DIY Different types of carbon.. Pros and cons?

greenjeans · Feb 24, 2015

So I have decided to make 2 DIY carbon filters for my box. The fact is that I just don't have $150-$200 to spend on a good can fan and a phresh filter. I have looked at just about every thread and design on the internet about DIY filters, and it seems like those who are good DIYers, and those who put a lot of thought into it, have been satisfied, overall, with their DIY filters. I saw some ridiculous designs, and some good designs, but in the end, I have decided to go with my own design.

I am debating about exactly what kind of carbon I should buy..

I will be making two of them to make sure I have plenty of airflow in the box.

They will both be identical, and will use some small square buckets that I have around the house, screen that I also have on hand, and two honeywell turboforce fans. My only expense should be carbon and a second fan.

The turboforce fans are rated at 350cfm. When mine is tightened up in the hole at the top of the cab, it definitely creates some serious negative pressure, or at least it did before I increased the size of my passive intake. So I think it definitely has enough juice to pull through an inch and a half of carbon. With two running through carbon, I think I should have even more airflow than I have now with a single unrestricted fan.

If the design works out well, I will create a thread to share my design with everyone.

If anyone is familiar with the logistics of filters and carbon, I DO wonder what is more effective... Granular or pellets, and also coconut shell carbon vs other types. Has anyone watching this tried both and have some data based on that experience for me?

Here are some pics of my box, which is 3x2@4feet tall.

steelrat · Feb 24, 2015

I can't advise you on the DIY aspect, but i bought a filter for £15 ($23) and it lasted 3 years.

I also got a cheap extractor fan (fantronix) for about double the price of the filter.

All the best,

steely

guerilla · Feb 24, 2015

A question id like answered myself. I use activated charcoal for aquariums mixed with ground coffee pulled through a choir pot.

sniper · Feb 24, 2015

Son of Hobbes said:
Take all this with a grain of salt because I'm still compiling notes on everything (already have a few pages!) but this is a bit of what I've drummed up so far.

The 412 in the "RC 412" is referring to the mesh sizing distribution of the carbon. The carbon is run through two screens (or sieves,) trapping only the desired range of particle sizes. The 412 is actually 4 mesh x 12 mesh, which means it will have particles smaller than 4 mesh (4760 microns) but larger than 12 mesh (1680 microns.)

Think of it like this:

X = range of particle size of the carbon used
In 4 x 12 mesh,
X < (is less than) 4760 microns in particle size
X > (is greater than) 1680 microns in particle size

So there should be a range of carbon particle sizes of 1680-4760 in RC 412 activated carbon.

The other common mesh size is RC 48, which you'll see on other carbon scrubbers (big name brand ones too!) That's 4 mesh (4760 microns) and 8 mesh (2380 microns,) so there again should be a range of 2380-4760 in the RC 48.

The thing that probably is going to be much more important though is what type of activated carbon the manufacturer is using. It looks like there are 3 different types of activated carbon commonly used:

mineral (coal)

coconut fibers

wood based (peat)

Activated carbon from coconut fibers is supposed to have more/larger surface area than coal-based carbon, but it has a higher ash content than coal based (which I've found conflicting information on how much ash content reduces efficiency.) The other major thing I read about coconut based carbon is that 85-90% of the surface area is micro-pores, which is not necessarily the only thing you want when trying to filter out a wide range of VOC's produced by your flowering cannabis.

Micro-pores < 1 nm in size
Meso-pores 1-25 nm in size
Macro-pores > 25 nm in size

Macro pores are essentially access points to micro pore. If your surface area is primarily micro pores, you have no access point for larger VOC particle sizes to essentially get trapped into through adsorption.

Wood based carbon is supposed to be mostly meso and macro pores.

Coal based carbon is the best mix of all micro/meso/macro pores (which is probably why it's one of the "best touted" choice of most carbon scrubber vendors.)

About the ash content, some of the information I've read (and I see a lot of vendors use it in their ads) is that the ash content (which is usually a percentage, like 13% ash content in RC 412 carbon,) is directly related to the efficiency of the carbon over-all. So 13% ash content would make the carbon used no more than 87% effective (period.) Another reason why it seems like that would be a good reason to use coal based carbon vs coconut in terms of efficiency (most coconut based carbons average around 20% ash, or 80% efficiency.) BUT, then you have the "eco" side of it (if that floats your banana boat,) where you're basically firing coal vs coconuts (which are probably arguably much more renewable.) Then I read some other reports that the natural (emphasis on natural) ash content produced in the process doesn't effect the efficiency; only if it's ash produced by a re-firing or regeneration process (which would make it non-virgin then, I'm pretty sure.) So not quite sure what is what there; can see how claiming ash is much more important than it atually is could be a marketing trick too.

Then there are things like appropriate amount of contact time; temperatures and humidity (high humidity renders scrubbers less effective, high heat generally releases more terpenoids (volatile compounds, etc etc.)

So I'm not totally sure how much of a difference RC 412 vs RC 48 really is if the source material is both coal based carbon of the same quality/grade. My first thought that is that the wider range of micron size could be a blessing or curse as that could potentially filter out more of OTHER things in the air as well, diminishing the life of the scrubber. On the flip side, by going with the smaller range, you could be missing out on a range of particle sizes that could stink. I mean, look how many terpenes/terpenoids cannabis produces. Stiiiiiinky. In either case; it's a good idea to keep the air quality of the tent and surrounding area as clean as possible so the filter is working more on filtering cannabis smells and less on your dirty gym socks, cigarettes smoke, cannabis smoke, etc etc.

Anyways, like I said, this is just part of my note-taking for the night; have some data checking to do.

But, that's some work for another day, class :Hookah:

Here's some carbon info

greenjeans · Feb 24, 2015

So, sniper, is your take on that info that coal-based carbon is the best option? Thanks for the info, btw!

sniper · Feb 24, 2015

That's what's in my ventech filter and it's 2 years old and still working

greenjeans · Feb 24, 2015

That is really helpful. I appreciate it!

Panic · Feb 24, 2015

I am kinda in this same boat, just got a 600w cooltube in a 3x2.5x8 closet so its going to need significant air movement. Can't decide on the filters There are even some chinese companies that i am sure are being re-sold as some knock off brand. They also have that chinese carbon made from coal as which here are the stats from that company and just found the iodine absorbtion for rc48 on tons of random sites (they vary slightly)

Carbon Rating: RC-48 – Iodine Absorption: 950mg/g
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