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#5 Airflow for your Grow Tent – Intake, Circulation and Exhausting

October 25, 2018 4 Comments

#5 Airflow for your Grow Tent – Intake, Circulation and Exhausting

Before you grow it is important to understand the importance of Airflow for your Tent. This will help you decide what equipment you need. 

GrOh Canada’s Recommendation

When growing indoors you will need at least an inline exhaust fan and a clip on fan to refresh and circulate the air inside your grow tent. Depending on your tent size you may also need an intake fan to ensure that you are bringing in as much air as what you are exhausting – in smaller tents leaving the opening the tents side vents open will be bring enough air.

Reasons for Refreshing & circulating the air

  1. Temperature and humidity control –Circulating fresh and clean air throughout your grow room will help manage temperature and humidity levels. This is very important in reducing the risk of mold and mildew growth. 
  1. Stunted Growth– Carbon dioxide buildup in your tent can result in clogged leaf pores, which will affect the efficiency with which CO2 is absorbed and oxygen is given off. Impairing this process will result in stunted growth.
  1. Strengthen branches- A nice breeze across your canopy will help strengthen branches and stems to hold up heavy buds.

Tips for optimizing airflow

  1. Exhaust hot, stale air from from the top of the tent – Because hot air rises, the most effective way to exhaust air from your tent is to setup your exhaust system as high as possible in your grow tent. You will notice that the air vents are near the top of the tent for this very reason.
  2. Intake fresh, cool air from the bottom of the tent – You want to bring fresh, cool air into your tent at the lowest possible point of the tent.  This will support air circulation as the cool air heats up it will rise and help push the hot air towards the exhaust system.
  3. Circulate the air inside the tent with a clip on fan –Having afan inside the tent that gently circulates the air will help move air from between/under the leaves and prevent pockets of disease-friendly environments. It will also help strengthen your plants branches and stems.  
  4. Pump CO2 into your tent for extraordinary growth -Carbon dioxide is so vital to photosynthesis that enriching the natural supply can promote extraordinary plant growth.

 It is important that the warm, humid air from inside your tent be exhausted directly outside, or into a room with a window that can be opened. This way you can ensure that you are not circulating stale air back into your tent.This is critical in the summertime when there is already high humidity inside your home – if you cannot exhaust the air outside then you should not grow indoors because you will be at risk of getting mold in the room which can be very expensive to repair

4 Responses


October 13, 2020



October 13, 2020


GrOh Canada
GrOh Canada

December 29, 2018

Thanks for the question. Getting your environment right is one of the hardest parts of growing…especially during the winter. You can run your inline fan as much as needed to help control the heat, however with LED lights the heat in your tent should be fairly low so you shouldn’t need the fan on all the time. There are a few things that you can do to increase humidity

1) Open the zipper at the top of the tent door only, without using the fan

2) Use the different settings of the fan using the variable speed controller

3) Increase the amount of water inside the tent e.g. add some quarter inch rocks at the bottom of you plastic saucer, underneath the fabric pots. Add water to the stones until the water is just below your fabric pot. It will also help to put water in any other plastic, metal, glass containers with no lids to increase humidity.

4) If that doesn’t work get a small humidifier (around $40) that you can set to come on if the humidity drops below 50%.

Martin Jules Lavoie
Martin Jules Lavoie

December 18, 2018

Quick question, do i have to run my exaust fan all the time, my humidity at 30% when running 30 m on and 30 off!
My question his is it ok to run 30 min on and 1 hour off?

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