Do i need to have a fan exhuast air from 2x4 grow tent?

I have a 2x4x5 tent. My set up is pretty good I think, I’m just curious if there is anything I’m missing. I’m gonna attach a few pictures, this will show you what equipment I’m running, vents I have open on tent. After you see pictures, here are my questions. White fans are on max, but they produce very little air movement, the black fan is set to its lowest setting as it pushes air pretty good. Plants move just slightly, but are moving constantly, just not too aggressively. I have a Spider Farmer 2000 LED light. 18/6 schedule.

I little background on my home and tent location. I have a manufactured home, 200 sq ft. I use one on the bedrooms for my tent, the house is pretty much always open, most all interior doors, and there are 2" gaps under doors throughout. My HVAC system runs duct work under the trailer, and has up draft vents on the floor. Windows are open during nice weather. AC kept at 79 in summer.

When I run the AC Infinity 6" fan on the lowest setting (1), my humidity controller is set for max 47.5%rh. But I can only get to about 38%rh. I live in the Phoenix valley, and the current ambient temps during AM hours are about 72 degrees (f). In the AM the canopy temps are 75-76 degrees approx. The humidifier is currently set to level 1, but even when I set the humidifier to max, the RH only gets to 46%. As the temps raise throughout the day, the humidifier doesn’t have to work as hard due to the increase in temps. I guess my question is, do I need to run my AC infinity fan constantly? I liked the idea of it expelling the hot air at the top of the tent. Anyway, anything you could tell me would be great. I do not use a CO2 supplement, maybe I should be? One more addition, when I run my humidifier on max, its only 1 gallon, so I have to fill like 2-3 times a day, and that gets old. Is 38% rh good enough for flower, or should I really be shooting for just under 50%? Sorry so long, just hard to explain in two sentences


Thanks in advance.



You don’t have to have an exhaust fan, but it helps a lot. You do have to have good airflow.

Your temps are fine.


CO2 isn’t going to help with the light you have. You need to be pushing 1,000 PPFD and higher if the plant is to use the extra CO2.

I really appreciate the feedback. I set the humidifier to #2 setting of 3. The AC fan is on setting 1 constant. It’s holding at 41.5rh, and temp at 76f. As the day gets warmer, the temp and humidity will rise to the max 47.5rh and 80-81 degrees. Are those still safe numbers? If you wouldn’t mind, can you tell me danger zones for heat and humidity? There have been times when the text was at 85-87 degrees, but that was in the warmer months. Is that still safe? Thanks again.

Low to mid-80’s is fine for temp. I’d say that the ideal temps for cannabis is in the high 60s to high 80s for temp.

I’d want to keep humidity higher than 30 and lower than 50 for flowering. You can go higher in veg. High humidity in flowering risks mold/mildew problems. I wouldn’t go higher than 75% RH for any stage of growth.

Perfect, that is where I kind of am at. I have two tents, one currently has a white widow in veg, so i set RH to 60%. That is a small 27" x 27".

Anyway thanks again.

Here is a VPD chart that will help show you the optimal temp/RH values for the differnt stages of growth.

1 Like

Thank you, much appreciated.

1 Like