Would someone please critique my CO2 scrubber/air filter?

[sofa king]

Hi all,

So I was all proud of the fact that we kept my girlfriend's pipes from bursting this frigid weekend, despite the fact that we have no heat except for a few electric space heaters. I did it by putting plastic up over every window, and ruthlessly hunting down every draft and ill-fitting door. Hello, balmy high-40s--only ten or so degrees below ground mean temperature!

Everything was great until I realized that my girl smokes like a pack a day. After this weekend, the air was blue and it gave me a cough and a sore throat. Then, her house-mate came home with a new little propane heater, which further concerns me because it will be competing for oxygen with the people and the cigarettes (it does, however, have an oxygen depletion sensor, which will come in handy).

A limited amount of research took me to activated charcoal filters, which in addition to being able to trap absurd amounts of airborne particulates, can also act as a reasonably good carbon dioxide scrubber. Apparently, the charcoal will store CO2 as long as the CO2 content of the air is higher than that trapped within the filter, and it releases it if there's more CO2 in the filters than the air, so I think I can move my filter system outside and run it for a while to "discharge" it.

I have two floor fans, some cardboard boxes, about 50 yards of duct tape, and not a damned dime to spend on charcoal filters. However, I see that they're often used with microwave ovens and in kitchens, so I think I might be able to acquire a few used ones.

Here's my design, should I find some filters:



So I have a lot of questions.

1) Activated charcoal can apparently ignite and release carbon monoxide if it comes into contact with ozone (O3), that stinky metallic stuff you often smell when electronics (such as two floor fans) are overloaded. Can that happen with the trace amounts of ozone normally released in the home?

2) Activated charcoal seems to do a nifty job on carbon dioxide, but what about carbon monoxide, which is also being produced by my girlfriend's cigarettes, candles, and other stuff?

3) Using fans in a push-pull configuration has never worked very well for me in the past. Should I maybe consider using just one fan, and if I do, do I use it to push the bad air through the filters or pull good air from the other end?

4) How well can I expect dirty filters to work? Can I clean them in addition to discharging them outdoors? Is this going to work at all?

5) Where is a good place to find discarded charcoal filters? Restaurants come to mind, as well as trash day in the neighborhood. Other than that, I don't know.

6) Am I crazy? Am I going to kill someone? Is my infernal machine going to turn dogs into cats or make my willie soft?

As I mentioned before, there will be no throwing of money at this problem. There is no money, and there won't be for the rest of my life, so just forget whatever Brookstone or the Sharper Image offers, besides design plans. I doubt my better half will quit smoking. This system is designed (or thrown together) with the intent of working in addition to the house being regularly aired out. And yes, we do plan to get a lot of plants, too.

Thanks so much for your input.

[dhpgetsit]

1. You need to vent your heater.

An unvented propane heater will emit CO2 and H2O. H2O will condense an cold surfaces and cause water problems. CO2 while not toxic will replace your oxygen. You may also get a build-up of CO (Carbon Monoxide) which will kill you much more quickly than your girlfriend's smoking.

As for capturing the CO2, I think trees are the best.

[sofa king]

2. Yes, the propane heater concerns me.

That's actually why I decided I need to do something right away. I'm not so worried about the water condensation, as the humidity is almost nil and we have no condensation issues when boiling water. (I'm placing stock pots of boiling water in front of the fan-heater as a way to transfer a few hundred BTUs of heat from the kitchen to the bedroom, as well as to humidify) The CO buildup worries me a lot, and that's why I'd like to know if charcoal filters can catch it.

The propane heater, which is tiny, requires eight square inches of input and eight inches square of ventilation. Since we have ancient hardwood floors over an uninsulated basement and I can see when the basement lights are on through the cracks in the floor, ventilation from below isn't a problem. It also runs through a bottle of propane faster than it takes the owner to go out and buy another one, so I suspect its novelty will wear off fast. If it doesn't, and we all start having flu symptoms, I'm just going to demand it be shut down.

The device itself is actually the best warning we have for oxygen depletion, as it will shut down and sound an alarm if air begins to fall below breathable oxygen ratios. Maybe we need a canary, too.

[dhpgetsit]

3. Even though it is dry in the house

The main byproducts of burning propane are CO2 and water vapor. Each molecule of propane burned creates a molecule of water, if I recall correctly.

[sofa king]

4. More than that.

C3H8 + 5(02) = 3(CO2) + 4(H20)

[NNadir]

5. Activated charcoal will do very little against carbon dioxide.

To the extent it works at all on carbon dioxide it would be quickly overwhelmed since it works by surface area.

Air blowing over carbon could actually be bad for you, since it is likely to raise carbon particulates in the air. Particulates from diesel engines, automotive engines, fireplaces and similar combustion devices are a serious issue in air pollution and are responsible for millions of deaths each decade.

A better solution for carbon monoxide would be ideally to actually run air over a catalytic converter of the type used for automobiles. This will oxidize carbon monoxide to the dioxide, which is present in every breath you take. (It is not a serious toxicological issue except at concentrations well above ambient atmospheric levels.) It will also destroy any nitrogen oxides present in the air from exhaust and other pollution sources, like power plants.

Catalytic converters also catalyze what is known as the boudouard reaction which is C + CO₂ <-> 2CO. This is followed by another oxidation in the presence of air CO + O₂ <-> CO₂.

The net reaction, with equilibrium far to the right, is C + O₂ <-> CO₂.

There are cheaper commercial air filters that use HEPA filters that are good at removing particulates.

Catalytic converters, which contain platinum and palladium and a few other precious metals coated on finely reticulated surfaces like aluminum oxide, are the best at removing toxic gases and would be the best at removing the most serious risk of an indoor carbon monoxide risk from a propane heater. However they also catalyze the oxidation of propane (and methane) by air, meaning that in the event of a gas leak, they would potentially catalyze an explosion.

I have worked with platinum and palladium catalysts supported on carbon or in organic solvents and they do occassionally spontaneously ignite when exposed to air, usually just sparking. I had one very small explosion in a metal vessel while pouring an unwetted catalyst into a vessel, a "poof" kind of thing, but in a room full of gas and air well...

Probably with any kind of indoor heater of this type, a carbon monoxide detector, available at most hardware stores or available on the internet are advisable. If the alarm goes off, you can shut off the heat and go outdoors to get oxygen. (In very bad cases, people are sometimes placed in hyperbaric chambers with oxygen at high pressures, if available.)

Indoor gas heaters have resulted in carbon monoxide deaths. The symptoms of carbon monoxide poisoning are lethargy, headache, and a feeling of weakness.

I hope this helps. Good luck.

[sofa king]

6. Thanks for your reply.

If I could find some HEPA filters I'd be really pleased, but I think they're less easy to find in my price range, which is zero.

A carbon monoxide detector is also off the table, unfortunately. I'm going to have to bank on the fact that while I've reduced outside airflow into the rooms by a major percentage, I have not and will likely never be able to completely interrupt it. Sixteen square inches of induction and ventilation really isn't very much.

[TxRider]

7. Yup your crazy

A panel filter isn't going to do anything at all really, well maybe for a short time.

To get anything really accomplished you would need a large amount of activated carbon, like a 50lb bag. Dunno what it would do for removing CO2 though, likely not much.

Like the pot growers use to keep the pot smell out of their exhaust from the indoor greenhouses, or in a smaller version what this guy made....

http://www.instructables.com/id/Activated-Carbon-Air-Filter/

He used granulated carbon from a pet store for fish filters, probably cheaper to to go buy it from a water treatment dealer.

It'll help loads with smoke and it's odor but you still have the issue of the heater consuming all you oxygen and replacing it with deadly gasses.

[wtmusic]

9. Crazy for asking an honest question?

:eyes:

[TxRider]

11. Umm, he asked, "Am I crazy?"

Just answering the honest question.

[sofa king]

12. Hey, I really like that.

I considered using my computer, too, because I have a liquid-cooled case with a nice fan stack on top. I think all I'd need to do is interpose a filter between the radiator and the exhaust fans (it "breathes" from bottom to top). At full power, folding proteins, it might generate four or five hundred watts of heat, too.

But that would lower the efficiency of the system, which would raise the heat in the case, which means I can't overclock the computer as high as I currently do, which means fewer people get fragged in Team Fortress 2. ("jackabramoff" is my usual screen name)

However, now that I think of it, I already use one of the floor fans to cool the computer. If I build the two-fan box setup, I can simply place the whole system right next to the computer and the rig still gets a 50 cfm breeze, and the filtered air gets slightly heated as it leaves the computer.

Hmm. Maybe I am crazy. Anyway, thanks for the tips!

[OKIsItJustMe]

8. “Soda lime” is more what you’re looking for…

http://en.wikipedia.org/wiki/Soda_lime

[sofa king]

13. Yes, I looked at lime, too.

I discounted it at first because I've had bad experience with sodium and calcium reactions. They can be highly exothermic, even explosive, and if I recall correctly they tend to spit out a high proportion of isomers, radicals, and other unpredictable critters which I can't predict or deal with.

But if I could find an actual soda lime rebreather device, I'd definitely be in business.

[OKIsItJustMe]

15. This research may interest you…

http://archive.rubicon-foundation.org/4992

[CHIMO]

10. You

Will not survive.

CO will kill all of you.

Once it is in your system you will need something like a decompression chamber. You will not realize it.

If it is your property you will loose lots of money from the mold that you will produce in the house.

Don't have to worry about the CO2. You have to be afraid of the CO.

If you don't know what is going to happen, then Don't do it!

If you know what is going to happen then you are a murderer. Simple.

[sofa king]

14. Well, there's the worst case, I guess.

I should have added at the beginning that I have no control over the behavior of the people in this house. They're not going to quit smoking and they're not going to quit trying to heat the house any way they can. Hell, the guy upstairs is trying to heat his apartment with his kitchen range, so there's a good chance we're going to be immolated before I finish this project, anyway.

So I prefer to think of the situation as me trying to prevent my own murder, and their own suicide, through their bad habits.