5 Steps To Place The Carbon Filter Outside Of Grow Tent

The carbon filter is one of the most critical building blocks in your grow tent. It captures and eliminates stinky smells which are produced by your plants in isolation that might spread throughout your house.

A lot of indoor gardening enthusiasts are favoring the placement of the carbon filter outside of their grow tent for various reasons.

In this article, we will discuss the 5 steps you should follow to place the carbon filter outside of a grow tent and what are the risks that might arise from doing so.

Why Place The Carbon Filter Outside?

Many indoor gardeners prefer to place their carbon filters outside of their grow tents instead of inside. This is because there are a few distinct advantages that can be gained by placing the filter outside of the tent.

Saving Up Grow Tent Space

One of the main reasons why many indoor gardeners prefer to place their carbon filters outside of their grow tents instead of inside is to save up space.

On average, a carbon filter will occupy up to 16% of the total grow tent internal area.

Space inside a grow tent is an extremely valuable asset. Carbon filters do occupy a lot of space when placed inside.

This saved-up space could be used to add another rack that can carry extra plant pots.

Higher Carbon Filter Size

A great way to make sure that smell will not leak outside of the grow tent and spread throughout your house is to get a carbon filter with a larger size than that required for your grow tent.

Some growers set up an 8″ carbon filter to a 2×2 grow tent in order to eliminate smell as much as possible. If this carbon filter is placed inside it would take almost a quarter of the grow tent’s internal area. So, growers tend to place the carbon filter outside.

To find out more about how much is it going to cost in order for you to smell-proof your grow tent, check this article that I wrote including a detailed cost breakdown.

Grow Tent Might Not Hold On Weight

Many people tend to place the filter outside because they doubt whether the grow tent will be strong enough to hold the weight or not.

Grow tents can hold an average weight of 150 lbs when distributed correctly on a strong metal frame.

The exact weight a grow tent can hold varies by every brand. This is why I have created this guide for every grower to know the actual weight capacity of every grow tent brand on the market.

Placing Carbon Filter Inside VS Outside Grow Tent

In the table below I will show you a brief comparison between placing the carbon filter inside vs outside t

Point Of ComparisonInsideOutside
Efficiency Higher Efficiency Lower Efficiency
Convenience More Convenient Less Convenient
SpaceOccupy More Internal SpaceNo Internal Space Occupation
RisksFewer Risks More Risks Involved
Carbon Filter Inside VS Outside Grow Tent


The efficiency of the carbon filter is significantly reduced when placing the carbon filter outside the grow tent. Carbon filters are designed to suck air. So, pushing air through it will not provide you with the maximum odor elimination efficiency.

I reviewed the efficiency of the best-selling carbon filter brands in this article, go check it out.


Carbon filters are designed to be placed inside a grow tent. When placing the carbon filter outside, it will require a lot of tools and ducting that might be a hassle for some growers. On the other hand, putting the carbon filter where it is designed to be will require minimum to no extra tools and procedures.


As I have mentioned before, the whole reason why many growers did choose to put their carbon filter outside is to save up some extra space. This extra space could be used productively in growing more plants thus increasing your final yield.

Risks Involved

There are almost no risks involved in placing your carbon filter inside.

On the other hand, if you place your carbon filter outside, you have to understand that there are a few risk factors involved.

Your exhaust fan motor will eventually fail due to significantly increasing the force applied to it. It takes much more energy to blow air into a filter than to suck air through the filter.

If the carbon filter is not fixed properly outside, it might fall and cause a significant fire hazard.

How To Place The Carbon Filter Outside Of Grow Tent

Here comes the step-by-step guide that you will need to follow in order to place the carbon filter outside the grow tent.

Step 1: Get The Carbon Filter Ready for Use

Retrieve the filter from the box. Remove any packing stuffing from around the filter and make sure it is ready for use

Place the pre-filter in its proper position. In any normal carbon filter setting, the prefilter is placed over the external surface of the filter. In this situation, we are going to place the pre-filter in the hollow space on the inside of the filter.

Step 2: Locate An Appropriate Spot For The Filter

When we are choosing the appropriate spot for the filter, there is a general rule which is, it needs to be as near as possible to the exhaust fan.

Placing the carbon filter away from the exhaust fan will require a lot of ducting lengths. This will increase the amount of force required by the exhaust fan to blow air until it reaches the carbon filter.

Step 3: Cut Ducting To The Desired Size

In order to connect the inline fan that you’ve installed in your tent to the filter outside, you must measure the length between the fan flange and the filter flange accurately. Then, use a box cutter to cut the ducting to the exact length that is needed.

It is preferred for the ducting to be made of PVC for better durability.

You can use a duct reducer or increase it to compensate for any discrepancies in the duct sizes and carbon filter size.

Step 4: Joining The Filter Flange With The Fan Flange

Connect both the filter flange and the fan flange with each other through the PVC duct that you have cut in step 3.

To secure and seal all the flanges and the ducts together, use heavy-duty duct tape.

Step 5: Run Seal And Efficiency Test

To test the seal and efficiency of your carbon filter setup, there is no better way than running a smoke test.

Simply place a burning piece of paper near the exhaust fan inside the grow tent. The smoke will get sucked by the exhaust fan and will blow through the carbon filter setup.

Inspect if there is any smoke leakage from the carbon filter setup through any of the ducts or flanges.

Finally, check if the exhaust air is still carrying a smokey smell from the inside or if it has been absorbed by the carbon filter.

This smoke test was used in testing the efficiency of a DIY carbon filter, and I am sure it is critical when trying to test the efficiency of any carbon filter

Can You Push Air Into Carbon Filter?

Carbon filters are designed to pull air by negative pressure through the pre-filter for larger debris and then air pass through the carbon bed for odor. However, it is possible to push air through the filter as well, although it is recommended that the outer filter be taken off for this purpose in order to maximize filtration efficiency.

On the other side, if you want to maximize the odor absorption properties of the carbon filter, you must follow the manufacturer’s instructions.


Placing your carbon filter outside of the grow tent is a method that will save you a lot of space which can be utilized in growing and producing more yield. However, you need to understand the risks that will come while following this method. Moreover, you need to follow the steps mentioned in order to get the best possible carbon filter setup.

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts