Negative tent pressure

[DougDawson]

I guess there is a point to be made and that is how much air exchange do you need? There is only so much air exchange the plants need. I normally turn my fan up to the point where it starts sucking the walls in, if it goes in too much I fine tune it. That way I always have negative pressure but am not over working things. I do like the negative pressure kits folks are posting though. They would also come in handy for other things like clipping on a fan or tying off a plant.