How To Set Up Ventilation In A Grow Tent

Proper ventilation ensures that fresh air is circulated throughout the grow space, providing plants with a continuous supply of carbon dioxide and preventing the buildup of excess heat and humidity. Carbon filtration, on the other hand, helps to remove unwanted odours and purifies air as it leaves the grow tent. 
Ventilation and carbon filtration create an ideal environment for indoor horticulture, supporting healthy plant growth and maximising yields.

Many indoor growers choose to operate their ventilation to keep a negative pressure inside the grow space, this means that the air pressure inside the tent is lower than the air pressure outside the tent. This is typically accomplished by using an exhaust fan to pull air out of the tent. The benefits of operating under negative pressure include improved air circulation, and better temperature/ humidity control, reducing risk of pests and mould. By pulling air out of the tent, growers can ensure that fresh air is constantly being pulled in, which helps to prevent stale, humid air from building up.
Operating negative pressure is ideal for effective simple carbon filtration setups.

Gardeners who choose to use positive pressure ventilation are less common, it is best used where carbon filtration is not required, and an intake filter can be used instead to remove spores, pests and contaminants before they enter the grow space. 
The benefits of a positive pressure approach are improved air circulation- which helps to distribute CO2, and exclusion of pests and pathogens when an appropriate intake filter is used. 
Positive pressure growing is not ideal for carbon filtration and may require more energy to maintain.

Ultimately, the choice between negative pressure and positive pressure indoor gardening will depend on the specific needs and goals of the gardener.

For a gardener using a single fan as an exhaust, there are a few configurations to locate the fan and the filter as pictured below. 
It is vital that the fan draws air from the top of the tent because hot air rises, and it is a good idea to have the fan suck air from the filter rather than blow through (see preferred method).

Discerning growers may choose to use an intake and exhaust system for ventilation. The intake is responsible for bringing fresh air into the tent, while the exhaust removes stale air and heat. Typically, an intake fan is positioned near the bottom of the tent to draw in fresh air and circulate it around the plants. The exhaust fan, on the other hand, is positioned near the top of the tent to remove hot, humid air. It is important to ensure that the intake and exhaust systems are properly sized and balanced to maintain optimal temperature and humidity levels within the grow tent.

To correctly size an intake fan for a negative pressure grow room simply select the next size down from your exhaust fan, i.e for a 200mm exhaust fan choose a 150mm intake fan. Some fan controller options allow for a variable differential between intake and exhaust fan settings. 

There are many options for configuring ventilation, it's a good idea to consider your options and maintain ventilation as a priority when setting up your indoor garden.
Proper ventilation is crucial for successful indoor gardening, without adequate air circulation, plants can suffer from a lack of oxygen, increased humidity, and the buildup of harmful pollutants. With the right ventilation strategies in place, you can enjoy a thriving indoor garden all year round.