greetings!

an above-ground door opens to a stairwell, more than 20 steps down, which reaches another door that enters into a room. in this room, we are looking to set up some grow shelves! i have lots of experience with growing in closets, but these have always been in rooms that have windows and nice ventilation that i can open the closet door up to. i have always, however, added a fan into the closet for circulation, and thus prevented plant mildew or disease caused by lack of circulation and also strengthening young plant stems...and so i plan to add series of fans to circulate air about the grow room.

my outreach is for, considerations or relations of experience concerning the lack of fresh air ventilation in an underground/sealed room where moisture is being created, for the above-ground door is kept locked most of the time, thus blocking the fresh air-in source. reflections, suggestions, ideas, thank you.