Fumes welding

Exposures to chemicals may involve solids, liquids, or airborne matter as mists, aerosols, dusts, fumes (i.e. pm-sized particulates), vapours or gases in any combination. Many situations, e.g. exposure to welding fumes or to combustion products from fossil fuels, include mixtures both of chemicals and of physical forms. Quantification of exposure is then difficult. 

Measures to control welding fume include process modifications, engineering controls, system of work and administrative acdon as summarized in Figure 5.5. 

Figure 5.4 Possible constituents in welding fumes and their effects...

VM and P naphtha Warfarin Welding fumes (total particulate) (NOC) F (0.8 pm MCEF) 720 1500 G... 

Fumes are formed when material from a volatilized solid condenses in cool air (e.g., welding fumes). 

The procedures and requirements for rhe type and commissioning tests are covered in narional and international standards—for example, for laboratory fume cupboards, welding fumes, and kirchen hoods. 

Weld fumes The fine fumes that are produced and liberated into the room air during the welding process. 

Separation and detection methods The common methods used to separate the Cr(III)/(VI) species are solvent extraction, chromatography and coprecipitation. In case of Cr(VI) from welding fumes trapped on a filter, a suitable leaching of the Cr(VI) from the sample matrix is needed, without reducing the Cr(VI) species. The most used detection methods for chromium are graphite furnace AAS, chemiluminescence, electrochemical methods, ICP-MS, thermal ionization isotope dilution mass spectrometry and spectrophotometry (Vercoutere and Cornelis 1995)- The separation of the two species is the most delicate part of the procedure. 

There are a number of other elements appearing from time to time in the laboratory. From these, chromium and nickel are most common. Both appear in enhanced concentrations in workers exposed to welding fumes, in galvanization processes, and in processing of ores. Prolonged exposure to Cr and/or Ni causes cancer and affects the kidney. Preferred methods of determination of Ni and Cr in urine are GF-AAS. Because of the risk of contamination of the very low concentrations in urine, extreme precautions in sample handling and analysis must be carried out. 

---