The USGS defines transpiration as “the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves”.
Odor control begins with a well sealed grow space, which means every unneeded whole has to plugged. Those opening will let odors escape, will let light in and maybe even pests.
This air exchange will also help control the humidity that will be made by those plants. The plants have pores called “stomata” and sweat during a process called “transpiration”.
When we decide to move our cannabis gardens indoors, ventilation and odor control should becomes very important parts of that plan. In part one of this series I mentioned that when I build a cabinet I use the “Grow Cabinet Triangle” to make sure most of the big questions that come up are covered. I’ve tried to put this basic information into bite size pieces that can be easily understood but that have to be considered before we put together a micro-grow or grow cabinet. In this second part I’m going to go over the other two points of that triangle which are ventilation and odor control. Some of you may think these are one in the same, but I like to split them up because I feel they’re equally important.
- Growers Note: If the cabinet size is too small for an off the shelf filter I’ll have to build one.
Knowing this, I have to make sure that that moisture is removed from the grow space because it could attract fungus or pests. Too much humidity will also slow down transpiration because it’s easier for evaporation to happen in drier, less moist air. I also have to remember that transpiration is part of photosynthesis, so it will also slow down and cause all other plant processes to slow down as well. I need to have a plan to remove the excess humidity, I say excess because a certain level of humidity is needed for different stages of growth. I like to have upto 60%-70% humidity for plants in vegetative growth and 40%-50% humidity for flowering but no lower than 20%. This is why I make sure that the thermometer that I put in the grow will give me both temperature and humidity. High humidity will also shorten the life of your carbon filter.
This type of system simply replaces the intake holes with an intake fan. This other fan is going to go over the intake hole (lower hole) and help pull in air so the exhaust fan isn’t doing all the work. With an active system the intake hole can be the same size as the exhaust hole and will be covered with a mesh or screen to keep things from being sucked in. The thing I am going to have to pay attention to is fan speed. I want the intake to move more air than the exhaust because I need to give the fresh air time to circulate around the cabinet before it’s pulled out. I’m going to make this happen be either getting two different size fans or by putting a speed control on one of the fans.
A female cannabis plants in vegetative growth will begin to smell and that smell will only get stronger as they mature. When we’re growing indoors controlling those smells is an important part of our grow space and should be taken seriously. A well planned odor control system will keep the peace in your house between you and your family or housemates because not everyone enjoys the smell of cannabis. We also have to remember that when those odors escape they become a security risk because that could alert criminals, nosy neighbors or the law to what we’re doing. It doesn’t matter if you’re in legal or prohibition land, it’s never a good time when uninvited people show up at your grow space. A carbon filter is the best answer that I’ve found by far for this problem and I have total faith that it will scrub the air clean before it leaves the space, putting my mind at ease. Another added benefit is that it’s going to remove any dust or airborn mold spores that might be floating around in the air. Carbon filters and fans come in different sizes for almost all size of grow cabinet or closets. If the space only has sprout, seedlings or clones I’m not going to worry too much about the smell, plants in these stages typically won’t give off much of an odor. But remember that if the clones were cut off of a flowering plant, they will smell.
With this type of system I’m going to use one fan to create a vacuum that’s going to pull the air in, through and out the cabinet. This fan is going to be placed over or in front of the upper hole so that it’s blowing/pulling air out. Since there is no air intake fan, I have to make sure that the intake hole (holes that let fresh air to be pulled in) are big enough so that the fresh air has time to circulate around the cabinet before being pulled out. I also don’t want to overwork the fan by making it blow out air that can’t be replace. I like to make the intake holes twice as big as the exhaust fan hole. That’s either going to be one big hole or several smaller holes that add up to the size that’s needed. All those holes should be covered with a mesh or screen to keep pests and particles from coming in.
by Alex Robles When we decide to move our cannabis gardens indoors, ventilation and odor control should becomes very important parts of that plan. In part one of this series I mentioned that when I build a cabinet I use the “Grow Cabinet Triangle” to make sure most of the big questions that come up…
Greenhouse growers should make sure they have multiple vents that can be opened and closed as required. Most basic, plastic-covered greenhouses have ventilation flaps that can be easily opened and closed manually. Worst case, you can open up the doors a little or remove a window pane or three from glass greenhouses.
Micro-growers cultivating a handful of plants or less in a cabinet or wardrobe can keep ventilation very simple. In fact, it can cost you nothing. If your micro-grow is in a spare room, you can open a window a couple of times per day to let some fresh air in. For those using LED, CFL, or lower power HID 250W lighting systems, excess heat is not an issue.
However, some promising odour-eliminating devices that can dispense neutralising agents round the clock are on the market. That being said, they are currently unproven technologies. There is also plenty of snake oil out there, so do some research and be shrewd.
The tried and trusted trio when it comes to eliminating cannabis odours are hands down the intake fan, outtake fan, and carbon filter combination. If you are already investing in fans and ducting, it makes sense. For the grower that wants to be certain that odour is under control, this system is the best.
Most home growers grow weed in grow tents. Modern grow tents are designed to house your ventilation system. All you need to do is put together the right kit. Ideally, you should be considering ventilation as part of your initial grow plan. The lights you choose and the size of your grow space will dictate the type of ventilation system you must utilise.
Air should be exchanged every 1-2 minutes in order to maintain optimal temperatures and humidity. The aim is create negative pressure or suction. So you want to see the walls of the grow tent sucking inward when your ventilation system is up and running.
The four pieces you can’t do without are an intake fan, exhaust fan, ducting, and duct tape. If you want to mount your extractor fan inside the roof of the tent suspended from the poles, use chains or cable ties to secure it in position close to the ventilation hole. That will be in the top corner of the tent, or actually in the roof depending on the model.
Your intake fan needs to be positioned near or at ground level to connect to the hole in the bottom corner of the grow tent. Keep that ducting straight and use duct tape to secure in place. Again, the external ducting must connect to a source of fresh air, ideally a vent or window. Later, we explain how to do this discreetly.
Outside ducting will need to connect to a vent or window to exhaust hot air from the grow tent. Inside the grow tent, it is also important to maintain good airflow. Clip-on fans or an oscillating fan is all you need to create a light artificial breeze. Take care they are not too powerful or positioned too close to plants or they could suffer “wind burn”.
Ventilation is a critical factor of indoor cannabis cultivation, and in the greenhouse. Find out how to ventilate your grow-op and avoid trouble later.