The Kodak guide is, I think, aimed at commercial darkrooms with multiple occupancy, and whilst very useful, the recommendations are a bit over the top for a domestic unit. We need a good fresh air supply and a ventilation system that will take any fumes away from us. One 6" extract fan will do this with capacity to spare in all but the largest room, provided it is on the other side of whatever nasties you are using, and your working position. The air inlet must be adequate, and preferably behind you. If you can arrange to pull your make-up air from the house, then heating, or cooling will not be a problem.
Originally Posted by DKT