5 Ways to Control Odors in a Growroom

By Rich Hamilton
Published: April 27, 2021 | Last updated: May 25, 2021 09:10:46
Key Takeaways

Growers love the smell of their cannabis plants, but many people don’t take kindly to the pungent, skunky fragrance. Rich Hamilton shares some great ideas on how to control the smell wafting from your growroom.

To get their aroma, cannabis plants release volatile organic compounds (VOCs) into the air. The problem is these VOCs can create quite strong, pungent smells that can be tell-tale signs of what you are growing, which you may not necessarily want everyone being aware of.

The good news, however, is these smells can be removed, reduced, and prevented easily, with a little know-how. Here are all the tricks and methods you need to know to keep those funky smells at bay.


Carbon Filters / Carbon Scrubbers

By far the best way to get rid of growroom odor is with a carbon filter. They literally scrub plant smells out of the air before the air is extracted from the growroom.

Carbon filters are an essential part of your ventilation system. The extractor fan pulls air from your growroom through a filter containing an activated layer of carbon. As this happens, the odor released by your plants is trapped and retained inside the pores of the activated carbon.

There are many carbon filters available out there, and to make sure you are purchasing a quality one you should look out for a deep carbon bed, as the deeper the carbon bed, the more activated carbon there will be. This means the filter can remove more odor and will have a longer overall life span.


Carbon filter inside a grow tent.Carbon filters will successfully prevent the plant’s aroma from leaking out of the grow room.

To make sure your fan and filter are perfectly connected, your spigot size needs to match the diameter of your fan. If this is not the case then you can use a reducer, however, this will impede the efficiency of your fan and filter. If your carbon filter spigot is too small, it will not be suitable for the level of odor you need to scrub as the air needs to be in contact with the carbon in your filter long enough to remove the odors.

To keep your carbon filter working as efficiently as possible you should make sure you maintain it properly. Replace pre-filters every three to six months. Pre-filters and filter sleeves are preventative measures to stop dust and debris from getting into your carbon filter, which could reduce the life of your carbon. Replace carbon filters every nine months to two years, or whenever you think they are needed. This will depend on which filter you buy. Check the care instructions for specific guidelines.

Do not use a humidifier in your growroom with unfiltered water. Unfiltered water contains minerals that, when used in a humidifier, can clog up carbon filters and reduce their life. To prevent this, you should always use RO (reverse osmosis) water with your humidifiers. Reverse osmosis is a process where you demineralize or deionize water by pushing it under pressure through a semi-permeable membrane.

Negative Pressure

Negative pressure is the best pressure for a growroom. This means there is more air leaving the growroom than there is being drawn in. The benefits of negative pressure are that temperature and humidity are easier to control and growroom odor is reduced.

To maintain negative pressure you should use a less powerful intake fan so that you are drawing in 20 percent less air than you are extracting, otherwise your tent can become too full of smelly, unfiltered air which can then start seeping out of zippers and seams before it passes through your carbon filter.


Ozone Generators

Ozone generators remove odors rather than covering them up. They do this via oxidation. Ozone is three oxygen atoms (O3) bonded together. It’s like the oxygen we breathe with an extra oxygen atom. Oxygen atoms usually exist in bonded pairs. So, the extra oxygen atom in O3 is very unstable, breaking off and binding to organic molecules such as the volatile organic compounds (VOCs) that cause plant smells. When this happens, any odors are oxidized and eliminated.

There are several different types of ozone generators. Inline generators are used within your ventilation system and alongside your carbon filter. They act as an extra layer to ensure all odors are removed before the air is extracted.

Standalone generators can be plugged into the mains and emit small amounts of ozone directly into your growroom to destroy odors while still in your growing environment.

(Read also: The Latest Automation Options for Cannabis Cultivation)


Ozone generators are the subject of much debate, and opinions on whether you should or should not use them are very split. It is generally advised that if you do use an ozone generator, then it should not be used outside of the growroom, especially in a domestic environment as they can pose some health risks.

Some people are more susceptible than others to ozone and may be more likely to experience adverse health effects. People at particular risk are children, the elderly, and people with asthma.

Exposure to ozone can cause eye, nose, throat and lung irritation, coughing and shortness of breath, and may exacerbate chronic respiratory diseases such as asthma. Excessive use can also adversely damage materials such as rubber, electrical wire coatings, and fabrics.

It’s also advisable to switch off any ozone generator if you plan on working in your growroom for an extended period.

Cannabis plant in the flowering stage.Cannabis plants smell the strongest during their flowering stage.

Odor Neutralizers: Blocks and Sprays

These are the best and safest neutralizers to use outside your growing area for keeping peace of mind over any smells you think may still make it out of your growroom. Odor neutralizers are for use outside of the growroom only, as they are so effective, they can impact the final smell and taste of your harvested product. You can, however, get blocks that sit in your extra line ducting. This is okay as they are only neutralizing the air that has already left the main chamber of your growroom and is on the way to being extracted.

The sprays are great for eliminating odors that may cling to your clothes after you have left the growroom.

Odor neutralizers work in several ways where the VOC molecules released from the plants either are attracted to, enter and bond with the neutralizer’s active ingredients, or are absorbed and held on the surface of the neutralizer’s molecules. Also, they can be permanently bonded by chemical reaction to the neutralizer’s ingredients and permanently cancelled out and destroyed.

Controlling Heat and Humidity in Flowering

Your cannabis plants are at their smelliest during flowering. Firstly, because this is when the buds are ripening, and all the oils and terpenes are at their highest levels. Secondly, the increase in heat and possible humidity during flower will emphasize this even more. Your humidity level should be kept low during flowering anyway in order to avoid rot, fungus, and mold, but this is another reason to keep it low as smells intensify under humid conditions. Air circulation fans will also help prevent hot, humid spots around your plants.

(Read also: Managing Cannabis Fan Leaves)

If you are struggling to control temperature, which is adversely increasing humidity, then you could try switching to LED lights or try cooling your lights by pushing air from outside the tent over them. You can push air from inside the growroom over your lights, but this is not a great idea as the air from inside your tent is smelly and full of plant debris that will dirty your reflectors and impede your light’s performance.


It’s true that one of the most appealing characteristics of cannabis, to both the grower and the end user, is its pungent, unique smell.

Unfortunately, that same smell is what makes it so instantly recognizable and can cause so many headaches for growers in the process of raising a crop. For this reason, it is imperative to make that smell a non-issue.

As we have seen here, however, there are a few good options out there to stop these tell-tale signs from escaping your growroom. By either scrubbing the smell from of the air or finding a way to cover it up.

All these tips are good to know, as for a small grow with just one or two plants, you will usually get away with covering up the smell, but for a larger grow, you need to know how to scrub the air to make sure you’re not leaking any smells that might catch the attention of people who don’t want to smell cannabis. When growing, it is always best to be mindful of other people around your facility, however small or large that facility is.

Master the art of odor control competently and you will be able to focus all your attention on getting the most out of your plants and raising the best crop you can with total peace of mind.

(Read next: The Benefits of Adding CO2 During the Cloning Stage)


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Written by Rich Hamilton | Writer, Consultant, Author of The Growers Guide

Profile Picture of Rich Hamilton

Rich Hamilton has been in the hydroponics industry for more than 20 years, working originally as a general manager in a hydroponics retail outlet before becoming an account manager at Century Growsystems. He enjoys working on a daily basis with shop owners, manufacturers, distributors, and end users to develop premium products.

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