DIY Carbon Filters

I’d guess for people that live where cannabis is not legally accepted, the boastful smell that oozes from the cannabis plant is less of a joy than here in Colorado, where adults age 21 & up are legally (and without medical restriction!) able to cultivate up to 6 plants. While, in part, that was just bragging, the larger point remains: cultivating cannabis should be smelly.

Earlier this month, we gave up the deets on how to build your very own grow box. Contained within that nugget of cannabis cultivation knowledge, the term ‘carbon filter’ came up and it is the application of homemade carbon filters that allow so many at-home ganga growers to evade the olfactory arm of the prohibition of Cannabis.

So far, I hope you’ve picked up two things about homemade carbon filters:

(a) They aid in the removal of the aroma created by the terpenes/ terpenoids of your bud plant.

(b) Depending on where you live, diy activated carbon filters may ultimately keep the neighborhood free of the smells of your grow operation and, by extension, help keep you out of the purview of the law.

But how do they work? How do homemade carbon filters remove the smell from the air? With what effectiveness? Is there multiple types of DIY carbon filters? Do you have to use activated carbon when making homemade carbon filters? Can you use charcoal?

How It Works

I don’t know about you, the fact that I don’t know how they get the smell into a candle, fleeting though it is, consistently vexes me. In fact, this is just one example of many on how little I know about smell. So when I had heard about something akin to charcoal being effective in ‘scrubbing’ the aromatic profile accompanying your growing cannabis, I was curious as to how.

DIY Activated Carbon Filters and Terpenoids

Terpenoids are, simply put, terpenes that have gotten a bit of oxygen. So what then, is a terpene?

A terpene is an aromatic organic hydrocarbon, or molecule made of carbon (hint hint…) and hydrogen, and they are responsible for the plant’s smell profile. As noted above, during the bud curing process the terpenes are chemically converted into terpenoids by oxidation, or exposure to air.

Homemade carbon filters work by trapping the hydrogen and carbon molecules within the gaseous oxygen making up our atmosphere by a process of adsorption. By forcing the grow room air though your DIY carbon filters, through adsorption, oxygen will be the only remaining molecule able to reach the outdoors.

How to make your very own homemade carbon filter

Alright, now that you better understand how DIY activated carbon filters ‘scrub’ the air of organic aromatics it’s time to share two methods of building a DIY carbon filters. The first method is more suited for the smaller operations among us, while the second may be better suited for the needs of a multi-plant parent.

Homemade carbon filters, while effective, are only as effective as their partner, ventilation. In most cases, you’ll want your exhaust fan to match the strength of your DIY activated carbon filters. If you have an exhaust fan that blows air at 300 CFM (cubic feet per minute), you’ll need your homemade carbon filters to be able to filter at least that. For the homemade carbon filters, this is a trial and error period where you’ll be adjusting the amount of activated carbon till you don’t smell your plant children.

Small Set-Up DIY Activated Carbon Filters

What you’ll need:

• Duct tape
• A Large-ish Pencil Cup
• A small-sh Pencil Cup
• Pantyhose
• Activated Carbon

How it’s done:

• Begin making your DIY carbon filters by pouring about an inch of activated carbon into the larger of your two pencil cups, making it so that when you place the smaller cup within, the two are level with each other.
• Slip the smaller cup into the pantyhose. Place the smaller cup into the bigger cup.
• While holding the end of the pantyhose, pour the activated carbon gently over the top, allowing it to roll down the sides of the smaller cup. In effect, this should fill in the space between the two cups with the activated carbon pieces.
• Once the walls are filled and the smaller pencil cup is held firmly in place, fold the pantyhose over the outer, large cup, tying the end.

For those of you that are more visual, check out this link for some step-by-step photos.

High Flow DIY Carbon Filters

As the name suggests, homemade carbon filters of this variety are meant for the indoor cultivator with more than enough room. DIY activated carbon filters of this type require a larger ventilation system, as well as stronger exhaust fans to accommodate the larger air volume.

What You Need:

• 5 Gallon Bucket
• 4 Gallons of Activated Carbon
• Filter Pad
• 3-4ft of PVC w/ an endcap, diameter of 4-6in (should match rest of ventilation)
• Duct Tape
• A Drill
• Zip-ties

How it’s Done:

• Use the drill to punch holes into the bucket. The more holes, the better the oxygen can escape. Measure how far the PVC goes into the bucket, and drill holes in that section of the PVC pipe. YOUR PVC SHOULD ONLY HAVE HOLES WHERE IT WILL BE SUBMERGED WITHIN THE BUCKET.
• Next, your DIY carbon filters require you to wrap the outside of both the bucket and PVC pipe with the filter pad, cutting to size. Use the zip ties to secure the filter pad snuggly around each item.
• Put the PVC endcap on the side with the holes. Place the endcap side of the PVC into the center of the bucket and begin pouring the activated carbon into the DIY carbon filters, filling the space between the bucket and PVC pipe. Cut a hole in the bucket lid that the PVC pipe can fit through.
• Duct Tape the lid to the PVC, sealing all the cracks that air may escape try to escape though.

Again, for those of you who like photos with your step-by-step, check this out.

And that’s how you can make DIY carbon filters at home.

By Joey Wells