What Activated Carbon Really Filters (And Why Cardboard Alone Won't Cut It)

Why a paper tip alone won't cut it, and why the combo of fiber and activated carbon is what actually makes your joint smooth.

By Dr. Hybrid (Andreas Setzer) · ⏱️ Reading time approx. 8 minutes

The second you spark a joint, hundreds of different compounds form. You see a few of them after the session as brown gunk stuck in the filter. The biggest chunk you never see. And it's exactly that invisible part that's the bigger problem long term.

There are a few myths floating around the community about which filter can do what. We're going to look at what the studies actually say. Explained so it makes sense, no blown-up marketing promises.

Three kinds of nasties in the smoke

Three different types of pollutants are floating around in your joint's smoke. Sounds like a detail, but it's key: each type has to be filtered differently.

• Tar and ash: the big, sticky particles. The stuff you see in the filter.
• VOCs: tiny, invisible gases.
• Carcinogens like benzene: also invisible gas. Small and seriously nasty.

Whether a filter holds something back or not comes straight down to one thing: is the compound a particle or a gas?

Tar: the stuff you can see

Tar is everything sticky and solid that's left over when things burn. The brown stuff in your filter. The stuff that wrecks and sticks the inside of your bong.

Tar particles are big enough that a simple paper tip catches part of them. They just get stuck on the fibers, like breadcrumbs on a dish towel. It's mechanics, no magic.

Meaning: a paper tip isn't totally useless. But it's not the whole story either.

VOCs, what even are they?

VOC stands for "Volatile Organic Compounds". Sounds clunky, but it's easy to grasp.

Picture opening a can of fresh wall paint. That sharp smell that hits you, those are VOCs. Same deal with glue, solvents, permanent markers or petrol. Compounds that escape into the air as an invisible gas at normal room temperature.

When you smoke, they form through combustion. And while the tar collects in the cardboard (paper) filter, these gases just sneak straight through.

What else is in the smoke, and why it hurts

A Canadian study by Moir et al. (2008) put the smoke of cannabis and tobacco joints under the microscope and compared them. Among other things, they found:

• Benzene: the WHO says: carcinogenic to humans. Full stop.
• Hydrogen cyanide: even higher in cannabis smoke than in tobacco smoke.
• Acrolein: one of the strongest respiratory irritants there is.
• Formaldehyde, acetaldehyde, 1,3-butadiene: all carcinogenic.

Quick word on "carcinogenic", because it often just gets thrown around as a scare word: carcinogens wreck the DNA in your cells. DNA is like the build manual for every cell. If something keeps getting damaged year after year, some cells start growing out of control. That's how tumors form. With smoking, it mainly hits the lungs.

But cancer is the long-term story. You feel these compounds short term too, right after the first few puffs:

• Scratchy throat the next morning
• Coughing when you inhale
• Burning eyes
• Furry taste in your mouth
• That feeling that the joint pulls "harsh"

All of that is irritants in action. Acrolein, for example, irritates your mucous membranes so hard that your body fights back with a cough.

A cardboard filter holds these gases back about as well as a fly screen holds back the wind. Meaning: not at all.

Where activated carbon comes in

Activated carbon works completely differently from cardboard. It doesn't filter mechanically, it traps pollutants on its surface, like a sticky inner wall. The experts call this adsorption: the molecules stick to the surface instead of soaking into the material.

It works because of one absurd property: a single gram of good activated carbon has an inner surface area of around 1,000 m². That's the size of a tennis court, folded into a few millimeters of filter. Sounds crazy, but it's measured reality.

Picture activated carbon like a microscopically tiny sponge. Only instead of big holes like a normal sponge, this one has millions of tiny tunnels and chambers, all connected. When the smoke flows through, two things happen:

• The small gas molecules (benzene, formaldehyde, acrolein) are exactly small enough to fit into the tunnels.
• Inside, they stick to the walls and don't come back out.

Bigger stuff can't even get through the tunnel entrances. That flows past on the outside.

The result: activated carbon is pretty picky. It grabs the small gas pollutants specifically, exactly where cardboard is completely useless.

How much an activated carbon filter really filters

Activated carbon in filters is nothing new. The cigarette industry has been researching it for decades. A few concrete numbers from the published literature:

(Studies: Gaworski et al. 2009, Polzin et al. 2008.) Exactly how much your filter pulls off depends on the type of carbon and the processing. But the direction is the same.

Activated carbon has a weak spot

Now let's be honest: activated carbon is a boss with gases. But it can't do much about the bigger tar particles, they're too fat for its tunnels.

Cardboard, on the other hand: catches a bit of the tar. With the gases: zero chance.

Sounds like a dilemma. That was our starting point for building Hybrid Filters. Instead of picking a side, our filters just combine both:

• Fiber at the ends mechanically catches the tar particles and the fine dust.
• Activated carbon in the middle swallows the invisible gases.

Two different problems, two different solutions, united in one filter. That's exactly what Hybrid is for. (More details and lab data are on our technology page.)

"But doesn't activated carbon filter out the THC too?"

This line is making the rounds in the community right now. Some prominent voices from the rolling-papers world claim that activated carbon filters out the active compounds along with the pollutants.

Spoiler: nope. And that's not a marketing claim, it's clean chemistry. Let us explain why.

In the smoke, THC and CBD don't fly around as single molecules. As soon as the hot smoke cools down, they clump together with other oily compounds into tiny droplets. They travel through the joint not as a gas, but as a fine mist of oily mini-droplets.

So you can really picture it, there are three size classes moving through the smoke:

• Tiny: gas molecules like benzene, acrolein, formaldehyde. Fit perfectly into the tunnels of the activated carbon. Get caught there.
• Big: tar and fine-dust particles. Too fat for the activated carbon tunnels, but big enough that the fiber holds them mechanically.
• Right in between: the oily THC and CBD droplets. Too big for the activated carbon tunnels. Too small for the fibers. They slip through.

Cannabinoids travel mostly particle-bound, meaning attached to tiny tar droplets. These droplets sit in the micrometer range, the tunnel entrances of the activated carbon in the nanometer range, roughly a thousand times smaller. A THC droplet simply doesn't fit in there. Picture trying to push a tennis ball through a keyhole.

So activated carbon is no "blanket pollutant killer". It's super picky. And the Hybrid system uses exactly that pickiness on purpose: the gases get caught, the cannabinoids come through.

(Mechanism behind it: Branton et al. 2009.)

What's left at the end

A good filter has to pull off two things at once: catch the invisible gases AND hold back the visible particles.

And the active compounds? Swim right through, exactly where they belong.

If you don't care what you inhale, a cardboard tip does the job. If you'd rather not marinate your lungs in carcinogens long term, the combo is the smarter move.

One honest thing before we wrap up

We don't sell miracle cures. No filter on earth makes smoking healthy. Filters are a harm-reduction tool, they reduce the damage, they don't cancel it out. Way better than nothing. But no free pass.

So what about the criticism from High Times?

Back to why we're here. At their core, the High Times articles run one argument: activated carbon mainly removes terpenes, barely any tar. The smoke tastes weaker as a result, you pull more often and deeper, and end up dragging even more tar into your lungs than with no filter at all. The newer article even slaps a number on it: 86 % more tar.

There's something to the basic chemistry, and it lines up with what we explained above: activated carbon preferentially binds gases, tar tends to stick to mechanical fibers. A pure activated carbon filter with no mechanical component really does pull out barely any tar. So far, so correct.

Except a headline gets built out of that true core that the chemistry doesn't actually support. That's misleading, in four places:

1. The 86 % is calculated, not measured.

Look at how the number comes about: you assume the filter weakens the active compound. Then assume you smoke twice as much because of it. And multiply that by the low tar reduction. There's your "86 % more". The sticking point is the doubling, and that comes from nicotine research. Nicotine is physically addictive and holds a tight dose setpoint, which is why cigarette smokers compensate. For cannabis this effect isn't proven, and the article itself admits the cannabis-specific study is missing. So an unverified assumption turns into a percentage in the headline.

2. Tar mass isn't the same as tar harm.

The article measures "tar" as a single lab number, making exactly the mistake it accuses the tobacco industry of. What acutely damages the lungs and airways isn't the grams of tar, it's the free radicals, aldehydes and carcinogens in the gas. Those are exactly what the activated carbon grabs. The tar mass barely moves, the biological toxicity per pull drops significantly. Both are true at the same time, the article just leaves out the second half.

3. "Activated carbon filter" isn't "Hybrid".

The whole criticism targets pure activated carbon with no mechanical filter body. The article even admits itself that cotton and paper catch particles mechanically. And that's exactly the build of a Hybrid filter: fiber at the ends against tar, activated carbon in the core against gases. The weak spot being criticized applies to a filter design that isn't even on the table here.

4. A contradiction in itself.

The article claims two things at once: the filter pulls off so much active compound that you smoke twice as much, and it barely touches particles (so tar and the particle-bound THC). Both together can't work. If THC slips through particle-bound, then the exact active-compound loss that's supposed to drive the doubling in consumption is missing. The argument saws off the branch its own math is sitting on.

Bottom line: the valid core of the criticism hits pure activated carbon with no mechanical filter body. It doesn't carry over to a combined build.

"Do I smoke more with an activated carbon filter?"

Short answer: there's currently no cannabis-specific data on that, only an analogy from tobacco research. With cigarettes that use pure activated carbon filters, some studies did observe compensatory smoking, weaker taste, more or deeper pulls. Whether that carries over one-to-one to cannabis, and specifically to a Hybrid build with a fiber component, hasn't been studied. So the concern doesn't really hold up.

The smooth combo for your joint

This exact combo sits inside our Hybrid Supreme Filters: fiber against tar and particles, activated carbon against the invisible gases. Lab-tested: 38 % fewer pollutants than conventional activated carbon filters without a fiber cap. No clogging, even in the cold, full flavor. Just smooth. Treat yourself.

Free 3-pack sample See all filters

Sample pack via newsletter only. Free shipping over 40 euros in AT and DE.

Studies & sources

• Moir, D. et al. (2008): A comparison of mainstream and sidestream marijuana and tobacco cigarette smoke. Chemical Research in Toxicology, 21(2), 494-502.
• Gaworski, C. L. et al. (2009): Effect of filtration by activated charcoal on the toxicological activity of cigarette mainstream smoke. Inhalation Toxicology, 21(8), 688-704.
• Polzin, G. M. et al. (2008): Effect of charcoal-containing cigarette filters on gas phase VOCs. Tobacco Control, 17(Suppl 1), i10-i16.
• Branton, P., Lu, A. H., Schüth, F. (2009): The effect of carbon pore structure on the adsorption of cigarette smoke vapour phase compounds. Carbon, 47(4), 1005-1011.
• Goel, R. et al. (2018): Effect of Charcoal in Cigarette Filters on Free Radicals in Mainstream Smoke. Chemical Research in Toxicology, 31(8), 745-751. (Incorrectly attributed as "Hoffmann 2018" in the High Times articles.)
• Coggins, C. R. E. & Gaworski, C. L. (2008): Could charcoal filtration of cigarette smoke reduce smoking-induced disease? Regulatory Toxicology and Pharmacology, 50(3), 359-365.
• U.S. National Cancer Institute (2001): Risks Associated with Smoking Cigarettes with Low Machine-Measured Yields of Tar and Nicotine. Smoking and Tobacco Control Monograph No. 13.
• IARC Monographs Vol. 120 (2018): Benzene, Group 1 carcinogen.