Grow tent ventilator: How strong should it be?

Are you choosing air conditioning equipment for your grow tent or room and wondering which ventilator is the right one? We will help you find the appropriate ventilator capacity in this article.

As you surely know by now, fresh air plays a vital role in indoor growing. Plants need the appropriate amount of oxygen and carbon dioxide to develop healthily. Badly ventilated grow tents are also prime breeding grounds for moulds and diseases.

Picking a ventilator with the right capacity is key. There is a plethora of different ventilators with different outputs available and figuring which one is perfect for a grow tent can get overwhelming for beginners. You don’t want to buy a weak ventilator which won’t last or a too strong one and waste money.

We express the capacity of ventilators in m3/h (cubic meters per hour), which describes the amount of air (m3) the ventilator moves in an hour. Capacity is marked on a curve, and the point at which the ventilator works best is sometimes described as the optimal capacity. Maximum capacity is the highest amount of air the ventilator can move in an hour.

The easiest way to go about picking the right ventilator is by looking at the lighting setup.

Growers who use HID lamps have it easier in this case. HID lamps produce a lot of heat, which has to be removed somehow. The basic formula also counts in a carbon filter and at least 5 m of air ducting. 

  • For HID lamps, 1W of the light’s power = 1m3/h of the ventilator’s capacity.

For example, if you’re growing under a 400W HID lamp, you should use an outtake ventilator with a capacity of at least 400m3/h.

TIP: We recommend using two ventilators, one for the outtake and one for the intake, to prevent negative pressure in the tent. VKO ventilators are very good for smaller spaces, and TT ventilators are better for larger areas. 

20037-5Using LED lights for indoor growing isn’t just a fad. They provide better results and pay off in the long run because the lights are more effective, need less electricity and produce less unnecessary heat. You won’t also need such a strong ventilator as for grow tents with HID light.

If you’re lighting your plants with an LED or CFL light or an HID lamp with a cool tube, you should determine the capacity of the ventilator like this:

  • Calculate the total air volume in the grow tent or room and multiply it by 40. The resulting number is the capacity your ventilator should have.

For example, if you’re using the Mammoth PRO+ 120, the calculation is: 2,88 m3 x 40 = 115,2. You should pick a ventilator with the capacity of at least 116m3/h or stronger like this one capable of creating airflow of 150m3/h.

If you don’t know the air volume of the grow room or tent, you can calculate it like this: 

  • Height (m) x length (m) x width (m) = air volume (m3)

As you can see, the basic formulas are pretty simple. However, it can get tricky if you’re equipping a large tent or an unusually shaped room or want multiple fans for ideal air circulation. Any complications, like increased heat in the grow tent, turns and reductions in the ducting, filters or silencers need to be accounted for as well. 

If you’d like to consult an expert before spending any money, contact us at

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