air pressure question?

My question is is it better to have a positive air pressure or a negative air pressure in your grow space? Also how much air flow is good, like the whole space being refreshed once a min good?

Here's a calculator for estimating air flow and exchanges.

http://botanical.com/hydro/air/calculating_fan_requirements.html

The negative versus positive is fairly pointless as your exhaust fan moves a certain amount of air. If it moves more than your intake fan can supply the sides of grow tents "cave in" as the air is exhausted. If your intake is larger the sides will billow. It makes sense to have them equal or the exhaust fan just slightly larger to make up for changes in room pressures as doors and windows are opened. Judging how effective your system is by declaring how far the sides of the tent cave and declaring that good is misguided.

You want to create a negative pressure. Try to calculate your intake to exhaust where it is close to a 1:4 ratio.

Я не совсем согласна с автором.

Olyapatta said:

Я не совсем согласна с автором.

Click to expand...

.............what he said !

you want a negative pressure. if smell is an issue and you dont have a 100% sealed room, then the smell will leak out with positive pressure.

1 exchange per min. is good but if heat is an issue then 3-5 times per min. may be needed.

Thanks guys, its not a tent its a closet and smell is going to be an issue with more plants. So the neg press would prob be better so more air would pass threw the filter.

Negative pressure contains smell (in comb. with a filter).
Positive pressure dissuades flying pests.
Most folks are more concerned about the smell. cn