Fans

How to calculate the necessary fan capacity for a room

((room volume in m³) + (30% of the room volume since the filter might reduce the performance ) ) * desired air exchange frequency.

If we assume a room size of 20m³ and we want to exchange the air 12 times per hour we get the following result:
(20 + 20/100 * 30) * 12 = 312m³
Thus, we need a fan that has at least the power to achieve the air flow of 312m³ per hour. Yet, this calculation applies only to duct hoses less than 1m long. If they are longer, you need to take the length into account also. So for let's say 3m long hoses you calculate:
( (20 + 20/100 * 30) + 3) * 12 = 348m³
You'll need a fan with a power of approx. 350m³ per hour.

Fitting Sizes of fans and filters

The connecting sizes for the parts are standardized. Depending on the fan capacity they usually range from 100mm to 315mm. If you already have a fan or filter and the other part does not fit you can get a reducer.

Intake Fans

If the grow room only requires fresh air for a higher oxygen amount, simple intake fans should suffice. Just put one into your duct hose.

Air Flow Control

For your environment control (duration of fan operation and power) you can use either simple timers or special fan controllers that can regulate the temperature or air humidity.