Fresh air it important for health, specially indoors. Lots of buildings got this special sistem called fresh air return sistem. This help bring in new air while push out the stale one. It like breathing for house or office. When we breath fresh air, it keep us alert and feel better. Without it, inside air get dirty full of dust, smoke, other bad things. Liba get how crucial this are and they help make sure building have right sistem for clean fresh air.
A fresh air return sistem is part of building heating cooling setup. It pull air from outside and mix it with inside air. Then push out old stale or dirty air. This process keep indoor air fresh. Think it like open window but no noise or bugs.