Carbon Filter Outside Grow Tent- Guide & Warnings

Maybe, your grow tent isn’t ready to house a 16-pound carbon filter anyways. But you still want it to be there and filter the stinky smell away.

So, you’re thinking of putting the carbon filter outside grow tent.

Although, it might bring on a few consequences. But it’s still possible to keep carbon filter outside tent, and ventilate the air smell-free.  

In today’s post, we’ll tell you how. Stay tuned.  

Why Put The Carbon Filter Outside Tent?

First thing first, it’s not a recommended action at all. You should keep your carbon filter(and fan) inside the tent at first place.

But if you’ve got any situations like below, you might have to think otherwise-

Your grow tent size is too small

Usual carbon filters come with a 6” or 4” diameter along with a length of 16” to 24”. If your grow tent size is 10-30 square meter(2×4, 4×4, 4×8 etc.), you might face a hard time housing the filter.

Your tent might not be strong enough

Sometimes, you can not trust 100% on the strength of your grow tent. So, hanging a 16-20 pound carbon filter might get risky enough. And if it falls off from its place, it might cause a fire and ruin all the plants in a second.

You Don’t Want to Waste Grow Space

When the carbon filter is heavy or large enough not to be hung from the grow tent roof, many of us may think of keeping it on the floor. But that eats up quite of your grow space, which is an absolute premium. Also, this will draw warm air down to the plants, which is harmful for a good yield.

A better alternative to this plan, keeping the fan inside and the carbon filter outside of tent is the most desirable solution.

Items You Need

  1. The carbon filter.
  2. The inline fan.
  3. Inline fan silencer(for setup 2 only).
  4. Duct flanging kit. (To create air-tight holes on grow tent).
  5. Box cutter or wire cutter(to cut ducting).
  6. Ducting Clamps(to secure tight connections).  
  7. Duct tape(for extra secure seal).

Setting up the Carbon Filter Outside Grow Tent

At this step, we’ll go through steps of installing a carbon filter outside grow tent.

But before we begin, I think you should acknowledge something important!

Usually, carbon filters are likely to be the gateway to grow room ventilation system. So, the air first enters into the filter and gets free of smelly chemicals. A carbon filter is used as an exhaust filter, as it sucks air through it.

When you’re placing the filter outside, it’s not able to draw the air in such way anymore. Instead, air is blown into the filter, and it’s used as an intake filter.

However, taking that for granted, here are the two kinds of setups and the steps-

Setup Guide 1: Fan Inside- Filter Outside

In case 1, we’re supposed to keep the fan inside, and the filter outside.

In this case, your grow tent might not be strong or spacious enough to house the filter, but a fan is quite okay.

Now, here are the steps-

Step 1: Prepare the Carbon Filter

Take the filter out of the box and slide the pre-filter on it. There should be elastic bands with which you’ve to secure the placement of the pre-filter.

In many cases, growers prefer to place the pre-filter along with the inline fan intake port. If you think about what a pre-filter does, this might make sense.

Step 2: Find The Suitable Place for The Filter

As we’re thinking of placing the filter outside, the carbon filter placement should be as ‘close’ to the vent hole as possible.

The reason is, if it takes a good amount of ducting to reach the filter, the airflow will be hampered. As a consequence, the filtration of the carbon filter will be slowed down.

Step 3: Cut Ducting at the Required Length

Considering that you’ve installed the inline fan inside the tent, you’ve to connect it with the filter outside. Measure the length of the fan flange to the filter flange accurately. And cut exact length of ducting with a box cutter or wire cutter.

For precise and leak-free operation, it’s good to go with a duct flanging kit.

Step 4: Connect The Filter Flange with the Fan Flange

Now, attach the ducting with the tapered end of the fan, and take it outside through a vent hole.

Remember to keep the vent hole and the inline fan on the same line. This will decrease the loss of airflow towards the filter.

Finally, seal the vent hole, the fan-ducting joint and the filter-ducting joint with duct tapes and duct clamps.

Setup Guide 2: Both Fan and Filter are Outside

In some cases, growers would like to put both fan and the filter outside. Specially, when the fan-filter combo is supposed to keep as it is.

In such cases, you’ve to manage a way to reduce the enormous noise that inline fans make. Taken that for granted, here are the steps-

Step 1: Place the Carbon Filter Ready

Just like the first step of the previous setup, take the carbon filter out and put it on the place. Try to keep the filter as close as possible to the tent.

Step 2: Put the Fan on Top of the Filter

As we’re keeping both fan and the filter outside, we’ve to create a secure and air-tight fan-filter joint.

Put the tapered end of the fan on top of the filter. Now, secure the joint with 1-2 wraps of the foil duct tape. You might not get the duct tape along with the fan-filter combo. So, make sure to have one before you start the process.

Although it’s regular advice, make sure that the diameters of the fan and the filters are the same.

Step 3: Cut the Vent Hole and Ducting

At this point, create a hole on the tent wall if it doesn’t come with a built-in one. Use a duct flanging kit for accurate cut. Make sure to keep the diameter as same as the fan diameter.

Now, measure the distance from the vent hole to the fan, and cut a ducting of the length. As you know, you need to use a box cutter or wire cutter at this step.

Step 4: Secure Connections

Secure all of the connections with duct foil tape and duct clamps. The connections that should be under the rudder are- vent-ducting joint, ducting-fan joint and fan-filter joint.


  1. The fan might not draw enough air as it could do from inside.
  2. When the fan is outside, inline noise fan reduction will be extremely hard.

Consequences of Keeping The Filter Outside Tent

As we’ve told in the very beginning, putting the carbon filter outside isn’t a preferred method. It has a number of drawbacks, as long as you’re concerned about carbon filter 101.

At this point, we’re going to show you those consequences-

You’re Defeating The Purpose of the Pre-filter

Pre-filter is supposed to filter away large-in-size dust and debris inside grow tent. As you’re keeping the filter out, you’re defeating its purpose.

As a result, those dust and debris will enter into the fan directly. Which is an absolute ‘No-No’.

Remedy: Put the pre-filter on the opening of the vent hole(in case of ‘fan-filter combo outside’), or on the inline fan opening(in case of ‘fan inside, filter outside combo’.)  

You Can Not Draw Air Through The Filter Anymore

Although many manufacturers claim it, carbon filters are not equally efficient in pulling air inwards and outwards. In our case, we’re drawing it outwards. And that will cause a drop in the filter’s efficiency.

Also, this lack of efficiency may affect on the expected yield from your grow space.

Remedy: There’s no actual remedy of this. You’ve to deal with the issue in one way or another. But putting an oscilerating fan at the bottom might circulte the air and reduce the impact by some extent.    

The Fan has to Work Harder

No matter you keep the fan inside or outside the tent, it has to do extra work to push the exhaust air towards the filter. If there are a few turns in the ducting, the work might get even harder.

Remedy: Get a fan with at least 5-10% more CFM than what your grow system suggests. Also, keep the ducting as short and as straight as possible.

It Might Catch on A Fire

From the previous point, we can see that the fan has to go through a tremendous amount of stress while the filter/fan-filter combo is outside. The extra pressure on it may cause heat in the fan motor and may cause a failure.

In worst cases, it may lead to even fire.

Remedy: In this regard, we strongly recommend you to go for inline fans with circuit breaker assistance. If any extra stress or heat builds on the fan, it will automatically switch it off.

Here is our recommended speed controller & circuit breaker combo device-

Safety Concerns

Can i put carbon filter outside tent? Well, you might have got the answer with details instructions. Now, here are some safety tips that we want you to keep in mind-

  • Use Electric Fans with Circuit Breakers.
  • Keep The Ducting Short and Straight.
  • Put a pre-filter at any place to filter the air before entering into the ducting.
  • Use a fan with 5-10% more CFM than what the grow system requires.
  • Make sure to use an electric inline fan with a circuit breaker.

We will be happy to hear your thoughts

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