How to build a carbon filter grow room

Published Apr 2, 2019 09:30 a.m. ET

With cannabis now legal to grow in much of the western world, there are a significant number of people who are considering the possibility of having their own personal grow room. With so many different options to choose from including light fixtures, grow tents and substrate mixes it can be easy to feel a bit confused. The choices that you make will greatly impact the overall production of your cannabis plants, but some of the most recommended additions can come at a considerable expense. One of the few things that you can depend on no matter which method you want to use to grow cannabis is that both you and your grow room will benefit greatly from the addition of a carbon filter.

What is a carbon filter?

A carbon filter is a filtration system that relies on chemistry and placement to filter the air from your grow room outside. The carbon that is used to make the lining of a carbon filter is active, which creates a unique platform that will hold onto smells while allowing fresh air to flow freely. Carbon filters can last long term anywhere from 6 months to 1 year but do require replacing after consistent use and more often if used in a large space. They can be used to filter entire rooms or affixed to grow tents to maintain a smell free air flow from the environment inside.

Best carbon filter for grow room

The best carbon filter for your grow room will depend on the cubic feet of the growing area. The size and kind will depend that you need will depend on the exhaust fan you use, as it will need to attach to a working exhaust to function. A carbon filter does not have any force or moving parts on its own and relies on the blades of the exhaust fan to create the airflow through it. Your filter will need to be thick enough to support the size of the room, and wide enough to line up with the diameter of your exhaust. The one general rule to choosing a carbon filter is selecting one that has a lower CFM (cubic feet per meter) then your fan. If you don’t, then you could risk burning the exhaust fan out which can create a potential fire hazard. If you have the option between a charcoal filter and an activated carbon filter, you may want to go for the activated carbon filter. The names of these two filters are used interchangeably though chances are if you have the option, the later maybe better suited to your needs.

Carbon filter on grow tents

Carbon filters for marijuana grow tents are amazingly effective as the size of the space is so small and well-sealed that it doesn’t require a large exhaust fan. This is the most efficient way to build a carbon grow room. If you are using a grow tent that comes pre-equipped with a fan, then your job will be cheap and straightforward, since you will only have to buy a filter that is an adequate size. If you are starting from scratch with just a grow tent, then things can get a bit more complicated. Some will have pre-cut holes for you to install an exhaust system, and many brands will even offer models that are made specifically to work with their products. In the end, it doesn’t matter which kind of exhaust you buy, if it is strong enough to create a vacuum inside of the grow room.

  1. Once you have it in place, you can arrange the smell removing the filter. Line up the edges of the exhaust fan and the carbon filter and slide one into the other. If there is an air gap that will need to be sealed. Electrical or duct tape can be used to make sure there are no leaks in your system.

  2. When you have it in place, and it’s fully attached, you are good to go. Turn on the exhaust and your carbon filter will immediately begin filtering out any air that is forced outside of the grow tent.

Carbon filter grow room


Carbon filter grow rooms are the same only on a slightly larger scale. Though trying to filter the smell from an entire room is much more difficult to achieve than a tiny grow tent, often this is the setup that requires them most. When the old air runs through the exhaust system in your grow room, it usually ends up outside. This can upset neighbors and pedestrians, especially if you live in a city where there isn’t always a whole lot of breathing room. The addition of a carbon filter can change all of that if you have the correct size and ensure the best air seal possible. Now, we are going to assume you are starting with a grow room that has no exhaust system to explain how the setup of an efficient carbon grow-room should be planned out. You will need either a window or the ability to create a hole for the exhaust to be installed.

  1. The very first step will be to assess the overall seal of the room. Look for windows, doors, and any other ways that air manages to flow either through the house or outside. All these weaknesses need to be addressed for an exhaust system to work properly. To do this try to seal up any openings that you can. Window cling over windows and even some closet doors can be a fast way to get the job done. You will need a window slightly open to install an exhaust which can be carved out afterward.

  2. Now you will need an exhaust system that can sufficiently provide airflow for the size of your grow room at least once every two or three minutes. To do that you will need to calculate the CFM of your room. First measure the rooms length, height, and width. Now multiply all three numbers together to get the results. For example, if your space is 6 feet by 6 feet by 10 feet than multiply 6x6x10. Once you have that total, you will take that answer and divide it by 3 to get the proper CFM measurement of the space.

  3. This is one of the essential steps of building an efficient carbon grow room. The exhaust is the driving force that will draw the air through the carbon filter. The goal is to get one that is large enough for the room without going so big that it’s an unnecessary drain on hydro. The other aspect to consider is how easy it will be to set up. Some come equipped with window holders that can make things a little easier to install.

  4. An exhaust system will need to be installed either in a window or through a hole of some sort in the wall. Here we will assume that you have a window exhaust system that has a piece that acts as a wall to support it. Follow the instructions for the installation of the hardware and affix the exhaust.

  5. Now that you have likely broken one of your seals and even created new pathways for air to escape, you will need to do a second seal check on everything. Duct tape, window wrap, and electric tape are excellent for closing up small space that might let air that hasn’t been filtered yet escape.

  6. Once finished you should have a well-sealed exhaust system. To double check, you should flip it on while standing inside. If it is sealed properly, you should feel the vacuum that is created. If you don’t than seal check once more, but some spaces are impossible to close off entirely so just do the best that you can.

  7. We are finally at the part where you will install the carbon filter for your grow room. Carbon filters are designed in a way that can be used with any air intake system; the goal is to choose one that fits the circumference of the fan as it makes it easier to seal and sturdier. You will also need to pick one that has an equal or lower CFM than the exhaust system. Once you have it the actual installation is relatively easy. Most will come with a wall bracket to hang off. That will support most of the weight of the filter while the seal that is created after you press the ends into each other and tape them will help as well. Just like before you don’t want any air from the room to be able to get around the carbon filter.

  8. Now that you have the perfect air intake and carbon filter system it is time to put it to the test. Flip the exhaust fan on and feel the difference in air quality. Your plants will love you for it.



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