Introduction: Activated Carbon Air Filter

Picture of 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

Picture of Needed Materials and Basic Idea

Computer fan
Activated Carbon
Window screen
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

Picture of 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

Picture of 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

Picture of 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.


!Andrew_Modder! (author)2007-08-17

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

ci857s7 (author)!Andrew_Modder!2008-03-27

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 (author)ci857s72018-01-12

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

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

!Andrew_Modder! (author)ci857s72008-03-27

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

Or you could just burn some wood...

amddude (author)Shadowfury2009-06-13


circuitbreaker (author)amddude2010-01-17

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 (author)Shadowfury2009-07-20

that was qutie funny

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.

G andK (author)!Andrew_Modder!2016-09-29

charcoal is a fairly concentrated form of carbon, activated charcoal is the filter media... and yes you cam make it. can make carbon ash (charcoal) by burning wood, but in this case you need activated charcoal.

Pierre-emmanuD (author)2017-05-11

What are the outside measuremnets of the box?

HowieG3 (author)2017-02-09

This looks great! How long does it usually last before the carbon needs to be replaced?

EmmaD68 (author)2016-11-19

Do you have to change the activated carbon regularly?

GurmeetS10 (author)2016-11-06

Please share results

DebiprasannaB (author)2016-10-17

how much it will cost

csatchell (author)2009-06-29

This device is exactly what I am looking for, but one question: How do you attach the 12 volt AC/DC converter to the fan wires?

Hatty (author)csatchell2009-06-30

There is just a positive and negative wire coming out of the fan and I hook that up to the positive and negative output of the power supply. Its as simple at that.

killprogram (author)Hatty2010-09-24

ah yes but be careful when doing so i would recomend getting all of your connections together and semi-permanently fastened BEFORE even plugging it in and i mean i know it is dc but what if the transformer where to break just then? ill tell you what you would have a positivie and a negative end of AC power going from one hand through your chest and heart, to the other

Hatty (author)killprogram2010-09-24

12 volts isn't really enough to break the skin and get into the body, so there really isn't much danger. But anytime you work with electricity you need to take precautions.

Wally_Z (author)Hatty2011-02-01

Well, you won't feel 12V. But if the amperage is high enough, it'll kill you if you let it arc across your heart.

Crapxxas19 (author)Wally_Z2011-02-08

12v cant arc across your body. The resistance of skin is too much. In any normal case, when working with 12v and under it is impossible to shock yourself unless you soak yourself in water for a few days.

Wally_Z (author)Crapxxas192011-02-10

If you actually READ what I wrote you will realize that I said "If the AMPERAGE is high enough, it'll kill you if you let it arc across your heart". Bad read^. AMPERAGE IS THE KEY WORD HERE. Google it if you don't know what that means.

G andK (author)Wally_Z2016-09-29

Ohm's law will tell you that the amperage flowing through you from skin contact is limited by the resistance of your skin. It doesn't matter how much amperage is available, at 12v with a typical skin resistance of 100k ohm you have a current limit of .00012 amps. It takes at least .01 amps to kill you. So you need at least 120 volts to kill a human through typical skin contact. And the current has to be sustained for some time to do the job, many people get electrocuted by 120v across the heart without dying, but it is because the exposure was short. As the voltage goes up, your ability to pull away from contact goes down AND the potential lethal danger goes up. 120v gives you a good jolt, but 400v tends to just kill right away.... but not always.

HOWEVER, if you break the skin on both sides of the circuit, resistance falls to 500 to 1000 ohms. But you have to beak the skin /twice/, on opposite sides of the heart. If you break the skin on only one contact, you still have a 50k ohm resistance to deal with.

This is why people don't die when installing car batteries, where you might have 600 to 1000 amps or more of 13.8vDC available, and plenty of scraped knuckles (broken skin).

But I have heard of someone killing themselves with a ohm meter powered by a 9v battery because they tested the resistance of their body using very sharp probes that pierced the skin. I don't know if that story was true, but at 900 ohms, a 9v battery can produce the deadly .01 amps.

You are right that it's not the volts, but the amps that kill you, but ohm's law predicts you are unlikely to ever see lethal amps from 12v. Breaking the skin not once but twice on both hands is required to make 12v dangerous. But even the smallest 12v power source I can think of can do .01 amp.

An old electrician's trick, work with one hand in your pocket when touching a live circuit with a tool (any tool, even insulated tools designed for this), and wear clothes and shoes to provide enough resistance for whatever voltage you are working near. Better electricians use gloves that they test frequently.

Crapxxas19 (author)Wally_Z2011-02-10

You need voltage for amperage to kill!!!
I have put my fingers across a 12v 5a source and i didnt feel anything. You need at least 40 volts with moist skin to even feel anything.

Crapxxas19 (author)Crapxxas192011-02-11

Think of electricity like water. If you put your finger at the end of the faucet no water flows. This is like low voltage (pressure of water is low) and no amperage (there is no water coming out.) If you are using a hose, there is some water leakage because the pressure is higher so it means that amps are flowing. Basically you need some voltage to make amperage effective enough to kill.

GsE-Lance (author)Crapxxas192011-03-10

30mA kills a person at 230v,
Ampere = Volts/Resistance, in this case 12v / 1000r (resistance of the skin)
Therefore Wally_Z's arguments are invalid.

jonnybegood (author)GsE-Lance2011-12-10

Yeah yuo are rigth! V=R*I (V=Voltage in volts , R=resistance in omhs and I is current in amperes),WELL this is the OHM Law,and on the other side any DIELECTRIC have a constant, a point that change from not conductor to a conductor(For example the dialectric constant of the air is about 3 Kilovots(3000 vols) taht explain the spectaculr pictures of tesla or the ligting)..

Crapxxas19 (author)GsE-Lance2011-03-11

THANK YOU!!!!!!!!!!!!!!!!!!!!!!!!!!
Some people need to know what they are talking about, SERIOUSLY!!!!

Crapxxas19 (author)csatchell2011-02-08

cut the wire open and solder the + to the red and _ to the black. If you cant tell which is + and - guess and if the fan doesnt work, switch the wires.

DemoportS (author)2016-07-08

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DemoportS (author)2016-06-22

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BretW2 (author)2015-08-31

Here's a link to a website where you can purchase activated carbon filter products.

BretW2 (author)2015-08-23

Absolutely brilliant! Great job covering the steps and including photos. Thanks for posting this. Would you mind if I post a link to this on a blog?

hazimmzaidi (author)2015-04-30

did you make this product as a filter for vehicles?

Michael_Bell (author)2012-06-03

Great Idea, One idea though:

You can buy these dryer sheets that are designed to give you clothes a nice smell, you should buy a box of them and tape them to the window screen.

Hatty (author)Michael_Bell2015-03-29

Activated carbon physically captures pollutants. Dryer sheets just mask odors.

Angeeeeeeelika (author)2013-11-05

Hi. Is it possible to use activated carbon as car smoke filters?

Hatty (author)Angeeeeeeelika2015-03-29


undrline (author)2014-02-19

I like this. Looks like I could make a less precise version out of anything, even popsicle sticks. I'm curious about the air flow, though. Especially after the carbon has settled, how hard is that fan working? I ask because I'd want to reverse the direction of the flow and make it flatter rather than cubed. Like you said, forced air is more difficult. Also, how often would the carbon need to be refreshed?

Hatty (author)undrline2015-03-29

The fan doesn't work very hard due to the large surface area of carbon. This allows the air to move slowly through the carbon which reduces the load on the fan. Making the filter flat is possible as long as you maximize the surface area of the carbon.

I replace the carbon about once per year.

beatbox.sir (author)2014-09-22

this is nice... and i could use it as a base research for my papers... thanks... but could a fan run in a 5 volts ac??

Hatty (author)beatbox.sir2015-03-29

All computer fans use DC and most 12 volts. If you want to use AC power, you need an AC fan.

drmzsz7 (author)2015-03-25

Would this work for scrubbing ammonia gases from pet litter?

Hatty (author)drmzsz72015-03-29

Yes. It will reduce the smell from a litter box.

thanhoattinh (author)2014-01-22

Activated coconut carbon, Bentre provine, Vietnam

bettablue (author)2011-12-22

i have found something better than aquarium carbon.

you can buy surgical masks that have a type of active carbon material layered between two needle punched non-woven fabric they are great.

the needle punched fabric filters out dust
and the active carbon material can filter out bad smells
the surgical mask can also filter out viruses and bacteria so it works like a hepa filter! all you have to do is cut of the ear loops and the sides so the pleats open up then you can use it. it costs like £3.00 for 50 masks so it is so cheap and they last for about 1 month.

WERNER SLABBERT (author)2010-06-10

you might actually try three fans in line. say for argument's sake the first fan gives you one bar of pressure, a second in line would double that to about 2.3 bar of pressure and a third would then daouble that to about 4.6 bar. in theory that is.

gilbert2048 (author)2008-08-23

this could be good for a solder venting system

Hatty (author)gilbert20482008-12-31

It actually does work as a solder venting system. The only problem is that it doesn't suck in air at a high enough velocity to make it effective. Even though it does suck solder fumes in and filter them very well, most of the fumes just go straight to my nose. If I wanted to make one, I would probably only have one side of carbon, use a converging nozzle into the fan, and only use a .25" thick wall of carbon. This would allow for a much greater airflow and, hopefully, pull the fumes away from my face. But, since I don't solder much, I think I can do without it.

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