How to determine the extent of the hazards of dust
To determine the extent of exposure to a productive dust hazard, a comprehensive and comprehensive analysis is required. First of all, should determine the degree of harm to the qualitative indicators, that is, the production of free silica in the dust content. Second, the quantitative assessment of the degree of harm to the quantitative indicators, that is, workers exposed to the total lung ventilation time and the production of dust concentration exceeding the standard multiple. The standard will be the production of dust hazards are divided into five levels: 0, I, II, III, Ⅳ level hazards. To determine the degree of harm, as long as the site obtained by the three indicators of data in the hazard level table to find the appropriate location, you can find out the level of the hazard rating table.
(1) The content of free silica in productive dust refers to the percentage by mass of crystalline free silicon dioxide in the productive dust. The level of its occurrence and development of silicosis plays an important role. The standard will be divided into four categories: that is equal to or less than 10% of the free silica dust; content of 10% to 40% of the free silica dust; content of 40% to 70% free silica dust , And greater than 70% free silica dust.
(2) Workers exposed to dust The total lung ventilation refers to the workers in a working day of the dust-absorbing time with the production of dust in the total volume of air. In contact with the same nature of the productive dust industry, because the workers in the production conditions are different. Labor intensity and duration of exposure to dust vary greatly, so the actual inhalation of the dust in the lung is also different. Taking into account the complexity of China's production methods, the workers exposed to the time the total lung ventilation as a quantitative index, included in the grading standards. Workers exposed to the time the total lung ventilation, including the actual content of the two, namely, workers exposed to dust investigation, as well as the time to catch the lung total ventilation measurement. This indicator not only shows the size of the labor intensity of workers, but also reflect the actual workers exposed to dust time.
(3) production of dust concentration exceeding the standard multiple, refers to the actual measurement of dust concentration in the workplace, more than the national standard multiple, the calculation is as follows:
Productive dust concentration exceeding the standard = dust measured value / the maximum allowable concentration of dust
Then, take several times the measured concentration of dust exceeded the arithmetic mean of multiples.
For example, the content of free silica is 99.50% when the natural sand used in a casting clean-up post is used. A working day in a lung total air volume of 6999 liters / day, the dust concentration in the workplace is 4 mg / cubic meter, the national standard provides the maximum allowable concentration is 1 mg / cubic meter, according to the calculation, exceeding the multiple of 3 , In Table 3-2 to find the appropriate location to identify the level of dust hazards for the job level Ⅲ.
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