What is the reason why KTV smells bad? What if you don't need fresh air?

KTV private rooms are closed spaces, and the odor is that the odor generated by customers smoking and eating in the room is absorbed by the wooden decoration of the sofa, and then slowly released. To remove it, first put some green plants in the room (often taken out to bask in the sun), and then put something similar to graphite in the sofa and wooden decoration to absorb the odor.