When to turn on the exhaust fan

Is it time to turn on the exhaust fan? I have a 600 watt Apollo exhaust fan that draws 440 CFM in a 2’ x 4’ x 6’ 7" tent. I have just transplanted for the first time from solo cups to 1 gal soft pots. The humidity has been under 50% while the plants were in the solo cups. I did not think the humidity was high enough with the seedlings in the solo cups to need the fan. Plants have been in the 1 gal soft pots for an hour and humidity is still 47%.

Got any pics? I think temps will drive when you need to turn on the fan. Temps shouldn’t get much more over 85 degrees (they can survive higher temps but there may be other issues that come of it). If your plants are established, they will take 50% humidity just fine.

Are they seedlings or clones? Clones need a lot of humidity as where seedlings do not. My intake and exhaust fans run 24/7 to maintain airflow and to filter out the air in the tent.

These are seedings. I transplanted today for the first time as they leaves reached the sides of the solo cups.
I thought I might want to start using the fan because there will be more water and that should increase the humidity. I do not have an intake fan, although I do have a couple of fans inside to move air around.

The temperature runs just a bit higher than the rest of the house, which is no more than 65* (I can’t tolerate a too warm house). It has gotten up to 70* in the tent. Will humidity will increase since I am using more water for the 1 gal smart pots? Eventually, these will be in 7.5 gal soft pots, which will of course require much more water.

Yes, I see humidity increase in my tent now that I am in larger pots.

Temp, food, media and light ALL have to be within the range acceptable to the plant.
Some strains are more cold “comfortable” than others.

As to the exhaust fan, my light and exhaust are both on auto-timers and set to start at the same time. At night, the exhaust runs 20 mins longer than the light.


So it is not necessary to run the fan 24 hours a day? I could put in an additonal timer for the exhaust fan and I suppose the small fans used to move air and slightly move the leaves.


main function of exhaust fan is to take out excess heat. usually when the lights are on.