A carbon air filter that works?

November 4, 2009 3:36 AM

Have you ever encountered an activated carbon air filter that actually removed odors, leaving the output air clean? Which one?

Never in my life have I been so peeved at the whole steaming pile known as consumerism.

I've tried no less than 7 times now to find something that works.

I bought a honeywell filter appliance, a febreze, and a bionaire, only to find that there was something wrong with the carbon filter material itself in all 3 cases. Not only does it not clean the air, but even after more that a week running in the garage (12 days in the case of the honeywell) it was still releasing some sort of awful fumes. I strongly suspect the smell is added intentionally by companies to make the air "smell clean" to ignorant consumers.

After the misfortunes of finding the honeywell and febreze machines didn't work, and having bought and not yet gotten around to returning the bionaire, I decided to try something.

I bought some carbon filter stuff (they call it " paper" but it more like a mat of hair made from Polyethelene terephthalate), the sort they use in air conditioners in office buildings, from Camfil Farr. To remove odors, suposedly. Then I took the filter out of the bionaire machine and taped a few square ft. of filter paper over the intake.

Exactly the same smell and problem after running it for a week. I figured it was just a matter of finding a brand of carbon filter that actually worked. I tried 3 more filter medias from various sources, all with the same problem.

I read up on some of the physics and design principles and it is clear that it is easy to make a functional filter that will absorb household smells, but
apparently it has come to the point now that companies have decided to stick with just duping the masses into accepting useless junk instead, no matter how little effort making a functional product actually requires.

So has anyone ever encountered a filter that works?

BTW this really matters because I live in a house with no provisions whatsoever for bringing in fresh air during the winter.

posted by Nish ton to shopping (11 comments total)

It sounds as if your expectations may be unrealistic. Could it be that whatever is producing the problematic odor is doing so faster than the filter can remove it? What odor(s) are you trying to address?
posted by jon1270 at 4:12 AM on November 4

I have built my own activated carbon filtration system for a laser cutting machine that produces noxious smoke and poisonous fumes. If the humidity is high in the space you are trying to filter, you can saturate the filter in a matter of hours, much less days.

Filtration may not be the answer for you. Try to eliminate or reduce the smells at their source.
posted by fake at 4:16 AM on November 4 [1 favorite has favorites]

I live in a house with no provisions whatsoever for bringing in fresh air during the winter

No mechanical filter will provide you with oxygen. Try houseplants.
posted by flabdablet at 4:21 AM on November 4

Seconding fake: activated carbon does work, but is used up very quickly. To the point that the "activated carbon" in household air filters is pretty much a novelty unless you replace it every few days.

Also, carbon doesn't adsorb everything, and is entirely useless against some types of odors. Not sure what odors you're dealing with here.

As for the "some sort of awful fumes", I'm not sure what you mean. Most air purifiers don't release anything, and carbon certainly doesn't. The one thing they might release is ozone if it includes an ioniser, which I would definitely describe as "noxious fumes". Ionizers are nasty and cause many more problems than they solve. Turn that feature off if your air filter includes it.

Your best bet is a large-volume HEPA filter. The bigger and noisier the better, and replace the HEPA filter regularly. Don't bother with the carbon filter unless you're going to replace it every week or two.

Replace your furnace's filter every month or two or else it will work against whatever air filters you have.

I read up on some of the physics and design principles and it is clear that it is easy to make a functional filter that will absorb household smells, but apparently it has come to the point now that companies have decided to stick with just duping the masses into accepting useless junk instead, no matter how little effort making a functional product actually requires.

If it's easy, build one - you'll make a million dollars. I'll invest in your company.

In my experience there's nothing easy about it. There are a thousand different "household smells" with different attributes, and no easy way to remove most of them at all. Brute-force filtering (i.e. HEPA) will remove dust and other particulates but won't help with some organic smells (i.e. pet urine), some kinds of smoke, and some fumes -- and by the time you install enough HEPA filters to reliably filter the whole house you won't be able to hear yourself think.

Houseplants might help, and air fresheners might help mask odors. If you can get even a tiny bit of fresh air, it will make a huge difference. Good luck.
posted by mmoncur at 4:38 AM on November 4

By the way, the Honeywell HEPA filters (the big round ones) are the best I've found. Expect to pay $100 to $200 for a good one. If it doesn't work, you may need to lower your expectations...


The big question: what "household smells" are you dealing with? Even with the tiny amount of ventilation and fresh air you get from a furnace and a poorly-insulated door or two, the average home shouldn't have much of a smell at all. If you have something that makes smells (i.e. a litter box, a garbage can, cigarettes, ?) dealing with the source directly will work far better than filtering.
posted by mmoncur at 4:47 AM on November 4

I can attest that the Can brand of filter works for more industrial applications. Perhaps you need something bigger than what is marketed for use in a home?
posted by iurodivii at 8:05 AM on November 4

Check out the Austin Air Healthmate line of filters. The filter is multi-staged and contains 15 pounds of activated carbon. We have one and it works!
posted by tman99 at 8:23 AM on November 4

I bought two big HEPA units, which were ineffective. Sprays (Febreeze), evaporative stuff (Air-Wick, plug-ins) and scented sprays work by numbing your sense of smell and are otherwise useless. Negative ion generators are pure quackery, and they produce ozone, which tears up your throat and lungs.

The only thing that works is ventilation. Blow outdoor air through and let the room heat up again. You can heat the outside air before blowing it through, but the cost of electricity is greater than letting the furnace do the work.
posted by KRS at 9:16 AM on November 4

Proper activated charcoal looks exactly like it sounds . Granules of carbon in a blocky box with a mesh holding them in place. You can buy industrial filters like this and simply attach box fans to one side, eliminating the middleman role played by the air cleaning device. You want to control the airflow so that your fumes go directly into the fans. If you're hoping to recirculate all of the air in the room, to eventually capture the diffused fumes, you'll saturate the filter too soon with minimal effect.

Use incense sticks to track the air directly from the source to the filters, using other small fans if needed to steer it there. Usually the filter should not be on the floor, but mounted near and above the source of fumes.
posted by StickyCarpet at 9:25 AM on November 4

Hm, fresh air is pretty hard to get, because this is a new house (so well sealed) and the other people in the house won't let me turn the main furnace fan on (and apparently have no sense of smell.) Also they are not intelligent enough to see the logic behind opening a window (just a crack) in winter.

I know they use activated carbon to freshen air in office buildings... And the physics are very much there if you want to adsorb household smells like food and, well, people smell (large molecules.) which is what I want to do. I'll keep searching for a suitable filter media I think.

Yes stickycarpet, that's all very well in theory, but actually getting a hold of that stuff is not as easy as it sounds.

I looked into those austin air things, but they're a couple thousand buck each. There's got to be a better way - all it comes down to is enough filter media and a fan after all.
posted by Nish ton at 4:11 AM on November 5

the other people in the house won't let me turn the main furnace fan on (and apparently have no sense of smell.) Also they are not intelligent enough to see the logic behind opening a window (just a crack) in winter

Sounds to me like your problem is primarily political, not technical, and that houseplants will in fact work better than a big box with a passive-aggressively noisy fan in it. Use big plant pots to maximize the surface area where room air and topsoil come in contact. Put loads of them in your own room.

The best place to put a charcoal filter would be in a range hood over the stove.

The best way to deal with stinky fellow humans is to take the lead with the vacuum cleaner and the washing machine.
posted by flabdablet at 11:30 PM on November 5