How to Control Odor in Your Grow Room

Part of the cannabis appeal is its distinct smell. 

Ah, that heavenly fragrance. 

Whether someone is smoking cannabis in the next room or growing in their balcony, we tend to get excited with a whiff of it, don't we?

Sure, the scent is instantly recognizable and remarkable too. Still, in some areas (or situations), it can cause a lot of trouble, especially if you don't want your neighbors (or cops) to know you are cultivating.

In that case, you can cover up or scrub the smell out of the air. 

But, you'll need to do a few things. Don't worry, we will tell you how. 

This guide is pretty long, so feel free to revisit and go through it. 

As you read on, we will show you the causes of the pungent smell and different ways you can scrub or cover it up in your grow room.

Causes of Grow Room Smell

Ask a non-smoker to describe the scent of cannabis. He'd probably say it's intense, skunky, or fruity. 

The plant's essential oils and terpenes are responsible for creating this distinct smell that's most potent when your plant is in the flowering phase of its growth. 

Sometimes, the smell is so strong it can be detected even a mile away!

This odor is a mixture of various chemicals that comprise multiple terpenes and terpenoids of your cannabis plant.

The terpenoids are classified into monoterpenoids, diterpenoids, triterpenoids, and sesquiterpenoids that are further divided into monocyclic, polycyclic, or acyclic hydrocarbons containing alcohols, ethers, ketones, aldehydes, or esters.

Additionally, each terpene gives it a distinct fragrance. For example, limonene gives it a citrus smell, camphene is woody, terpinolene is herbal, and carene is fir. 

But this is just scratching the surface. Cannabis plants have over 200 complex compounds that give them distinct odors.

Factors that Influence the Cannabis Odor

Cannabis gives off the odor throughout its growth cycle, not just during the flowering phase, but the level of smell constantly differs. The reason for this odor and its changes is partly due to your room's environment. Control these factors, and you can lower the odor emissions from your grow room.

Below are some of the primary factors that influence the aroma.

Grow Room Temperature

Temperature is perhaps the most significant contributor to cannabis smell since cannabis grows (and smells) better under the right conditions. 

While the temperatures dictate how well your cannabis grows, it can also dictate how it smells. 

For instance, if your grow room is too hot, the plant's essential oils evaporate quickly, leading to a more pungent odor. On the other hand, under the optimum temperatures of 21 to 27 degrees Celsius, your cannabis plant's scent won't be as strong.

But don't bring the temperatures too down as it may negatively affect the yield and quality.

Grow Room Humidity

Similarly, humidity is another factor that dictates how strong your cannabis smells. Higher humidity levels make the odor linger in the room for long. Thus, you must ensure the humidity in your grow room is always at proper levels, especially during the flowering phase when the plant produces more essential oils and terpenes.

Below is the ideal humidity levels for cannabis cultivation:

• Cloning or germinating stage: 70% to 80% RH
• Vegetative stage: 40% to 60% RH
• Flowering stage: 40% to 50% RH
• Final days of the flowering stage: < 40% RH

Airflow Direction and Volume

The rate and direction of airflow (or ventilation) is another factor that affects how strong your cannabis culture smells. 

For example, if your grow room lacks proper ventilation, then hot, stale air may get trapped in your room, making the scent stronger. Similarly, incorrect air direction may also cause the smell to get stronger. 

So, controlling the rate and flow of airflow within your grow room can significantly help you reduce or cover up the cannabis smell.

Type of Grow Lights Used

The grow light factor is interconnected to temperature — the larger the grow lights, the hotter the grow room, leading to a more pungent cannabis smell.

So, you can use 250W HID or LED light systems for a few plants as they don't get too hot. Note that HID lights tend to get really hot. The higher the wattage, the hotter they get, so ensure you get LEDs for bigger grow rooms. 

And if you are using ceramic metal halides, CFL, or high-power HID lights, ensure the lights are air-cooled to avoid frying your cannabis plants.

Ways to Control the Cannabis Odor

There are two ways you can control the cannabis odor: covering the smell up or scrubbing it entirely. Covering up the aroma essentially means hiding it by using another stronger smell, and scrubbing means eliminating the scent from the air completely.

And there are a few ways you can do so. So let's take a look at them.

Choose a Low Odor Strain to Avoid the Smell

Simple things first — grow a cannabis strain that inherently doesn't smell so strong since the strain significantly influences the odor. Different strains produce different terpenes and essential oils, giving the plants a unique fragrance, depending on their genetics.

Some of the best strains you can choose to make your odor-control labor easier include Durban Poison, Poison Express, Northern Lights, Polar Express, and Shark's Breath. In these, Durban Poison is famous for being almost odor-free. 

Install a Carbon Filter or Scrubber to Scrub the Smell

Installing a carbon filter is hands-down the most effective option for scrubbing the cannabis small. This device neutralizes any odors from the air passing through, and it also prevents any smell leaks through the windows or vents.

Carbon filters use activated carbon that absorbs the smell (along with other impurities) from the air to neutralize the smell. 

You must install the carbon filter in your ventilation system where the air is being pushed through the filter followed by the vent. The most common way is to set up the filter between the exhaust fan that pulls the air and the vents. 

Just ensure that the carbon filter is perfectly connected to the fan to provide the best performance. Here, the filter's spigot size must be the same as the fan's diameter. We don't recommend using a reducer between the fan and filter as it can impede efficiency, and if the filter is too small, it won't neutralize the smell properly.

For best results, we recommend using a carbon filter with a CFM rating of 300 to 400, a 400 CFM fan, and a couple of ducting hoses. A standard measurement of 15 cm for the filter, hose, and fan works well as it is adequate to pull the air out for most small-scale cannabis cultures.

Maintaining the carbon filter is also relatively easy. You have to replace the pre-filters every 3 to 6 months and the carbon filters every 9 to 18 months.

Using Carbon Filter with a Humidifier

If you are using a humidifier in your grow room, you must take extra precautions when using a carbon filter. First, avoid unfiltered water as it contains various minerals that can clog up the carbon filters. Instead, always use RO-purified water with the humidifier as it deionizes the water, making it safe for the carbon filter.

Installing a carbon filter — albeit expensive — is the most effective way to neutralize the cannabis smell in your grow room. It is easy to set up and maintain and lasts for years before breaking apart.

Use Odor Neutralizers to Cover Up the Smell

Odor neutralizers are another effective method of covering up the cannabis smell, but they don't eliminate the smell, only hide it. 

Unlike carbon scrubbers, neutralizers bind with the cannabis smell, and their strong fragrance hides the pungent smell.

Many cannabis growers use common odor neutralizers like bathroom sprays, candles, or incense sticks to hide the cannabis smell, but these methods aren't as effective, especially if you have large grow rooms. These household products don't produce a strong enough scent to hide the infamous odor of your plant. Plus, they can influence the natural flavor of your buds.

Instead, it would help if you used specific neutralizers designed to suppress the cannabis aroma. These neutralizers bind with the cannabis smell without overpowering the natural flavor of your buds. Plus, they are quite easy to use and cheap to buy. 

You can buy heavy-duty cannabis neutralizers from your local agrochemical stores for cheap! But remember to check the ingredients before buying — some components can still affect the buds' flavor.

Also, when choosing odor neutralizers, avoid chemical-based solutions. Instead, choose organic, biodegradable, skin-friendly, and non-carcinogenic solutions, so they are safe for your plant, the environment, and yourself.

These odors also need to be constant. Your cannabis plant will not stop smelling — it smells constantly, and the fragrance gets stronger as the plant grows. So, avoid using sprays inside the grow room. If anything, spraying outside the tent would work better. 

Instead, buy gel or mouthed jar neutralizers. You can leave them open in your room, and they will continuously neutralize the odor until they run out.

However, there is one caveat. We don't recommend using these products if your plant is in the flowering stage. This is because some heavy-duty, potent neutralizers emit a strong fragrance that can still affect your buds' flavor regardless of what their packaging claims. 

Set Up Negative Air Pressure 

If you have a greenhouse or a small grow room for cannabis, setting up negative air pressure would work perfectly. 

Essentially, setting up negative air pressure means controlling the input and output rate of the airflow in your room. Here, the input airflow must be lower than the output airflow. 

This creates a negative pressure within the grow room, ensuring that the only air flowing outside flows through the exhaust vent and no other holes like windows or doors. Plus, this keeps the grow room's air clean.

You can set up negative air pressure by using a powerful exhaust fan that pulls more air volume than the air entering the room through other channels like windows or doors. 

You can supplement the negative air pressure system with a carbon filter to neutralize the odor if you don't want your neighbors to know you are growing cannabis.

Note that negative air pressure to control the cannabis odor is only adequate with a small culture of a few plants. This is because more plants produce stronger aromas, and negative air pressure may not control it. 

Control the Heat and Humidity to Control Odor

Whatever other methods you use to scrub the odor, they won't be as effective if you don't control heat and humidity. 

When you are starting with the cultivation, you need to start with a humidity of around 70%. Then, you can gradually lower the humidity by 5% per week until the plant reaches its flowering stage. During the flowering stage, the humidity should be around 40%. 

As mentioned earlier, use humidifiers to stick to the recommended humidity levels for each stage. 

Similarly, it would help if you control the temperature, too. Maintain the ideal temperature between 21 to 27 degrees Celsius (69.8°F to 80.6°F) during the light cycle and 4 to 5 degrees lower during the dark hours. 

When your plant reaches the flowering stage, lower the temperature between 20 to 26 degrees Celsius (68°F to 78.8°F) since the plant smells the most during flowering. The plant smells too much during flowering because its oil and terpene production is at full force during these weeks.

Controlling the temperature and humidity won't only help reduce the odor, but it will also protect your plant from rot, mold, and fungus. 

Do note that different strains have varying tolerance to temperature and humidity levels. So, always source your cannabis seeds from reputable retailers who provide detailed descriptions and lab certificates. 

Also, participate in online growing forums to know more about your specific strain and what kind of atmosphere they perform their best in.

Temperature Control with High Powered Lights

Temperature is also influenced by the lights you use — high-powered lights heat a lot, increasing the room's temperature. 

So, if you are struggling to control your room's temperature, we recommend switching to LED lights from HID or CFL lights. HPS lights are also quite notorious for heating a lot. LED lights run cooler. 

And you can also direct intake fans towards the lights to cool them further down.

Odor Controlling Methods to Avoid: Word of Caution

The methods mentioned above work well, but various forums and the internet advise using air purifiers and ozone generators. We strongly recommend against these methods and here's why.

Ozone Generators are Bad for Your Health

Ozone generators are perhaps the worst method to control cannabis odor in your grow room. 

Most ozone generators claim to not only scrub the odor but also kill mold and mildew in your grow room, but they aren't effective at either. 

But that's not the reason why you should avoid ozone generators — we recommend not using them because they are dangerous to the environment and you.

In fact, they are deemed illegal in various parts of the world, like California. 

They can cause various lung problems, too. According to the EPA (US Environmental Protection Agency), ozone generators damage the lungs when inhaled.

And the American Lung Association classifies ozone as a lung irritant and claims that its excess exposure can cause various lung diseases like lung cancer. 

Even the OSHA (Occupational Safety and Health Administration) classifies ozone as a Major Indoor Air Contaminant.

For these reasons, you shouldn't use ozone generators to control your grow room's cannabis smell.

Air Filters or Purifiers Aren't Effective

On the other hand, we don't recommend using air filters because they aren't effective at controlling the pungent smell of cannabis in your grow room. 

You may find various air purifiers that claim to neutralize odors from the air, but it's all just a marketing tactic. In reality, these purifiers are inefficient at neutralizing even house odors, let alone the pungent aroma of cannabis. 

Instead, we recommend investing your money in a carbon filter as it is much more effective at scrubbing the pungent smell. 

Choosing the Best Method for Cannabis Odor Control

We have listed various methods you can choose (and two you must avoid) to control the cannabis odor in your grow room and around it. However, which one to choose is something that only you can decide.

As mentioned earlier, if you plan to start cultivating cannabis, you can start with a low-odor strain to reduce your overhead on controlling the odor. 

However, if you have already started growing cannabis but want to remove the smell altogether, you should invest in carbon filters. They are the best when it comes to scrubbing the smell entirely, especially if you don't want your neighbors to know you are growing cannabis.

And for smaller batches of cannabis, you can simply use heavy-duty odor neutralizers. They are cheap, easy to use, and don't require any kind of maintenance or effort. All you need to do is open and keep them in your grow room and forget about it.

Regardless of the three methods, we strongly recommend pairing them with negative air pressure and controlled heat and humidity. 

So, choose the one that suits you best and works for you.

Ways to Remove Odor from the Grow Room

While you set up methods to control cannabis odor in your grow room, you still need to remove the retained smell from your grow room. Simply airing out the room doesn't suffice. Here are a few tips on removing the aroma from your grow room completely to get a fresh start:

• Scrub the Rooms

Use cleaning solutions, like warm water, vinegar, and soap, to scrub your walls and remove the cannabis odor.

• Clean the Carpets

Next, clean the carpets by sprinkling baking soda on them. Leave the baking soda as it is for a day or two, and then use a vacuum cleaner to suck it from the carpets. You can even use some shampoo to clean them. 

• Clean the Furniture

To clean wooden furniture, wipe it down using a rag dipped in mild soap water. And use baking soda or fabric cleaners to clean fabric-lined furniture.

• Don't Ignore Tighter Spaces

The corners of your grow room may smell the most, so don't ignore them. Instead, run your vacuum cleaner through the tiny gaps and clean hard surfaces with a mild soap and water solution.

• Remove Odor from the Fabric

If the fabric in your grow room still smells like cannabis, you can use vinegar with hot water to re-clean them. Or wash them in your washing machine with mild soap.

As for other components of your grow room that may retain the cannabis smell, like the grow tent, for instance, follow the user manual instruction to clean them. 

Final Thoughts

It's true — cannabis has an unmistakable, distinct smell. But it is not pleasing for everyone. There are various reasons why you must control odor in your grow room, so it creates a safe environment for your plants, yourself, and your neighbors.

Below are some of the reasons why you must control the cannabis odor:

• To Avoid Legal Penalties

Even in regions where cannabis cultivation is legalized, many local municipalities have strict guidelines for cannabis grow rooms. For instance, some areas mandate zero odor emissions for cannabis cultivation.

You must control the scent if your region has such rules to avoid legal penalties.

• Neighborhood Complaints

On the other hand, the pungent cannabis smell can be annoying for your neighbors. In some cases, it can even give your neighbors headaches if you are growing multiple plants. Plus, there is still a stigma around cannabis that may cause problems for you.

So, controlling the pungent smell will keep your neighbor from getting annoyed or headaches and prevent extra hassles (or arguments).

• Evidence of Improper Setup

An underrated reason for odor control is that it can indicate an improper growing setup. For example, if your cannabis starts smelling too much, it may be a sign that your grow room has poor ventilation, high temperature or humidity levels, or low air circulation.

Use these tips to control odor in your grow room and stay safe!