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Tham khảo tài liệu 'health safety and environment_3', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 7.4 Emission of Dust 309 blast cleaning method Fig. 7.12 Exceeding of critical dust concentrations for different blast cleaning variations Plitzko et al. 1998 relative dust concentration Fig. 7.13 Effects of ventilation on dust concentration Mickelsen and Johnston 1995 310 7 Health Safety and Environment Fig. 7.14 Relationships between air supply to helmet helmet screen design and dust concentration in helmets Greenburg and Winslow 1932 An extensive database on site measurements of the exposure of workers to total dust respirable dust total crystalline silica and respirable crystalline silica can be found in Heitbrink s 1999 report. 7.5 Emission of Airborne Metals 7.5.1 Airborne Lead Because many old coatings contain lead there is a critical situation as the lead may enrich the operator s blood due to breathing the aerosol. There are the following two critical levels Action Level OSHA AL 30 J.g m3 If an operator works in an area at or above that level the employer must give medical surveillance and training in the hazards of working with lead. Permissible Exposure Limit OSHA PEL 50 j.g m3 This limit is for the average amount of lead in the air over an 8-h day. Extensive studies have shown that airborne lead concentration does not depend on the main lead concentration in coating systems to be removed NIOSH 1997 the correlation between these parameters is very weak correlation 0.22 . It is therefore the surface preparation method that determines airborne lead. Salome 7.5 Emission of Airborne Metals 311 Fig. 7.15 Relationship between lead content in paint and airborne lead exposure for different abrasive materials Salome and Morris 1996 and Morris 1996 have shown that the lead content also affected the amount of atmospheric lead exposure during blast cleaning. Some of their results are plotted in Fig. 7.15. A linear correlation with a correlation coefficient of 0.971 was found. Blasters and painters are particularly endangered by lead exposure this was verified by a .
