Document jBBoQm41137nL2ggzEqq8g3kk

12 ,'Sth Xational Safety Congress, 1947 will be .the exposure. With the higherjem* perature the metai is more readily oxidized to produce a druss consisting of a high j>crceniage of lead oxide. The dross may provide a protectee coating to reduce the volatilization of the lead: however, disturbance of this coat* mg will create an exposure. As a safeguard against excessive umtamiruiion. pots contain* ins solder or babbitt are usually ventilated. Wherever possible it is advisable to enclose the pot as completely as possible and provide sufficient air volume to overcome the thermal effects of the molten metal. Attempt* have been made to use natural draft ventilation systems to cnntrol these func ami in those instances where (he duct* were not of suffi* cient diameter the system was inadequate A preferable method i* the u*c of mechanical systems. The removal of excess voider with power driven tools, such as grinding wheels, diso. or wire wheels, creates airborne dust which may contaminate large areas of the factory if the operation is extensive. Diligem use of abrasive cloth will also result in excesivc concentrations of lead dust. Filing, however, is not productive of small particles and is preferred over the u*c of power driven tools. If filing i* not practioble or feasible it will be necessary n* provide wmc type of me* chanical ventilation system for the solder re moval operation* involving the use of power tools. Since the permissible limit generally accepted for lead is 1.5 milligrams per to cubic meters of air (355 cubic feet) it will be nccewarv to have an effective system to pro vide adequate control. F.nginecn experienced in designing ventilation systems to control toxic material* should be consulted, other wise a comIv sv'vtcm might l>e erected and later discovered to l>e entirely ineffective. Fre quently solder removal operations require (he use of portable tools on Urge objects and a local exhaust system would not be effective, a* is the case in the fabrication of automobile bodies. General contamination of the factory* with lead dust has been eliminated by enclos ing the entire operation in a large booth and exhausting a sufficient quantity of air from the enclosure to insure a constant inward flow of air from (he factory into (he booth. Under these circumstances no practical amount of air. could be removed from the booth to reduce the lead concentration to a safe level, and therefore it is necessary that the men working therein be provided with adequate personal protective devices. HeatTrrating-High temperatures aie a frequent source' of "complaint"from'entployees m heat treat departments but such condi tions and their control are not wuhin the subject matter under discussion. Fumes disseminated from cyanide jots are often associated with cyanides used as fumi gants or as the lethal agent in death cham bers and supervision as well as the employee becomes apprehensive. Fumes from such a source are irritating and bcause of this property should be adequately ventilated. The irritant nature of the fume Is caused by alkali formed upon decomposition of the cyanide. Molten lead is sometimes used as a harden ing medium for metals. Frequently charcoal or some similar material is placed on the surface of the meal to conserve heat and prevent oxidation. A covering of thk type reduces the volatilization of lead while the bath is quiescent, but has no effect while the, bach is in use. Adequate vemihtion should* therefore be provided for baths of this type. .As complete an enclosure as ts practical for the operation being performed b advisable with air quantities dependent upon the open areas in the hood. To prevent contamination resulting from rolatiUadon of lead accumu lating in the combustion chambers the prod ucts of oombustion from gas fired lead poc* should be vented to the outdoors and not be allowed to dissipate into the workroom. Iron Foundries--Tbe principal ingredient* of foundry dusts are lilio, tea coal, clays, and parting compounds. The predominant ma terial will be dependent upon which phase of the foundry operation is being studied and what operation is being performed. Tbe control of dust is the major problem, whereas fume is of secondary importance. A discussion of all the aspects of the in dustrial hygiene problems in such plants would require a separate treatise. For the present discussion it should be sufficient to state that all obvious sources of dust dis persion should be reduced to a minimum by adequate localized exhaust svucrav In a mechanized foundry such places would be sand conditioning and miking equipment, tumbling mills, shakeouts, core removal and knockout stations, transfer points of . dry sand, abrasive blasting operations, and all grinding operations performed on castings containing appreciable quantities of sand.