I have a similar setup with my trays.
They drain out of the room and the water collects in totes in my garage.
It doesnt get emptied every night so I added the sm90 to deal with the funk.
The co2 stays in the room despite the drain setup.
Its a good idea to have some sort of catch to monitor the runoff of the individual blumats to dial them in and make sure they stay at the proper moisture level
How do you know besides the plants telling you if more drip is required? Mine seem to drip most all the time now but there is never any runoff. That's why I bumped to 1ml/gal dripclean like a lot of guys do. The thought of unused nutes staying in the roots 24/7 made me do it Not that I know crap about blumats, coco or growing in anything but soil
I set them at clinging drip + 1 arrow more.