30% humidity jump from nowhere question.

[CF89]

4x4 tent.
480w kingbrite light
6 plants
5 gallon fabric pots
1:3 promix and perlite
General hydroponics nutes
5 weeks into flower


Ok lately I’ve got pretty much a sealed tent. Not much of an intake air but I do got a weak 6” exhaust fan with a carbon filter. Usually the tent is imploded inwards and has a negative pressure. Perfect. Usually the tent is 35-40% RH at the most.


My basement is also around 35%. I have like 5 humidity meters.

Here’s where it gets weird. I decided to open a vent flap up a little on the bottom of the tent for more intake air. Just to see... and an hour or so later the basement stunk like weed and the tent humidity was 60%. How?

Did opening the flap totally render my little struggling exhaust fan useless and the humidity raised from the plants?

They were watered 4 days ago and are due for water in 2-3 days

Pic: right gauge is the tents numbers. The left is my basement

 

[CF89]

The exhaust air seems to be quite humid compared to the tent (which has dropped 10 degrees in 10 minutes)

I wonder if my charcoal filter has moisture in it?

 

[Aqua Man]

Because plants transpire. This will only become more pronounced as they get bigger.

 

[MIMedGrower]

The plants give off the moisture. Every drop poured in is eventually transpired back into the air. And yes when you open the tent you stop the negative pressure and so some humidity escapes into the room. And relative humidity changes very quickly. Especially when introducing vapor to a dry room.

 

[MIMedGrower]

Because plants transpire. This will only become more pronounced as they get bigger.

Lol. I know i started posting before you but you stated it very simply and i am still babbling. Lol

 

[Aqua Man]

Lol. I know i started posting before you but you stated it very simply and i am still babbling. Lol

Happens to me all the time lol

 

[CF89]

So where did the humidity come from?

all I did was open a vent flap on my tent and exposed it to intake air from another 30% room

 

[MIMedGrower]

So where did the humidity come from?

all I did was open a vent flap on my tent and exposed it to intake air from another 30% room

You stopped exhausting it and the vapor immedietely fills the space.

 

[FFM]

Here’s where it gets weird. I decided to open a vent flap up a little on the bottom of the tent for more intake air. Just to see... and an hour or so later the basement stunk like weed and the tent humidity was 60%. How?


I just can imagine the pressure is too weak, if you`re open up a vent flap.

If you have not enough air change/pressure in your tent,
humidity will climb up. ( temperature too)
The air is not being renewed fast enough, air begins to accumulate.

The carbon filter needs a minimum pressure to work well.
If less under minimum, it starts smelling...
58 % RH is not a problem for a good carbon filter

If I play with my exhaust fan and my carbon filter...

First pic: Everything ok for me in Flower.

...after 12 minutes, only changing exhaust air / pressure ( to under minimum ) and open a vent flap.
Second Pic: its all climbing up

and the RH from the surroundings is lower than tent RH

Maybe something like this.
Good luck.