Dry scrubber systems spray a collection of dry reagents into the exhaust. These reagents can have a number of different effects depending on the material they target. Some will simply neutralize a harmful material through a chemical reaction.Others cause a material to react and accrete into a different substance that is large enough to fall out of the gas stream or be caught in a particle screen. Since the vapor in these gasses is very low, they are typically dark or invisible when vented.