Sounds like you dont have an intake vent, Eric. there should be some fresh air exchange going on. Anyway this brings up a good point for building a darkroom-proper venilation. I bought several used muffin fans for $5 at a surplus store. These are quiet and move a high volume of air. I didnt have to make them light-tight because I only print at night. I mounted them to a board and just place them in the window when I work. The window is behind my sink, so the setup is ME-->Sink and fumes-->fans-->outside. This way I never even get a whiff.(posted 8120 days ago)I built a sink from 1/2 inch plywood and drywall screws. I plumbed it similar to the setup shown at darkroomsource, which (in hindsight) isnt the best setup but it works. That setup allows crossover of hot-cold water to the other side, which can happen occasionally if pressure drops. But it all cost less than $100 and was fun to build, and i'm pretty inept at such things. I coated my sink in swimming pool paint.
I bought just about everything else for my darkroom at very reduced prices by being patient and making phone calls. Got my safelights on ebay. Got 4x5 Beseler enlarger, 20x24 dry mount press, electronic timer, for about $125 total from a newspaper that phased out their darkroom. The only thing I spent any real money on was the Rodagon lens