Growing your own cannabis indoors in small numbers (a few plants) is not much of a hassle, but scaling up indoor cultivation, even with the use of a grow tent, can produce plant odors that overwhelm and make living in the same building as your crop extremely annoying. There are, however, several means you can employ to mitigate smells from your grow room.
Here we provide you with our recommendations for odor-free (or at least, low odor) growing that will make living under the same roof with your crop tolerable.
Use a Grow Tent
Using a grow tent is a one-item solution that typically eliminates about 70-75% of cannabis odors. Many grow tents are commercially available in a wide range of sizes and can be placed within an indoor room.
Cultivating your plants in a grow tent will take care of many odor issues and is a relatively simple solution. The enclosed space also makes it much easier to control temperature and humidity in the grow space.
Most grow tents are pre-built with electrical and ducting ports so that you can mount grow lights inside and connect hoses to exchange air for humidity and temperature control.
Control Temperature and Humidity
One of the first things you should try when approaching the odor problem is to control growth conditions. By simply altering the temperature and humidity of your grow room, you can affect the amount of volatile organics your cannabis crop shares with you.
Under most growing conditions, cannabis produces little odor. However, approaching and during the flowering phase, cannabis plants begin to produce higher levels of terpenes, which are the main volatile organic compounds in the plant’s odor.
High humidity and temperature foster odor production in any plant. Keeping your temperature levels below 27°C (but no lower than 21°C) and grow room humidity below 30% will help reduce plant odors.
This can be accomplished with a standard room dehumidifier to control humidity and a standard room air conditioner (which will control temperature and, to a lesser extent in the temperature ranges for optimal growth, humidity).
These changes do help control plant odor quite a bit, but will not do the job on their own. You will need to apply additional measures to keep the environment relatively odor-free.
Improve Air Circulation
Proper air circulation can be facilitated by use of exchange fans, either an intake fan or an exhaust fan will do. Make sure to have an exhaust vent (for intake fans) or an intake vent (for exhaust fans) to assist in providing good air exchanges.
Use of fans for good circulation will greatly assist in (1) air cooling, (2) removal of volatile plant organics, and (3) maintaining good levels of CO2 in the grow space.
Proper lighting for good plant growth is necessary for cannabis cultivation, however many types of grow lamps produce modest amounts of heat. This will make controlling the grow room temperature challenging, since the air near the lamps will always be quite a bit warmer than the intended room setpoint.
Using full spectrum LED lamps intended for plants will provide all the light you need without all the excess heat. Typical LED lamps run a bit cooler since they do not produce much infrared radiation.
As an added bonus, LEDs use about 50% of the electricity of fluorescent counterparts and are attuned to produce light at wavelengths optimal for plant growth (not necessarily optimal for reading a book).
Lower temperature lights reduce local heat eddies in your grow room. Cooler grow lights combined with improved air circulation collectively assist in maintaining proper air temperatures and air circulation.
Use Carbon Filter Air Cartridges
Another effective method of control plant odor if you are growing a lot of plants indoors, and one that at that level of cultivation is an absolute must, is the use of carbon scrubbers. Carbon scrubbers are activated carbon cartridges that chemically absorb volatile organics in air passed through them.
Use of carbon scrubbers requires a ducted fan (preferably an exhaust fan) and ductwork to attach to the scrubber cannister. The easiest means of using a scrubber is to make it a component of your grow tent/grow room exhaust system.
Scrubbers come in all shapes and sizes, so which one should you use? When selecting a carbon scrubber, make sure that the flow rate matches your exhaust fan.
For example, if you buy a 400 CFM (cubic feet per minute) filter and hook it up to your 600 CFM fan, there will be problems. The fan will pull air through the filter faster than the activated charcoal can bind the volatile organics, so you will not have efficient odor control.
We recommend using a 6-inch scrubber and ductwork with 6-inch exhaust fans since there very practical reasons for using this size. Smaller fans (like 4-inch fans) cannot produce the flow rates necessary for good air circulation and cooling, whereas larger fans (like 8-inch fans and greater) are really, really expensive.
Also, any air-cooled grow lights also have a 6-inch port, the most common size. Combining your 6-inch intake duct (preferably with a hood) with a ducted grow light, a 6-inch scrubber, and a 6-inch exhaust fan produces a two-birds-with-one-stone system to draw in cool air, cool your lamps, filter, and exhaust your grow room air all in one package.
Use Odor-Absorbent Gels
There are many odor-absorbing gel products out on the market from which you can choose. They work in a similar manner to activated carbon, but have a much shorter lifespan than a carbon scrubber.
Bear in mind, however, that gels are not, repeat not, greenhouse products. Think of them as fancy-schmancy air fresheners.
Anti-odor gels are for use in your living or office space as an assist to reducing grow room odors (place them near your grow room exhaust port). Do not use them in your grow room (despite what you may read on other sites) since they can alter the chemical constituents in your plants.
Ozone Generators (do not do this)
Without a doubt, ozone generators will completely crush any smells coming out of your grow space. They will also harm your plants, although many sites advocate using them.
We all like ozone, it’s our friend, high up in the sky keeping us from getting completely crisped up like breakfast bacon. However, many chemicals in our world are excellent in one place and very, very bad in another.
One of those chemicals is ozone. In the upper atmosphere, golden, down here on mother Earth, a pollutant (that’s why it is banned in California).
As ozone is wrecking volatile organics to remove the smell, it also will be working over your plants. Ozone works by oxidizing (chemically altering) target chemicals, which includes those in your crop.
Just stick with our recommendations above and leave out this last, nuclear option. Happy growing!