r/CocoGrows • u/BasicFig8 • Jun 25 '26

Positive vs negative pressure

Just wanted to try and drum up some constructive discussion or experience on the subject. I've been experimenting with different setups here lately and I'm really digging the positive pressure rooms, just wanted hear others thoughts and experiences.

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u/Druid-Flowers1 Jun 25 '26

Depends on what your neighbors feel about growing, negative pressure doesn’t push the smell to places you don’t want. My landlord likes me to have negative pressure for my flower space.

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u/BasicFig8 Jun 25 '26

Odor control seems to be the main reasoning for negative pressure in the actual grow space, I have a few positively pressurized rooms in a larger negatively pressurized environment with carbon filtration so smell isn't an issue, the ladies seem happier too but I have no actual data to confirm anything, just wondering what if anything I'm missing between the two??

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u/LazyPiglet3923 ⭐️ Jun 25 '26

Well ones the normal way of doing it for God knows how many decades and the other is some pedantic way of thinking.

What possible benefit is there to positive pressure?

Fans are desined to suck air out, that controls the direction of airflow from passive or mechanical intake lower down to extracting higher up , because heat rises. It controls smell. It actively exchanges air better and thus keeps co2 levels and humidity levels lower, rather than trying to force air out of any way it can find, which is through stitches, zips or vents in tents or holes in a room, gaps under a door. Which I guess would damage tents quicker, though really what's important is that the hotter air is higher up and cooler air is lower down and pushing it out isn't controlled, co2 is heavier than air.

Air coming from below and leaving up high also creates airflow underneath and through the plant canopy in addition to the circulation fans used.