The digits can be found in the taller potted plants, trash cans and the computers. On the computers, the apps are clickable, and sometimes part of the codes are in there.
The red/green things on the wall control the ventilation, green means it's on in that room, red means off. If the ventilation annoys you, you can turn it off, but it differs by room, and if even 1 room is on, then the ventilation stays on.