I've just built a darkroom, approx 16 x 8 which also houses my office. There are 3 opening windows plus the door (which can all be blacked out) which give me plenty of fresh air. I'm thinking of some form of air purifier to filter out any odours and chemical fumes when using the darkroom, (Ive seen this model but its hideously expensive,,,,Filtaire Air Filter Unit Model 300) or would this be unnecessary given the level of ventilation already there?