The principal function of Plant 2/3 was uranium purification and conversion of uranium bearing materials into uranium trioxide (UO3), or orange oxide. There are three principal forms of uranium residues, each having a separate processing route for putting the uranium into solution. Uranium oxides are dissolved in 6000 gallon vats of pure nitric acid in the Oxide Digester (also known as the west metal dissolver), miscellaneous residues that required filtration were dissolved in the Slag Leach Digester, and metals were dissolved in the Metal Dissolver. If the ore was poured too rapidly into the nitric acid vats a condition known as a "boilover" results. The reaction generates so much gas that it becomes a foam and boils over the sides of the vat. Many workers were told to not step in any puddles on the floor as they were probably nitric acid left from one of these "boilover" incidents. The site employed their own cobblers just to repair work boots that had been exposed to too much acid. Another hazard was the nitrogen dioxide fumes coming off the nitric acid vats. There were so many fumes that on high humidity days during the summer there appeared to be an orange cloud encasing this building and anyone just walking past would experience a sensation as if he had wandered into a swarm of bees.