This high-velocity ground fan by Brons with 40 watt power can be set in three stages up to a rotation per minute of 1280.
The solid metal construction is chromed and classically designed. The rotor-blades are of metal as well.

ø 32 cm
40 Watt
220-230 Volt
1280 RPM
3 kg
 

Noise (own measurement):

Level 1 - 70 dB

Level 2 - 77 dB

Level 3 - 84 dB

A ground fan in use should always aim upright to the ceiling, to provide the rotation of the air. This is important for the CO₂ regulation, because if the air rotation didn't take place, the air, that's surrounding the plant would be exhausted too fast.
Another reason for the need of ventilation is the growth of the plants. We simulate wind the way it would occur in the nature what makes the stalk stronger - the same way as sports would strengthen a person -. You're plant will need a stron stalk to be able to carry all the crop that we're looking forward to.

You should also make sure, that your fan is not blowing directly towards your plants, because this would cause problems, too. Blowing directly on the plants results in blowing tiny little drops of water off the leaves. The leaf becomes dry. At the end, your plant  would simply dry up, although the humidity in the room is fine. That's why you adjsut the ground fan upright towards the ceiling.

To find out, whether your fan is positioned right, watch your plants, if every leaf - even in the backmost corner gets moved by the fan, than it's okay. If not, you shoul find a new position for the fan or replace it with a stronger one.