Calculate the size of your grow space, how many cubic feet is it? You want to exchange the air in the room once per minute, some say more some say less. If you have a 40 cubic foot room you need a fan that can exchange the air once a minute that would be 40 cfm. People use inline fans for closet grows and room grows and cabiet grows but for cabinet grows some use other options. So you get an inline fan and have it exhausting the air out of the room and have a passive intake which is basically a hole somewhere that allows fresh air into the room, filter the intake to reduce bugs and pathogens.
This will achieve proper constant fresh air exiting and entering the room which is very important for the reasons others stated above. Also, even with one plant flowering smell will be an issue. Having proper ventilation especially with the aid of a carbon scrubber will eliminate smell and provide fresh air. Then you get a few small fans to blow air inside the room to disperse heat and strengthen your plants.
