Activated Carbon Air Filter

This instructable shows you how to make an air purifier to filter pollutants such as tobacco smoke, pollen, 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.

Comments

[Michael_Bell]

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.

[bettablue]

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.

[csatchell]

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?

[Crapxxas19]

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.

[Hatty]

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]

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]

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]

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]

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]

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.

[Crapxxas19]

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]

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]

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]

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)...so taht explain the spectaculr pictures of tesla or the ligting)..

[Crapxxas19]

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

[WERNER SLABBERT]

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.

[XOIIO]

Can you cut charcoal filters, or does all the charcoal stuff come out?

[MrHyde]

for more pressure maybe use this http://www.instructables.com/id/Tesla-turbine-from-old-hard-drives-and-minimal-too/

[chamunks]

I'm curious how you would use this turbine to create pressure or apply the turbine to this.  Maybe I'm just browsing instructables too late at night. 

[lemonshark10]

By manually spinning the shaft of a tesla turbine th opposite effect is acheived and pressure is generated

[junits15]

an extremely more affective way of making an air purifier is to buy a negative ion generator u can get them heresimply put the part with the prongs on it into a continous screen that is wrapped around this. the negative ions attract any type of dirt in the air and cause it to stick to the screen. only downside is that the screen needs to be cleaned every now and then. the negatitave ion generator can also be use to charge a lyden jar! :D

[junits15]

fixed link
http://www.goldmine-elec-products.com/prodinfo.asp?number=G1783

[chamunks]

Broken Link.

[junits15]

damn i hate it when that happens!

[chamunks]

Thank you I definitely appreciate the link fix I will certainly try to incorporate this into something.

Do you think this generator could be used in an ion fan build of some kind.

[junits15]

im not sure if it would work as an ion fan, I've never personally played much with these things (I have a certain fear of high voltages) and I dont know how powerfull one would have to be to generate an ionic wind,  But I wish you good luck anyway!

[chamunks]

amperage is what you need to worry about as long as its not past .87 amps I believe its all good.

[junits15]

yes but its still dangerous, especialy if you have a heart problem.

[JusCoz]

A simple HEPA filter works great, and is a lot cheaper. It also lends a certain interchangability. Cool instructable tho.

[lemonie]

Activated carbon has an affinity for organics, such as the non-prticulate components of smoke. This is less a particulate filter and more an odour / volatile organics filter. I doubt the effectiveness with pollen, but surely both HEPA and carbon could be used. L

[chamunks]

Certainly could use a hepa filter in this equation could always put a hepa filter Just below the fan inside the box this would also help prevent you're fan from catching all the really tiny dust particles. 

But Ideally if someone was concerned about really purifying the air the DIY method, one would use three filters.  

Some reusable/washable filter  Than a Charcoal filter for smell and finally a hepa certified filter for biotic and allergenic issues.

The reusable/washable filter would catch big dust and hair that can significantly shorten the lifespan of you're Charcoal and Hepa filters. 

The Charcoal filter was covered in the comments and article so I wont bother but link you here. The carbon specifically used in this ible was from the looks of it classified as GAC Granular Activated Charcoal.

Finally the HEPA Certified Filter will get rid of airborn pathogens and the rest of the superfine dust.

[Hatty]

That is true. Activated carbon works on organic gases. The only reason I say it works on pollen is because every time my allergies start going crazy, I stick my face in front of the fan on the filter and my problems go away. There is probably another explanation for this, but it works, so I use it.

[Mitten]

Would activated carbon really do anything for the air? It would seem like there would be a lot of gaps around the carbon.

[monterto]

there are a lot of carbon filters out there. they are the most effective filters for the price. the activated carbon doesn't catch particles like a sive, it has a high surface area and a high absorption rate so as particles get sucked through the filter and brush passed the carbon they get sucked into the pores of the carbon. Brita water filters work the same way. this is why they need to be changed periodically also.

[PacoBell]

Actually, don't activated carbon filters operate on the principle of a_d_sorption rather than a_b_sorption? They rely on their high surface area and the material's surface energy. Wikipedia is your friend :)

[chamunks]

You can also aquire a wide range of activated charcoal size grains so from what looks like gravel (used in this ible) to almost a fine powder.  Of course you will have to choose your screens accordingly and airflow can become lessened the finer the powder you choose.

Airflow, Purity, Efficiency,
Its kind of a pick two scenario, you can have any of these two options but you sacrifice the third.

[!Andrew_Modder!]

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

[punkhead58]

Um...you can make carbon ash (charcoal) by burning wood, but in this case you need activated charcoal.

[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.

[!Andrew_Modder!]

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

[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.

[Shadowfury]

Or you could just burn some wood...

[Redgerr]

that was qutie funny

[amddude]

lol

[Geekmandude]

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.

[nckballer]

I also forgot to say attach your fan box to the mailing tube

[nckballer]

For adding another filter instead of using paper to construct a tube just use a 3"x36" Mailing tube you can find it at packaging stores(They are about $5) for this size but get the size you need keep in consideration that I just had the tube laying around, if I were to of bought it, it would be a lot shorter because I just dont need that much! Now back to what I was saying you can attach the tube to your carbon filter box right above the fan(attach it anyway you like glue,tape,whatever)make sure you dont have the tube too big and in the middle of the tube cut it in half this is where you will use some pantyhose and chicken wire to make your carbon filter and at the very take a little cardboard box(or make one) and cut a hole for the fan and mount it on the inside or outside of it and there you go you should now have decent enough pressure to get the air flowing. write me back and tell me what you think!

[gilbert2048]

this could be good for a solder venting system

[Win7Maniac]

Hey. . . GREAT IDEA!!! I've been wanting something like that for a long time, I can't believe I didn't think of that!

[Hatty]

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.

[Chowmix12]

Instead of 4 inlet vents try limiting it to 1 so that the air pressure is not 'diluted' and you will have greater suction towards four soldering station... And also, the fumes going to your face are harmless, after going through the filter...

[Andrew Heine]

increase venting CFMs (cubic feet per minute, flow rate) by making a grid of four fans to draw the air. or whatever amount is necessary. the air velocity through the filter should be 200 feet per minute, and big enough to catch all the fumes. quick calculation

[gilbert2048]

thank you for that, and yes i would use a funnel as well

[Andrew Heine]

try using fabric softener instead of the inside screen to combat the carbon smell.

[Redgerr]

that makes sence, i think you are right on O-o

[GEEK1]

Is there a substitute for the carbon

[Hatty]

There probably is something that does the same thing, but I don't know what it is. Whatever it is, I doubt it will be as inexpensive and easy to obtain as activated carbon is.

[GEEK1]

thks

[geeklord]

I got an idea!, use an old aquarium filter for added aeromatic effects!

[matbh]

too smart...

[ron2470]

nice idea

[Shadowfury]

Great idea. Will it spark?

[hg341]

well done ^{if only i had a use for it}

[runcyclexcski]

commercial air purifiers blow air at ~100+ CFM, and even at those speeds they can substantially improve the air quality in small bedrooms. THe computer fan's blowing speed can not provide the speeds necessary for making any noticeable difference in the air quality. Get a particle counter (or a VOC detector) and see for yourself. The idea of the cat litter box filter mentioned in the comments would would much better because it deals with a very small, contained area.

[Hatty]

Very good point. The computer fan I use doesn't really blow air a large quantity of air. But, based on my own experiments, it is very effective at cleaning a room. My neighbor smokes in her room a lot and with this thing running all day (all day is the key), it smells much better than it used to. Even people who didn't know about the filter thought so. But I would like to verify that with a particle counter. Where do you get those? I've wanted one for a very long time. On the topic of volumetric air flow, where could I get a better fan to improve this while remaining quiet. That's one of the things I like about the filter is that you cannot hear it. A couple in parallel would work, but one fan would be much better.

[sageserver]

if you need a quiet fan that blows lots of air. use a blower.(different from a fan) they dont have air speed but they have more cfm.

[Hatty]

I may be wrong, but based on my experience with blowers, they are much louder than the fan I have here. They are, however, much better at pushing air at a high pressure, something that would go well with this filter, since it is difficult for the air to travel through the carbon. I was actually going to use a blower with my filter, but didn't have one that I could salvage off an old computer. Most of the things I make have parts that I "acquire" for no cost. Because of this, I didn't want to buy a blower. Thanks for the comment though.

[Derin]

try automotive grade engine fans,it would be bigger and more effective,but the fan draws SOO MUCH air thru

[junits15]

it is realitavly simple. i noticed that there is an inner and an outer screen on your device the logical thing would be to put the negative ion generator on the inner screen to avoid getting killed. it is on the outside in the pic for visual pourposes

[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.

[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.