Carbon Filters for Grow Rooms Explained

The use of carbon filters in cannabis growing is a relatively new practice, especially here in Spain. I still remember going over to my friends’ place and finding out they didn’t have carbon filters in their grow tent – their entire neighborhood would stink. Thinking back on it, it was kind of crazy – but growing cannabis indoors was also still a relatively new idea at the time. Nowadays, pretty much anyone knows that you need a carbon filter for a grow room to stay discreet and operational.

carbon filter for grow room


Carbon Filter for Grow Room | Intro

carbon filter for grow roomNowadays, odor filters are one of the most important parts of growing cannabis indoors – cannabis plants let off intense aromas, even when growing, and everyone knows what it smells like now. Once they begin to flower, they really begin stinking the place up – if you don’t have any way to mask the smell or filter it, you may end up having issues with your neighbors and even the authorities.

To stop this from happening we’re going to give you a run-down of some of the best ways to filter cannabis odors – active carbon filters. These filters are here to stay and are the most-used method to get rid of cannabis odors in indoor grows; they’re super easy to use and install. You’ll need to keep a few parameters in mind when installing your filter. Keep reading to find out how they work and what you need to know before getting one.

What’s a carbon filter?

It’s all in the name – odor filters essentially get rid of any odor or aroma that passes through them, although some types of filters can also get rid of toxic particles.

When we say filter, you might be thinking of a typical fish tank filter; an extractor fan with some sort of cover on one end of it such as a sponge or  a simple cloth cover. Well, it’s a similar system; odor filters are usually made out of polyester or spongey fibers, as well as other types of porous materials, as well as activated carbon.

What’s activated carbon?

Carbon or charcoal is a naturally absorbent material thanks to how porous it is, even without being activated. When activated it is one of the most absorbent materials on earth, used to filter both air and water. It can absorb almost any type of material although it works best with natural or organic elements.

coco used to make active carbonActivated carbon is made using various different types of wood and fruit casings like coconut. Shells or wood are first carbonized at temperatures over 400°C, they’re treated again at over 800°C while being treated with vapor to open up micro-pores and increase absorption rates.

Activated carbon can be found in various formats; powdered, in granules and in pellets. Depending on the format, it can be used to filter air, gas or water. Activated carbon (or charcoal) is also used in cosmetics, for food purposes and for treating cases of severe intoxication.

Activated carbon uses:

  • Water purification (osmosis filters, fish tanks etc.)
  • Air purification (vents, air conditioners etc.)
  • Odor filters (extractor fans, filters for growing cannabis etc.)
  • Gas filters (gas masks, polluted areas etc.)
  • Cosmetics (cleansers, makeup removers etc.)
  • Dietary supplement (although there are side effects)
  • Can treat intoxication

Activated Carbon Filter for Grow Room

Activated carbon filters come in various different formats. For example, the filters used in cooked tend to be thick plaques that contain porous fabrics that have been enriched with activated carbon. When it comes to carbon filters for ventilation ducts, they come in boxes which have various strips of that same fabric and activated carbon. However, cannabis filters come in a tubular container and contain a special amount of activated carbon pellets or granules.

Home-grade filterActivated carbon filters for cannabis are known for their cylindrical, tube shape as well as their double layering of activated carbon, designed to make any air that flows through it go through the activated carbon for the best possible filter. It has a large amount of holes on the outer layer that allows for maximum air flow.

Carbon filters for cannabis growers tend to come in a sort of sock which stops any dirt from getting in and obstructing the air flow, which would reduce the amount of odor filtered and could be incredibly damaging for your plants. This increases the lifespan of your filter, allowing it to stay functional until the last gram of carbon is used up.

How to correctly install a carbon filter for your grow room

It’s not that hard to set up an odor filter in a grow tent, although you’ll need to keep in mind the weight and size of the filter itself – it needs to be as high up as possible for the best results. Once you have your filter and a good friend to come help you set it up, it’s time to get started.

Step 1: If growing in an indoor tent, you can simply attach it to the aluminum or steel bars at the top of the tents’ structure, using the straps that the tent should already have to keep it steady. This can be done simply, without the help of anyone else.

If you’re working in an open room, you’ll need to put holes in the ceiling and use eyebolts (the size depends on how hefty a filter you have). You can use chains or super strong pulleys to hold it up. You will most definitely need help from a friend to set this up.

Step 2: The next step involves attaching your aluminum or soundproofed ducting to your filter – make sure to get the right sizes or you’ll be quite disappointed. The ducting then needs to go all the way to the air extraction system or to your cooltube and then your extraction fan if you’re using a cooled lighting system.

Step 3: All you have left to do is connect your extraction fan to the outlet you previously made (in your room) or the extractor fan outlet in your grow tent. Now, all you have to do is turn your extraction fan on and make sure that there are no leaks – you’re ready to grow!


carbon filter for grow roomLastly, you’ll also need to do regular maintenance on your filter system just to make sure that it’s working properly. You’ll need to periodically check the odor sock and the activated carbon inside. We recommend removing the sock every two months in order to wash it or simply replace it if it’s seen better days – make sure to check the carbon too, you don’t want it compacting inside. The best way to do this is placing it upwards on the ground and hitting it a couple of times lightly to make sure the carbon is moving around inside there.

Carbon filter troubleshooter

Carbon filters can cause a few issues when not used correctly, although some certain parameters and environmental conditions in your grow room can also affect them negatively.  If your carbon filter starts acting up, you’ll know because of the smell. In order to avoid any issues, we recommend keeping the following information in mind:

  • Carbon tends to become compact when relative humidity is high, around 75-80%, and once it begins to compact it’ll stop filtering correctly. It stops air from being able to pass through, which means any odors will be going straight back out into your grow room.
  • When carbon compacts, it makes it incredibly hard for any air to pass through, which means that your extraction fan is probably going to have to work overtime and it may end up breaking due to overheating – this can also be dangerous when it comes to electrical installations, especially if they’re in any way faulty.
  • Carbon compacting might also happen when you spray products with your extraction fan system turned on – whatever you spray ends up being pulled into the filter, which increases humidity and causes it to compact.
  • Carbon filters also have a shelf-life – make sure to check with the manufacturer to see how long your filter will last. Once it’s used up, any odors coming from your grow will simply pass through, unfiltered.
  • If you’re not planning on using your filter until your plants are in bloom or you’re simply done growing for now, you should clean the filter and the sock cover, then place the cover back on and cover it back up in its original packaging until you plan on using it again. If possible, pop in a couple of silicon sachets to keep humidity down. Keep it somewhere dry and dark and you should be able to keep it in perfect condition until you need it.
  • When buying your carbon filter make sure that is 1/4th stronger than your extractor in order to keep the air flow going perfectly; if not done right, you may end up slowing down the air flow in your extraction system which can cause some issues.

Using carbon filters is highly recommended when growing cannabis plants indoors. When installed properly they don’t tend to give many issues, but if you do run into a problem you can use this post to figure out what’s up. Get growing!

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