5. To avoid dust, ores intended for charging distillation furnaces shall not be stacked in front of or charged into the furnace, or mixed with other material, except in a damp condition.
This regulation shall not apply to large so-called Silesian
Retorts when in use in the zinc smelter; yet in the case of them also the Higher Authorities may require damping of the charging material if specially injurious to health.
6. Dust, gases and vapours escaping from distillation furnaces shall be caught as near as possible to the point of origin by efficient arrangements and carried out of the smelting rooms. The entrance of the gases from the fires into the smelting room shall be prevented as far as possible by suitable arrangements for drawing them off.
7. Residues shall not be drawn into the smelting room; they shall be caught in closed channels under the furnaces and emptied from these channels at once into waggons placed in passages beneath the distillation rooms.
This regulation (where the Higher Authorities approve) shall not apply to existing plants, should it be impossible to make the arrangements mentioned in Reg. 1, or where such additions could only be added by rebuilding at a prohibitive cost.
8. Sieving and packing of by-products obtained by the distillation of zinc (poussière, flue dust) shall not be done except in a special room separate from other workrooms, in accordance with Reg. 1.
Sieving shall only be done in an apparatus so arranged as to prevent escape of dust.
In brass casting, in order to prevent occurrence of brass-founders’ ague, it is necessary that the zinc oxide fumes evolved should be effectively drawn away from the crucible by locally applied exhaust ventilation. General ventilation merely of the room is almost useless, as in casting the fumes rise up into the face of the pourer. Seeing that casting is carried on in different parts of the foundry, it is advisable to connect up the hoods over the moulds by means of metal piping with the exhaust system, or to arrange a flexible duct which can be moved about as occasion requires.
Dangerous acid fumes (notably nitrous fumes) are evolved in metal pickling, especially of brass articles (such as harness furniture, lamp fittings, church utensils, &c.), for the purpose of giving them a shiny or dull surface by immersion in baths of nitric, hydrochloric, or sulphuric acid. As severe and even fatal poisoning has occurred in these operations they should be conducted in isolated compartments or channels under exhaust ventilation. If the ventilation provided is mechanical an acid proof earthenware fan or an injector is necessary. The following description applies to one large works: The pickling troughs are placed in a wooden compartment closed in except for a small opening in front. To this compartment a stoneware pipe leading to a stoneware fan is connected. The nitrous fumes are drawn through the pipe and led into the lower part of an absorption tower filled with cone-shaped packing material through which water trickles from a vessel placed at the top. The greater part of the acid fumes are absorbed as they pass upwards and the water collects in a receiver below, from which it is blown by compressed air into the vessel above for utilisation again until it becomes so charged with acid that it can be used for pickling purposes.