I am running in my basement since day one… It is a very small room (120 sq ft). My machine is 5′ x 5′. I have 12″ 600 cfm exhaust fan suck crap and fumes out of the room.
Fortunately when I built the room I insulated all the walls and the ceiling as well. So even directly above when the MPCNC is running you can barely here it if its pretty quite in the house. The room is also isolated from the return air ducts so it does not suck in stink when the laser is running.