So what googled my question and got so many different answers I figured I’d come here and directly ask the forum that I think is the most knowledgeable.
My tent has two passive vent ports in it. There’s of course some air coming in the other holes (like for the power cords). Should I leave those ports open or closed? I’m not terribly concerned about light leaks because it’s full dark whether they’re open or not. I’d kind of like to close them because I’m not sure I can achieve negative pressure otherwise, but I want to be sure there’s enough fresh air getting in. My fan/filter is outside the tent, so air is getting pulled out.
So yea, ports open or closed? I appreciate your help
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There isn’t a definitive “correct” answer and it’s up to you. Do what is best to maintain good airflow through the tent. It’s important for temp and RH management, as well as CO2 replenishment.
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It depends on the stage and environmental factors in the lung room and grow space. If your grow space space is warmer than you like, you can open them and then adjust your exhaust to get your space where it’s needed.
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I pull in as much fresh air as I can while keeping my Temp and humidity at the level I want. So I set my heater and humidifier where i want them to be, and run my exhaust fan at a level that won’t overrun the temp and humidity levels.
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I open or close these ports depending on my lung room/tent conditions or to relieve some of the negative pressure. When I want some of the cooler lung room temps to be brought into the tent using the draw from the exhaust fan I’ll open them, when I want higher temps and RH for the seedling or veg period I’ll leave them closed 
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If my tent is all over the place I’ll open them up. I have an inline fan pulling fresh air in though so it’s not a requirement, just something I play with from time to time.
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I have a combo of auto and photos in the same area. I use 2 6 inch vent hoses to pull in air and no light. The other tents I generally have one open for air flow and remove heat from my lights.
You need to replenish co2 consumed by plants at least while lights are on. That is the purpose of the passive intake vents anyway. Nothing says you need them all 100% open to achieve this but probably at least one of them partially open or some other means of getting unrestricted flow of fresh air in. I have 6" port on bottom of my tent and I use flexible duct here in the shape of an S to prevent light from entering. I wouldn’t expect enough air to come from leaks at seams and zipper.
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Thank you all for the replies.
My “lung room” is just my shed, so it’s not insulated. I’m very much prone to the elements. I do have a radiant oil heater, a portable a/c unit, and a legit dehumidifier this year so hopefully it’ll be better than previous years. My fan is on the outside so I have ducting in the tent, pulling the air out and pushing it through a filter, then into the open shed. Does that change anything? I figure in venting the air right back into the environment. Does that even make sense? I figure it will at least pull the moist air that’s accumulated in the tent, and hopefully it gets taken care of by the dehumidifier.
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Bumping in the hopes that somebody sees the question in my last comment
That solves the humidity but doesn’t get fresh air in. What the plant breathes out should be exhausted and new air in.
As said to replenish co2.
Either venting to, or intake from, outside, will solve that.
Maybe need to crack the door on the shed from time to time
I have all three bottom flaps/vents open at all times with my exhaust fan running at lvl 1 to draw fresh air in.