How Often Should I Change/Replace Carbon Filter in Grow Room?

Grow tent becomes such a source of annoyance when it starts to push the plant-smells outside. You might use a carbon filter for that, but sometimes it can get saturated and you need to change the activated carbon, or the entire filter itself.

In a broad sense, carbon filters are needed to be changed after 18-24 months of regular(24/7) use. In less demanding situations, they can last up to 4 years. However, this lifetime depends on the carbon quality, usage, humidity, plant types etc.

By the way, that was just the summary of what we’ve to tell you about carbon filter change frequency in grow tent. We’ve crafted an entire post breaking down things into bite-size chunks.

Take a break from whatever you’re doing, and let’s dive in-

How Grow Carbon Filters work?

I know, you’ve not come here to read about how carbon filters work. But before we dive deep into the discussion on ‘When to change carbon filter grow tent?’, you should understand the way a carbon filter loses its workability.

Carbon filters are full of activated carbon(charcoal), and they are full of pores. The organic particles that contain the smell of grow plants are attracted to these carbons while passing through the filter.

So, the particles get bound onto those pores, and no smell can go out and hit the receptors in your nose.

Now, these spots where the organic particles are trapped on, are called binding sites. And it’s limited in amount in carbon filter. The amount depends on the size of the filter, the mass of the activated carbon, and the particle size of the charcoal as well.

Anyway, whenever the binding sites are not available anymore, it demands a new set of activated carbon.

How to Recognize the Time To Change The Filter?

Obviously, when your carbon filter will be out of order, it won’t be able to trap the smelly particles anymore. So smells will come out and let everyone know about this ‘hobby’ of yours.

But what if your nose can’t recognize the moment when it happens? You know, the olfactory receptors of yours are pretty used to the smell. So it can’t recognize the sudden presence of it.

So, is there any other way to recognize how often to change carbon filter in grow tent?

Yeah, there are two ways actually.

#1- Smell the Active Carbon

Remember the sweet carbon smell when the filter was new? Well, that smell is an indicator of how much alive the activated carbon is. After every 3-4 months(or whenever you feel like), seek for that smell in the carbon filter. The moment you won’t sense it anymore is the moment when the activated charcoals need to be replaced.

#2- Let Someone Trustworthy Smell It

Another alternative way is, let someone else check for the smell outside grow tent. The person should be someone who doesn’t live around, and someone who’s not used to the smell of your grow plants.

Either way, you should have a firm idea on the carbon filter change frequency.

How Long Does a Carbon Filter Last in A Grow Room?

First thing first, the entire carbon filter never goes out of order, only the activated charcoal does.

However, usually activated charcoals last for around 24 months of regular use. But we have seen people use a carbon filter for 10 years with just one refill. On the other hand, sometimes, it needs to be replaced once in a year.

In case you’re looking forward for changing frequency of a air filters of other types, here is a quick roundup-

Table: Air Filter Changing Frequency for Different Types

Types of air filtersLifetime/Changing Frequency
UV Lamps or Bulbs12 Months
Pre & Post Filters6 – 8 Months
Carbon Foam Filter10 – 12 Months
Activated Carbon Filter2 – 4 Years
Non-sealed HEPA Filter6 – 12 Months
Sealed HEPA Filter(True)2 – 5 Years

5 Deciding Factors of Carbon Filter Change Frequency

Moving on to carbon filter durability, there are a number of deciding factors. To understand the reasons on which this lifetime depends, here is the detailed discussion-

1. What Type of Carbon Particles You Have?

The lifespan of a carbon filter mostly depends on the carbon quality. You might see carbon everywhere around, but not all of them are up to the par to be chemically activated and used in smell filtration.

There are two types of carbons used in filters- the Granulated Carbon and the Pelletized carbons.

Granular activated carbon vs pelletized activated carbon
Image: Two types of activated carbon

Granulated carbons are likely to provide the best carbon filter durability, as there is more surface to catch up with the particles. They are light in density, and therefore, have more surface area per gram.

Pelletized carbons are regularly and uniformly shaped particles that have fewer pores and contact time with smelly chemicals. Usually, they are denser and heavier than granulated carbon. And filters filled up with this won’t have a long lifetime.

2. What’s the Density of Carbon?

Next to the ‘size’, density is another physical property of activated carbons. There are dense carbons of 50 to 60 grams/cubic cm, and there are lighter carbons of 30-40 grams/cubic cc.

Denser carbons are likely to have pores of 2 to 25 nanometers in size. Which turns the whole carbon bed ‘not too spacious’ for the particles. Result? They cause premature clogging and lessens the life of the filter.

On the other hand, lightly dense carbons have wider pore structures. They allow both large and small particles to roam around the pores and get trapped onto them. So, they last for a longer lifespan.

3. How Humid The Environment Is?

There is a direct connection between the relative humidity of the grow room and the activeness of the filter. If the relative humidity goes over 85%, the activated carbons will almost stop working.

Make sure you keep the growing environment dry and keep the humidity under 60-70%. You might consider using a dehumidifier on that purpose.

4. Reversible or Irreversible?

We can split carbon filters into two kinds- Reversible(ones that are inline), and Irreversible(ones with a dead end).

As the name suggests, reversible filters can be turned around and flip the ‘intake’ and ‘exhaust’ openings. This will certainly give you a few months of extra lifetime. But a drawback is, you can’t do that for more than once or twice.

On the other hand, there are irreversible filters which have only intake and to exhaust port. So you’re done with the existing carbon bed once it’s saturated at on the intake side.

But they are pretty handy when carbon filter placement is at the beginning of the vent line, or outside grow room.  

5. How Aromatic The Plants Are?

As a matter of fact, more aromatic plants pushes more smelly compounds through the filter. If you’ve such plants in the tent, your carbon filter would ask for a refill pretty frequently.

No wonder in that, right?

Pro Tips to Boost Carbon Filter Lifetime

You definitely would like your carbon filter to last for longer, right? Consider these following actionables to get surprising results-

Get A1-graded Australian Certified Virgin Charcoal

If you want your carbon air filter to last for at least a few years, there should be no compromise with the quality of the carbon granules used in them.

Among all kind of activated carbon beds, Australian certified activated carbon is recognized as the best quality. There are RC-412, RC-48 grade activated carbon etc, which are recognized as the best quality activated charcoal beds for carbon air filters.

Quick Pick:

RC-412: iPower 4” RC-412 grade activated carbon filter

RC-48: Phresh Filter RC-48 grade activated carbon filter

Keep The Humidity Under Control

To let the activated carbon function properly, it’s mandatory to keep the humidity under control. The threshold limit is to keep the relative humidity under 85%. But we recommend you to stick to even lower level of humidity, based on the stage your plants are in.

  • Clones stage: 60% to 80% RH
  • Vegitative stage: 50% to 60% RH
  • Flowering stage: 40% to 60% RH
  • Late flower/cropping: 40% to 50% RH

To control the humidity, it’s obvious to use a dedicated dehumidifier. Besides, there are other ways to keep it under control. Keeping the airflow right, using water lines etc. are some tips we can recommend.

Quick Pick:

Frigidaire FAD504DWD 50-Pint Dehumidifier

Always, Always Use A Pre-filter

No matter you keep the carbon filter inside or outside the tent, make sure there is always a pre-filter to keep the larger dust away from the carbon bed.

What if the filter is outside? It doesn’t make putting the pre-filter on, right?

Yeah, that’s a valid question. But when you’re drawing air through the filter by putting it at the end of your ventilation system, you can put the pre-filter inside instead of outside.

Here is a picture-

carbon pre-filter inside the filter

On an additional point, clean and wash your pre-filter to keep it up for work efficiently. You can wash them in washing machines. In case you badly need a new one, here’s the quick pick-

Quick Pick-

6” Filter Compatible: iPower 6 Inch Replacement Pre-Filter

4” Filter Compatible: iPower 4 Inch Replacement Pre-Filter

Use An Ozone Generator

The question might raise an eyebrow of yours in the first place. But this is indeed an important consideration.

When the filter is the start-point of your ventilation system, raw air with pollutants will directly enter. Yeah, we know the pre-filter is there. But yet, there are compound particles inside the air that the pre-filter cannot ‘filter’.

To make the smelly compounds more ‘absorbable’ for the filter, use an ozone generator. It will greatly boost the lifetime of the filter as well.   

Keep in mind that, it can be banned in some states like California.

Quick Pick:

Uvonair 8 Inch CD-In-Line Duct Ozonator

Keep the Body Material In Mind

In the discussion of carbon filter durability, most of us are concerned about the activated carbon bed only. But The ‘body’ of the filter and its durability should be on the list as well.

Usually, we get to see filters made of aluminum and galvanized steel. Although aluminum-made filters come at a cheaper price. But for the long course, galvanized steel filters will give you more efficiency, more durability, and more open area for air transfer.

Quick Pick:

Amagabeli 4 inch Carbon Filter

Closing Words

Well, that’s the dead end of the article. Hope you’ve learned the correct carbon filter replacement frequency in grow room, and how often should I change my carbon filter in grow room.

Happy gardening!

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