Carbon Filters To Control The Smell Of Cannabis
2 min

How To Use Carbon Filters To Control The Smell Of Cannabis

2 min

A carbon filter may not look like a valuable investment on the surface, but it's an essential part of the discreet cannabis grower's arsenal—regardless of experience or setup. To find out what, exactly, a carbon filter does, and how to make your own, keep reading.

Why use a carbon filter when growing cannabis?

Why Use A Carbon Filter When Growing Cannabis?

Marijuana may smell fantastic to growers and enthusiasts, but its aroma can easily overpower a small grow space. Moreover, left unchecked, 2–3 plants can produce enough smell to tip off neighbours to your extracurricular activities. If this sounds like a situation you wish to avoid, it's time to invest in a carbon filter.

Essentially, a carbon filter works to filter out the aromatic compounds emanated by cannabis buds. By “scrubbing” these molecules through activated carbon, the smell of your beloved cannabis plants stays contained within your grow tent or room. Carbon filters are a cheap, simple, and highly effective way to ensure your neighbours (or anyone for that matter) remain none the wiser.

How well do carbon filters remove the smell?

How Well Do Carbon Filters Remove The Smell?

So long as the fan and filter are an appropriate size, and the grow room/grow tent is otherwise sealed, then carbon filters are capable of removing every aromatic trace of your grow. To ensure this efficiency, you have to set everything up properly, make sure that the smell can’t leak out through some other exit, and replace the filter regularly enough that it doesn’t become full (it should last a few harvests before requiring replacement).

Where to put a carbon filter in your grow room?

Where To Put A Carbon Filter In Your Grow Room?

Depending on your setup and the space available to you, you will end up placing your carbon filter either inside or outside of your grow space.

Inside the grow tent

If your tent is big enough, then placing the carbon filter at the beginning of the ducting is a great choice. This means that all of the air pulled through the exhaust system will be filtered before going anywhere, minimising the risk of leaks.


  • Complete and efficient
  • Minimal risk of leaks


  • Requires a suitably large tent

Outside the grow tent

Outside The Grow Tent

For many with a small-scale growing operation, placing a carbon filter inside a grow tent may not be an option. In this case, it will have to be attached to the ducting outside the tent. This is less efficient than placing it inside the tent, but it does mean that growers can get away with using smaller tents, which can be beneficial—or even essential.

If you place the filter at the end of your ducting, then you have to be doubly sure that the ducting is completely sealed to make sure that no smell leaks out.


  • Requires a smaller tent


  • Not as efficient as placing it inside a tent

How to make a DIY carbon filter

How To Make A DIY Carbon Filter

Making your own carbon filter is actually surprisingly easy. At first thought, these pieces of kit might seem fairly high-tech. In fact, they’re actually pretty simple, and basically just consist of activated charcoal held within a mesh body, and covered by a pre-filter.

Below, we’ll show you how to make one.

Equipment for DIY carbon filter

Equipment For Diy Carbon Filter

  • 2 mesh pencil holders (or waste paper baskets, for a larger filter). One pencil holder should be three-quarters the size of the larger one. The larger one should have the same diameter as the flex duct used for your ventilation system.
  • PVC piping
  • Tights/nylon knee-high socks (these will act as the pre-filter)
  • Finely ground activated charcoal
  • Scissors
  • Drill and drill bit (optional)

DIY carbon filter: step-by-step instructions

DIY Carbon Filter: Step-By-Step Instructions

  1. It may be the case that the bases of your pencil holders are not mesh. In this case, drill 8–12 evenly spaced holes in the bottom of each.
  2. Insert each pencil holder into a separate knee-high sock. Put the base of the pencil holder in first.
  3. Fill the larger pencil holder halfway with activated charcoal.
  4. Place the smaller pencil holder inside the larger one, and adjust the height of the inner pencil holder until its rim is level with that of the outer holder.
  5. Fill the space between the two holders with activated charcoal.
  6. Secure the two together using the socks.
  7. Attach your PVC ducting and inline fan to the opening of the outer pencil holder.

Maintaining a carbon filter

Honestly, maintaining a carbon filter couldn't be more straightforward, as there isn't any maintenance required! If you've gone with the DIY option, and the filter's sealed correctly, you can leave the carbon filter to do its thing. A solitary carbon filter is more than enough for several grows. Once you notice the smell of cannabis building, it's time to think about changing the filter altogether, or replacing the carbon/filter element inside.

Max Sargent
Max Sargent
Max has been writing for over a decade, and has come into cannabis and psychedelic journalism in the last few years. Writing for companies such as Zamnesia, Royal Queen Seeds, Cannaconnection, Gorilla Seeds, MushMagic and more, he has experience in a broad spectrum of the industry.
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