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1. Using Carbon Filters In a Grow Room

So, after months of research and contemplation, the time has come to set up your first indoor grow space. You’ve probably chosen a lighting rig, a tent, and most of the associated accouterment – and hopefully found the seeds that tick all boxes.  

But what about the carbon filter for your grow tent or room?

Carbon filters are often the last piece of kit novice growers focus on, but they truly are an essential addition to any grow room. Carbon filters are absolutely necessary for helping you not only control the stank of your plants but are also pretty vital in maintaining a clean, healthy, and consistent grow room environment.

Keeping the climatic conditions under your control will go a long way toward producing the type of yields and potency you’re dreaming of, and while the world slowly turns towards cannabis legality, the vast majority of new growers still need to keep those delicious fragrances under wraps. Carbon filters are your best ally here.

And while a basic understanding of carbon filters is essential, there are still many nuances to consider when choosing the right one for your grow room. Enough babble, let’s dive headfirst into it.

What Are Charcoal or Carbon Filters, And How Do They Work?

As the name suggests, carbon filters are a type of air purification system that uses activated carbon to adsorb and filter out odors and pollutants. An activated carbon filter works by trapping the molecules within its tiny pores, preventing them from passing through. In the context of a grow room, this refers to both aroma and potentially harmful particles in the air that can lead to both mold growth and plant viruses.

Constructed from metal cylinders that are filled to the brim with activated charcoal, carbon filters do a great job of removing and neutralizing airborne particles. Activated charcoal is a porous material. These pores massively increase the surface area, which gives the charcoal a much higher capacity to adsorb odors than other materials.

Adsorb? Don’t you mean absorb?

Nope, no typo here friends. Adsorption and absorption are two separate processes.

Absorption is when the molecules of the substance being filtered are actually taken into the material, and adsorption is when those molecules bind to the surface of the filter material instead.

So basically, activated carbon works not by trapping particles inside itself, but by binding them to its surface area. This means that, unfortunately, once your carbon filter starts to fill up with odor molecules, it’s time to invest in a new one or else risk the delectable, dank stank leaking out of your grow area.

Anyway, the huge surface area that activated charcoal provides means that it can trap and remove significantly more pollutants, gases, and odor molecules than competing materials, making them the only real choice for indoor cannabis cultivators. This might seem a little far-fetched, but a single gram of active carbon has a surface area of up to 2000m². 

Carbon extractor for a cannabis grow room

They work by being connected to the fan and ducting system of your grow space, with the exhaust fan pulling air through the filter and passing it over a large section of the activated carbon. This forces the air to pass through the filter multiple times, significantly reducing the number of particles and pungent aromas that can escape into the environment.

The Benefits of Using Carbon Filters

Aside from the obvious benefit of eliminating unwanted odors, there are a number of reasons why carbon filters are an invaluable piece of equipment for a grow room:

  • Controls Humidity and Temperatures:. Carbon filters will help you control the levels of humidity in your grow space, in addition to controlling temperatures. This helps you maintain ideal climatic conditions for maximum yields and the highest cannabinoid production possible.
  • Prevents Mold and Mildew:  Carbon filters also act as a barrier between mold spores and your plants, helping to prevent the spread of any form of mold or mildew that may enter your grow room.
  • Reduces Risk of the Crop Having to Battle Disease Issues:  Carbon filters will help reduce the spread of viruses and diseases from one plant to another, ensuring healthy yields with minimal risk.

Choosing The Right Carbon Filter For Your Grow Room

When it comes to buying a carbon filter for your grow room, there are a few key points you need to consider.

First and foremost, as we just mentioned above, activated charcoal filters have a limited lifespan. Once they are done, they’re really done.

How long do grow room carbon filters last?

That’s a tricky question to give a comprehensive answer to, as there are a bunch of variables that need to be taken into account, such as the size of your grow space and the type of filter being used. In general, a well-made carbon filter will last between 12 to 18 months. Many companies state that you need to change them every 6 to 12 months, but we find they do last a little longer, for the most part. You’ll know it is done when the smell starts to become more apparent outside of the growing area.

There is a wide range of grow-room carbon filter options out there, and they are anything but equal. 

As with most things in life (and especially with cannabis cultivation equipment), it pays to get the best option in your budget. Sure, you could grab a really cheap option online, but these will either fail within a few months or not even work from the get-go. Best to grab a slightly more expensive carbon filter, to begin with.

Choose One That’s The Right Size For Your Grow Room

There are two important factors to consider when choosing a carbon filter for your grow tent – the volume of the grow tent itself, and the cubic feet per minute (CFM). needed to perform proper air exchange. It’s simple math:

  • To find the volume of your grow area, multiply the height, width, and length of the tent or space – say you have a 8 x 8 x 6 foot tent, this would equal 384 cubic feet.
  • Then all you have to do is divided that number by the number of minutes you want for full air exchange in the grow area – 1 to 3 is ideal.
  • So 384 divided by 2 = 192
  • The CFM of your grow area is 192. Just make sure that your exhaust fan and grow room carbon filter meet or are in the vicinity of this number and you’ll be all gravy.

If you have any doubts about your choice, head down to your local hydroponics supply store. The guys and gals there usually have a pretty good understanding of all this, and will definitely be able to point you in the right direction.

Setting Up Your Grow Tent Carbon Filter

Right, you’ve done the relevant calculations, and bought the carbon filter of your dreams. Now it’s time to set the damn thing up!  

Again, this is all pretty simple.

Cannabis tent with carbon filter
  • First up, connect the filter for your grow tent to the exhaust fan. You’ll need to also ensure the ducting is the correct diameter to meet the CFM requirements, but as long as it fits the fan and filter you should be fine. Use some duct tape to ensure no air leaks. We recommend investing in some soundproofed ducting
  • The filter is connected to the intake of the fan. This can be done with ducting, or directly to one another. If you are using a cooling hood for your light then connect that between the filter and the intake of the fan.
  • The ducting is then run from the fan exhaust out of the grow space and to a ventilation area. This can be a window, bathroom fan, etc.
  • Hang the filter from the tent roof supports, as high as possible. It’s best hung in one of the corners to help keep the tent as free from cluttered space as possible. And that’s it!


Carbon filters are, without a shadow of a doubt, the very best option for growers looking to neutralize the pungent and spicy aromas that come hand-in-hand with cultivating cannabis indoors. While there are separate options for covering up the stank – like air purifiers and perfumed household sprays – it’s always recommended that you install grab a high-quality carbon filter for every indoor cannabis garden. 

Not only will it keep that secret garden of yours more under wraps, but it’ll also reduce the chances of annoying issues plaguing everyone’s favorite crop. Good luck, and enjoy the ride!

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Sam North

Sam North is a content writer with a passion for everything cannabis. After working multiple seasons on weed farms absorbing the ins and outs of cannabis cultivation and culture, he decided to transition into a role that would allow him to work from anywhere, anytime. Sam now writes for multiple weed publications. He has extensive experience with a wide range of canna-agriculture styles, from smaller artisanal farms to large-scale commercial operations, and is here to share his knowledge to give you all the best chance of cultivation success.

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