I don't know about steam however I had an icicles form from my room which completed disabled the night vision of that one camera. The ir reflected back, icicle was bright white but the yard was totally dark otherwise. Other cameras work great and very clear. I would be leery that thick steam would have a similar effect in darkness. As for fogging, these cameras have great resolution and I would imagine placement would make a huge difference, you should be able to put them far enough away not to fog and still have a clear view of what you are trying to monitor.