Yeah, that would make sense I think, thanks.

All, I checked with a sheet of paper, and there's no draft either way when the furnace is on. Meanwhile it's clearly sucking air at the big return (not pictured), and pushing at all the registers. Maybe this in-wall thing was capped off at some point!?

Hm, good point. I have a much larger return inlet in the hallway, but I'll check tomorrow if I have suction at that duct as well. Is it normal to have more than 1 inlet? I certainly have better things to do if it's not needed.

For instance this duct plus elbow https://www.supplyhouse.com/Lambro-Industries-1020L-3-1-4-x-10-90-Galvanized-Elbow

https://www.supplyhouse.com/Lambro-Industries-126L-3-25-x-10-Galvanized-Duct-24-Length

Delete if not allowed. Thx

Not sure why you think so, with a full face mask and cartridges that filter organic vapor and an additional hepa VOC filter on a good air purifier that should be doable?

That being said, if there's no other way I'll vent first, but that would mean taking down a Lot of plastic and then redoing it

Drywall is physically dry, yes, but RH could still be 80-90 I guess?

I want to keep the plastic up for now ideally and use it to catch any overspray, so, I'd like to keep unvented for now. I'm in full face respirator and will have a h13 hepa air purifier to help with fumes etc

Just fyi, we had the popcorn tested, no asbestos.