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How to Set Up a Carbon Filter for Ideal Odor Control

Grow rooms need good ventilation to keep cool, fresh air coming in and warm, moist "used" air going out. But indoor growing can produce unwanted and even potentially toxic odors and contaminants from soils, fertilizers and the plants themselves. Since the exhaust air often flows into an adjacent indoor area, adding activated carbon filters to your airflow system is the best way to control odors and contaminants. Here's how to set up a carbon filter for ideal odor control to clean your air while maintaining efficient airflow.

The place for your filter is in the exhaust system. Can-Lite activated carbon filters mount easily to Can-Fan and Max-Fan exhaust fans for long-lasting, consistent filtering performance with minimal resistance to cause airflow loss. Can-Lite fans and filters can be hung from grow tent supports or attached to solid surfaces in rooms with walls or ceilings.

The filter should be mounted on the intake side of the fan to remove contaminants before they reach the fan housing. Can-Lite filters come with pre-filters to keep dust, mold, and other particles from clogging the activated charcoal in the filter itself, so you should be pulling air through the filter rather than pushing air into it.

You may have both supply and exhaust fans, depending on the size of your grow operation. Even smaller rooms or tents that draw fresh air from the surrounding area may need an exhaust fan to carry away hot, stale air and an intake vent or fan to bring in fresh. Ideally, in an enclosed grow space the fresh air supply will be near the bottom of the area and the exhaust will be near the top. This takes advantage of the fact that hot air rises and cooler, denser air accumulates lower. As the warm, moist air is exhausted, fresh air will flow in across the plants to take its place.


It isn't necessary to have the air being pulled through the carbon filter exhausted outside your growing area; depending on your setup it may even work better to have the filtered air returned immediately to the growing area. This can be accomplished by mounting the carbon filter to the intake side of the fan with a rubber coupler or ducting and placing it inside the growing area without ducting the fan's output out of the grow. In this way, the carbon filter will continuously "scrub" the air in the growing area to remove odors.

Depending on your particular setup, fans and carbon filters can be attached to flexible ducting, rubber coupler, or rigid pipe, and can be mounted either inside or outside the grow area.

Can-Lite Carbon Filters are the highest-quality grow room air filters available and come in 4" and 6" duct sizes to match your ventilation needs; the filters are sized to fit the fans.

Black Dog LED has what it takes to make it easy for even inexperienced growers to get started. We offer individual grow lights, grow tents up to 10'x10', and indoor grow room supplies like Can-Fans and Can-Lite filters, as well as complete LED grow room kits with footprints ranging from 2'x2½' to 9'x9'.

Our website has a comprehensive selection of products for all types and sizes of indoor growing operations. You'll also find plenty of information about the benefits of LED grow lighting, too. While you're here, take a look at our photo gallery to see for yourself the amazing results you can achieve with Phyto-Genesis Spectrum™ grow lights from Black Dog LED.

15 thoughts on “How to Set Up a Carbon Filter for Ideal Odor Control”

  • Melissa

    I've got a room 11 ft x 18 ft x 7 ft tall. Putting your 4x8x6'" in there. Using max fan with carbon filter to vent outside. Do I need an inlet fan as well for fresh air or will I be fine with just an outlet fan???

    • Noah

      Hi Melissa, great question. You will need what we call a "passive intake" where you use a length of ducting (not too long) to pass air through one of the duct ports into your tent. This will allow for make-up air to enter. The fan should exhaust from a port at the top and the intake should be a port down low. We hope that answers your question, please let us know if you need further clarification.

    DAVID PAZANDAK March 9, 2017 at 12:00 pm

    Given 8'x3'x3' grow tent and Phyto-Max 2 400 light, what are the proper heights to be maintained to the cannabis canopy top for the veg and flowering stages ? Thanks, Dave

    • Amanda Herman
      Amanda Herman May 20, 2019 at 6:00 am

      Hello David,
      Thanks for the question! We have an extremely helpful calculator on our site for this exact problem! Here is a link to that:
      Simply put your information in and it will let you know!

      Happy Gardening,

  • Forest


    I have my carbon filter as shown in your pic, but in another room ducted through a wall. My question is does the carbon filter I have a 200mm neck Mountain Air, need to be horizontal or vertical ? Does it matter ? Also does it need space can it hide behind stuff etc ?


    • Noah

      Manufacturers recommend you suck through the filters so you should have the filter in your grow space if possible, sucking air through it. Then you can run a duct from the fan exhaust to the other room and exhaust it there. Do not make the duct longer than it needs to be. I am not sure what you are asking about a "200mm neck Mountain Air".

  • Chris Nagle

    Is it ok to attach a carbon scrubber to my intake as well as my exaust .i would also like to keep filters outside the tent can that be accomplished properly.

    • Noah

      Generally manufacturers recommend you suck air through filters, not blow out through them. So it is best to suck through the filter and exhaust the filtered air into your space. If you put two filters on one fan I would even worry about overheating a fan. We do recommend setting up a second fan/filter combination in the room outside the tent if you want to truly eliminate smell. The fan in the tent will kill 90% plus of the smell and the second fan/filter will get rid of the rest.

  • Robert

    If setting up a second fan/filter outside of the grow tent for maximum odor control, how should that fan/filter combo be setup in relationship to the exhaust ducting from the tent?

    • Noah

      This works best if you have the tent set up in a room with the door closed. Then you can put it just about anywhere and it will circulate the air. For simplicity and assuming you have the space, we just set the filter on the ground and set the fan on top and let it run. If you need more space you can hand the whole thing, in which case we use a small length (12") of the appropriate ducting to connect the two and hang them individually.

  • Donald Edward Harris
    Donald Edward Harris April 16, 2018 at 9:55 pm

    When unwanted air is passed through the carbon filter does the unwanted odor go any farther than the carbon filter?

    • Noah

      It depends on how new the carbon filter is, how good of quality it is, and how much smell there is. We only sell one brand, Can-Filter since they are top quality. They last a long time and we often get up to two years off a filter before it begins to fail. However, if you use a small filter to tackle a lot of smell it will not handle all of it and some odor will escape.

  • Tom

    This is the first time I've seen the idea of not exhausting air but just scrubbing it inside the tent. Since my winter grows are in an uninsulated basement, I'm looking at ways to keep my temperature up rather than down and keeping the tent sealed is one way. My concern with not exhausting is humidity and plant diseases. Will the recirculation of air through the filter help with this, in addition to odor control?
    I checked can filters and noticed they recommend different filters for the same fan depending on their use, recirculation or exhaust. Do you know why?

    • Noah

      Hello Tom,
      Good question. In the table on their site there is a note about recirculating numbers (top right corner of the table) where they clarify that the recirculating numbers are double whatever the exhaust numbers are. If you look at our fan/filter pairings in our kits you will see we cover the recirculating numbers.
      Happy gardening,
      Black Dog LED

  • Graham Smith

    I only just found this site after searching for info on fan set ups. Thank goodness I did as the Q &A are superb and condensed in one place so I found out everything I was wanting an answer for. This site is now in my favourites. Thanks all.

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