Products and Methods for Reducing Marijuana Grow Room Odors

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The term “dank” is typically used to describe the distinct heavy odor of marijuana. At the same time, it also refers to high-quality weed. The coincidence makes perfect sense since cannabis is not only enjoyed for its effects but also for its complex aromas and flavors that contribute to its therapeutic value.

Odoriferous marijuana is fine and good, if it’s not illegal where you are. But in most cases, you want to get rid of this unmistakable smell since it can get you into trouble. 

Marijuana is smelly

Having a bit of understanding why your cannabis plants are stinky can give you a good idea on how you can deal with its smell.

The smell of cannabis comes from its terpenes and terpenoids. Each strain will have its own smell but in general, the pungent scent comes from varying levels of the following:

  • Camphene
  • Carene
  • Caryophyllene
  • Geraniol
  • Humulene
  • Limonene
  • Linalool
  • Myrcene
  • Phellandrene
  • Pinene
  • Pulegone
  • Sabinene
  • Terpineol
  • Terpinolene

Your plants will start to smell at around 3 to 6 weeks. It will get stronger once the flowers come out. Bigger plants tend to smell more but some strains emit more odor than others.

To cover or to scrub?

If you are a new home grower who’s wondering if it’s possible to cover up the smell of your grow room instead of scrubbing it, the answer is: you shouldn’t. Don’t be tempted to cut costs by not installing a proper ventilation and filtration system, it is an absolute must for any home growing setup for the following reasons:

  • Your plants need fresh air – Proper air circulation in an indoor setup is critical since cannabis plants need around 1,000-1,400 parts per million (ppm) of carbon dioxide to grow well. Airflow also gets rid of the moisture produced through respiration which can cause bud rot, mold or mildew if allowed to build up. Stale air is also a magnet for pests like spider mites. However, once the odorous air has been moved out, you can’t expect the smell to dissipate within the room or even outdoors which is why it has to be eliminated through a filter.
  • Other odors can change the smell of your weed – Any strong odors that get within the vicinity of your marijuana plants will stick to it, which is one of the reasons why most home growers use grow tents to create an isolated environment for their plants. This means introducing other odors to mask the skunk of your plants is absolutely not an option. 

Best method for reducing marijuana grow room odors

Let’s get this out of the way: the best and only recommended method of dealing with marijuana odors in an indoor growing setup is by installing a proper air filtration system which typically consists of the following parts:

Duct – This is any kind of tube where the filtered air is expelled. Sometimes intake ducts are also needed for some setups. Flexible aluminum foil duct hoses are the most popular choice for most home growers.

Exhaust fan – This is a specialized fan that sucks air into the filter and exhaust duct hose. 

Filter – It’s difficult to find anything better than a carbon filter for removing grow room smells. Activated charcoal, which is highly adsorptive, is used in such filters to capture terpenes and other pungent molecules before the air gets vented outside. The cylindrical filters that you often see on the market are carbon filters that already packaged in a silencer or muffler.

How to choose your carbon filter exhaust system

To know the specs of the carbon filter system that you need to get, you first have to determine the air filtration requirements of your grow room. You get this by computing for its CFM (cubic feet per minute) which is a value that represents the amount of ventilation your grow space needs per minute. The kind of carbon filter, duct, and silencer that you use, how they are installed, as well as the amount of heat generated by your grow lights will add to this number. The total required CFM will then give you an idea of how powerful your intake and inline fans need to be for ventilation to be enough.

In most cases, you can get by with a 4-inch carbon filter if you have a 4×4 tent. This costs somewhere around $30 to $50 with replacement filters costing $10-$15 on average. But if you are using HID lights, you may want to use a 6-inch filter with a more powerful fan.

If computing for CFM to determine carbon filter sizes and fan power ratings seems complicated, relax. In most cases, you won’t even need to bother matching parts since you can buy grow tents that come with their own carbon filter system. Likewise, you’ll also find matching fans and carbon filters being sold together as kits.

Cut costs, make your own!

Good news is, if you have some materials lying around, you can even build your own. The basic idea is just to create a vacuum in your grow room so that the odor-laden air can be sucked by a fan into a filter filled with activated charcoal pellets. Here’s a good tutorial that can show you how to build one. 

Carbon filters, even the DIY ones, should last you around a year or longer. However, an increase in smell is always a good sign that it’s time to replace your filter.

Alternative methods for reducing marijuana odors

Carbon filter exhaust systems are now relatively inexpensive and if you’re serious with growing marijuana at home, there’s really no excuse not to get one. But if you’re looking for a temporary fix for some reason, here are a few alternatives you can look into:

Air purifiers

Price range: Around $38 (JINPUS Air Purifier Small Air Cleaner for Home with HEPA Filter) up to $513 (Coway Airmega 400 Smart Air Purifier with 1,560 sq. ft. Coverage)


  • Also filters airborne diseases and microorganisms


  • Not as efficient as a carbon filter
  • Can even be more expensive than a carbon filter system

You can use your air purifier as a temporary fix, but it is not worth buying one solely for the purpose of reducing odors in your growing room. In some setups, especially those where there is a lot of risk for airborne diseases, an air purifier like Airo Home can be useful, but if you can spend for one, then you can certainly spend for a proper carbon filter system.

Odor neutralizers

Price range: Around $16 (EnviroSupply 4mm Pellet Activated Carbon (Virgin Bituminous Coal) to $52 (Ona Gel Pro, 1 Gallon Jar)


  • Effective in binding odorous molecules
  • Cheap


  • Some products don’t have a neutral scent which can affect your plant’s smell and flavor
  • Does not help in proper ventilation and air circulation

Here are some better options to use if you don’t have a proper exhaust filter system installed yet. Like activated charcoal, these products are made of material that effectively bind odor molecules. However, be careful when placing stronger products like ONA as it can affect the smell of your plants. Your best bet when using these would be to blow the smelly air away from the grow space to these products.

  • Activated charcoal – Typically made out of coconut shell or bamboo, activated charcoal is one of the most effective and cheapest odor absorbing materials. It is also used in carbon filter systems used for grow rooms.
  • Odor neutralizing agent (ONA) – This gel product is effective in getting rid of strong smells like sewage. However, it also has its own smell that may affect your plants.
  • Cannabis odor eliminator – Made of zeolite sand and chlorine. Safe for plants and humans but may affect the smell of your plants if placed closely.

Ozone generators

Price range: Around $67 (Airthereal Commercial Ozone Generator, 5000mg/h) to $279 (OdorStop OS2500UV – Ozone Generator Air Purifier Ionizer, 2500 sq/ft)


  • Effective in removing smells


  • There are associated health and environmental risks in its use
  • Can be more expensive than a carbon filter system

You may come across posts recommending ozone generators for scrubbing marijuana smells. Again, if you have one, you can probably use it in a pinch. But at its price and with the health risks associated with its use, you are much better off getting a carbon filter system.

Frequently Asked Questions

How can I get rid of the stinky marijuana smell in my grow room?

The best way to get rid of marijuana odors in your grow room is to install a carbon air filter and exhaust system. You can also use an air purifier, an ozone generator or odor neutralizing products but these won’t be as efficient as a carbon air filtration system.

What causes marijuana odors?

Marijuana is naturally smelly because its flowers are full of terpenes and terpenoids that cannabis users also enjoy.

Is marijuana odor harmful?

Marijuana odor isn’t exactly harmful to humans, but according to experts, the volatile organic compounds (VOC) like terpenes that make marijuana smelly can interact with other pollutants to make gases that are harmful to the environment.

Can I use an air purifier to reduce marijuana smell?

An air purifier, especially those with carbon filters, can be used to reduce marijuana smells in a grow room. However, they are not the most economical option nor are they the most efficient in scrubbing marijuana odors.

How often should I replace carbon filter for cannabis odors?

Carbon filters typically last for more than a year, provided that you got the right size for your setup. However, you can replace them anytime the smells get more noticeable.


When growing marijuana indoors, you won’t find a better odor-removing alternative to a carbon filter exhaust system. It is the most efficient option which makes it worth its price, it isn’t even that expensive. The next best alternative would be activated charcoal and similar odor scrubbing products since they are cheap and easily available. Air purifiers, ozone generators are not really a viable option since they are just as expensive as carbon filter systems but not as efficient in getting rid of marijuana odors.

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