All I know is that if there is an inversion layer between your aircraft and them, they don't affect you. At least that was my experience when training in a glider a couple years back. One day we were towed up through some bumpy air to find smooth air above about 1300 ft AGL. After release it was a boring sled ride down - zilch lift anywhere. But dust devils were appearing in spots, so we flew over a couple of them thinking we'd find rising air. Nope - dead still air. The yucky haze layer was pretty distinct, so if something had managed to rise up out of it I suppose we probably would have noticed those areas as "hills of haze."
