In an indoor culture we always try to reproduce what happens in an outdoor culture, so the lighting for the sun, the fan for the wind.
The interest of the wind is that it will improve your plant at the level of the trunk, which will allow it to be much more solid and suddenly lift a lot more fruits and flowers without it breaking afterwards. It's like a person who trains, she will carry more and more heavy loads over time so here your plant will raise more and more flowers afterwards and suddenly have a better harvest.
The advantage of having a fan is that it will stir the air in your grow room, thus avoiding mold and disease.
The advantage of LEDs:
LED lighting is reputed not to heat up or much less than HPS, because HPS lighting gives off radiant heat so you will find a significant temperature rise in your plants, while on LED lighting you will find a rising heat so a large part of the heat released by your lighting will be found above.
It is for this reason that in a culture under HPS you will find more fans to stir the air and move the hot air upwards.
With LED lighting you don't have this problem so the fan will really serve to solidify your plant.
Choose your Fan:
To choose the right fan, we first need our cultivation area.
For a culture of 60 cm by 60 cm I advise you to choose a small fan.
Here are different fans that may be suitable for 60 cm by 60 cm:
If you have a larger grow box (like an 80cm x 80cm room), I recommend getting medium-sized fans.
Here are different fans that may be suitable for 80 cm by 80 cm:
For large culture rooms (greater than 100 cm by 100 cm), I advise you to take a pedestal fan.
Here are different fans that may be suitable for 100 cm by 100 cm or more:
You can also combine several fans as quoted when your growing space allows you. For example, put several clamp fans high up and put several foot fans on the ground.
It all depends on your setup and preferences.
Timing of a fan:
The timing is a question that you ask us a lot for ventilation so we will answer it! Your fan can run 24/7, there is no problem, however if you have to choose between noise and ventilation, I advise you to run the ventilation during the day and during the night to stop your fan.
Important point: only run your fan during the growing medium to flowering phases, especially during flowering to avoid mold.
Avoid turning on your fan for small cuttings, small plants, young shoots, as this will dry out the soil and therefore your plant will not be able to feed properly.