Positive pressure issue

I have a legal medical grow with a 8x4x7 flower room and im having issues with positive pressure. I have a 10in inline fan attached to a carbon filter matching the CFM of the inline. For my intake i have 300 CFM unit. I have tried everything and can't figure out the problem. Ive been reading on this forum a lot but never made an account, this seemed like the best place to get a good answer! Hope some one can help!

Can you turn the level down on your intake?

ya, I've turned it down to the lowest level and theres still air coming out when the door is open. I haven't had time to check how the temps get when its down though. At this point its worth risking the temps for couple of days to see!

yeah I see what you're saying. Do you have a fan controller on the fan for the carbon filter outtake?

Is it really that much of a problem? This is probably normal because of turbulence in a small area, but I think I know what you mean.

When the door is closed is there any air coming out the other passive intakes? There shouldn't be.

Just turn the intake fan off when you open the door.

- Jiji

It wouldn't be a problem at all if there wasn't a problem with smell, with a couple ladies in there that are deep into flower the smell is pretty noticeable. What do you mean turbulence? and yes there is air blowing out of the passive intake. Im stumped, I've tried everything. Even using duct tape to seal one of my hoods thats isn't being used in there right now didn't work!

Do you have your fan on backwards, blowing air into the area? LOL, but I don't see how a 10" fan sucking through a carbon filter in a 4x8 space wont' create negative pressure. I have a 4x8x7 grow tent and a 6" 440cfm fan attached to a carbon filter sucking air in the tent and then using that to exhaust through the lights out the basement window. I only use the passive air intake flaps on the bottom for intake. I would try to use passive intake only. On my tent, if all the intakes are closed, it will suck in the walls really hard, as I open the flaps on the bottom, it eases tension until there is not much tension on the walls, but it's still plenty of negative pressure. At first i had a small fan blowing air into the tent while sucking out and realized it just needs passive intake. A fan that size should suck in plenty of air.

This is an old image how i first set it up and you can see that tube in the background was a fresh air intake hooked up to a fan. I took that out and only use the flaps on the bottom.

Yeah, for my tent, which is a 78x78x78, I have a 6 in inline duct fan for my intake running 24/7(I do run a timer on it in the colder times of the year so I don't have cold air blowing in while my light is off.) My carbon filter has a 440 ccm 6 in blower hooked up to a fan controller running at about 3/4 speed and I always have negative pressure. (walls of tent suck in). Never had an issue with positive and negative issues, at least the plants don't seem to mind it.

Tyler S said:

ya, I've turned it down to the lowest level and theres still air coming out when the door is open.

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door is open = no negative pressure potential.

Lol I laughed pretty hard at the fan on backwards idea.

Seriously though, without that intake fan on and the door shut, Unless you have a ton of passive intake area, and even then, the walls of your tent should be majorly sucked in.

What brand and model is the 10 inch fan? I'm guessing its not centrifugal. And your pulling through two hoods?

- Jiji

Tyler S said:

I have a legal medical grow with a 8x4x7 flower room and im having issues with positive pressure. I have a 10in inline fan attached to a carbon filter matching the CFM of the inline. For my intake i have 300 CFM unit. I have tried everything and can't figure out the problem. Ive been reading on this forum a lot but never made an account, this seemed like the best place to get a good answer! Hope some one can help!

Click to expand...

Is the 10" inline an exhaust? Edit: Just saw your pic. I see no exhaust at all.

jijiandfarmgang said:

Lol I laughed pretty hard at the fan on backwards idea.

Seriously though, without that intake fan on and the door shut, Unless you have a ton of passive intake area, and even then, the walls of your tent should be majorly sucked in.

What brand and model is the 10 inch fan? I'm guessing its not centrifugal. And your pulling through two hoods?

- Jiji

Click to expand...

Yes im pushing through 2 hoods and i have a another 6 inch outside pulling.Its a 10inch hydrofarm inline. I've been trying a a few things. I think one of my issues was to much air being pushed in and i had a hood that the glass wasn't sealed very well on. It did get better, just watching to make sure temps don't go up. The plants aren't effected at all, they are better then usual! I'm just concerned about the odor. Thanks for the help everyone!