Too Much Negative Pressure in Grow Tent – A Complete Guide For Beginner

(Last Updated On: August 17, 2021)

Too Much Negative Pressure in Grow Tent? Here is a Complete Guide For Beginner.

A grow tent is an easily movable, growing room for hobby growers who have limited space in their homes and are available in a variety of shapes and sizes. 

It can easily be reused and its components include a canvas that makes the exterior, an interior that is highly reflective to increase their efficiency, and consist of some ports to facilitate the integration of proper ventilation, lighting, and other necessary components.

Cannabis growers have been the biggest adopters of grow tents, using them to cultivate Cannabis crops indoors, however recently there has been a surge in uptake of grow tents by other crop producers.

Grow tents are important for taking care of wilted or unhealthy plants and can provide ideal conditions for the regeneration and recovery of the whole plant. Plants that are sensitive to specific conditions like temperature variations, humidity changes, or lighting changes can also be cultivated in a Grow tent.

What Is Negative Pressure In A Grow Tent?

Too Much Negative Pressure in Grow Tent
Too Much Negative Pressure in Grow Tent

Negative pressure in a grow tent indicates to have lower air pressure within the interior of the grow tent as compared outside. 

It occurs when the quantity of air exiting the grow tent through the exhaust fan is more than the amount of air incoming through the grow tent.

Negative pressure has some benefits especially to the plants growing inside the grow tent;  it can enable easy management and optimization of conditions like temperature, humidity, Carbon (iv) Oxide, and contaminants.

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So that too much or too little of them don’t interfere with the growth of plants,  second it protects plants in the tent from being affected by fungal diseases like mold and mildew and also helps eliminate bad smell from the tent.

Positive Pressure verse Negative Pressure Ventilation

 How To Maintain Negative Pressure In A Grow Tent

Because slight negative pressure is good for plants and enables gardeners to maximize yields it is crucial to be maintained.

To ensure that the tent has the right negative pressure, the gardener should first determine the cubic feet per minute of the grow tent ( CFM)  which is a method of determining the rate of air movement into and out of the grow tent.

To get the CFM, the gardener multiplies the width, height, and length of the grow tent and the value they get is the cubic feet. Because air is always replaced after every 3 minutes, so the cubic feet value will be divided by 3 to get get the CFM value. 

The CFM value that the gardener obtains means that he should source for inline fans for grow tent that can handle that CFM value, hence basically CFM is the quantity of air that will be exchanged every minute.

How To Reduce Too Much Negative Pressure in A Grow Tent

How To Reduce Too Much Negative Pressure in A Grow Tent

Too much negative pressure can be bad for plant growth, hence should always be kept in check. Some of how it can be reduced include; using active intake instead of passive intake.  

A fan speed controller can also fix negative pressure by controlling the air movement in the exhaust fan. A gardener can also manage negative air pressure by integrating a good number of extra ducting intake at the lower part of the tent.

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Experts do recommend adding up to 6 ducting intakes for tents measuring at least 50  square feet. To fit a ducting intake onto the lower part of the tent, you place a cardboard box with some openings on three of its sides.

This setup makes the ducting to prevent light from penetrating it and the bigger its diameter the more air it can draw to eliminate too much negative pressure.

The gardener can also design the ducting in a way that it appears ‘ S’ shape to ensure that it efficiently blocks light from going through it. Canvas layers, duct cloth, gaffers tape, and placement of the duct opening in the dark side can also make the whole tent lightproof.

Lastly, a light-proof vent flap that comes already integrated at the lower part of the tent can also help in overcoming excess negative pressure when it is opened and works with the intake fan to draw more air in.

Is it better to have a positive or negative pressure in a grow tent?

Positive pressure is created in a test environment when more air pressure is pumped into the tent than what needs to be exhaust. The pressurized air that is exiting the tent can create an efficient barrier to prevent pathogens from entering into the tent to infect plants.

However, it is hard and also expensive to produce and maintain such conditions. The conditions may also remove most of the odors within the tent.

Negative pressure which is well articulated in this article is better than positive pressure conditions because it retains most of the odor in the system, provides optimum atmospheric conditions that are a replica of the external environment and this allows crops to grow optimally. 

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Its main limitation is that it can introduce pests and disease-causing pathogens, hence infecting plants in the system.


In conclusion, grow tents have indeed revolutionized how plants are grown especially in the urban areas where land or gardens for growing crops is scarce.

They are cheaper and easier to install and their durability makes them reusable and interior conditions can be modified to create conditions of positive pressure, negative pressure, or hybrid that are ideal for specific plants.

Gardeners should consider creating slightly negative pressure in their tent as it provides nearly optimal conditions for the growth of most crop types.

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