The XC-540 that I run really doesn't seem to put too much odor in the air when I print small decals and stickers, but gets fairly bad when printing wraps (or after about 5-10' of full width printing).
I just mention this because it is in a room that would be much the size of a basement room with similar ventilation (not much).
After reading that article that cdiesel recommended, it made me think of "eco-solvents" a little different. I'd think of it more like I wouldn't inhale exhaust from a normal car, so why would I think inhaling exhaust from a hybrid is ok? (meaning there is still the "bad stuff" there, but just less of it).