to be clean but more importantly, they can then track this material about your house.

Animal fecal material can kill a person if it gets into your blood stream. It may not smell to you but it is really nasty for them.

[SpencerW]

How does carbon work for filtering fireplace smoke from prick neighbors that don't understand anything about air quality? Will the carbon make my neighbors smarter so they don't choose to pollute both my air and theirs? That would be great carbon!
And how does activated carbon pellets like used here compare to sheets of carbon used as prefilters for HEPA filters?

[!Andrew_Modder!]

cant you make carbon??? i saw in a science book you add something to sulfic acid and carbon is made :-\?

[mvondran]

This is a link that gives you a more detail presentation on making activated charcoal.
https://www.wikihow.com/Make-Activated-Charcoal
There are thousands of others that can be found with a quick Google search. Good luck and be safe.

[ci857s7]

I dont think you can make carbon, unless you do some nuclear fission or fusion of lighter or heavier atomic nuclei. Carbon is an element.

[Bruce JohnS]

Of course you can !! Burn some wood !! And then you do this :

https://www.buyactivatedcharcoal.com/how_to_make_a...

And repeat you chemistry class :) It's just a friendly advise...

[!Andrew_Modder!]

oh i remember, if you put sugar into a thing of sulfuric acid, you can make carbon! thats all :-)

[Shadowfury]

Or you could just burn some wood...

[amddude]

lol

[circuitbreaker]

You can activate normal carbon, I have done it. You just heat it. you can also reactivate spent activated carbon the same way, it drives off the impurities it has collected.

[Redgerr]

that was qutie funny

[Win7Maniac]

Actually, the carbon is already there; the chemical reaction just separates it and takes it out of the sugar. However, you'd end up with a big, black blob of metal. . . Not much you can or would want to do with that.