用二阶段抽样方法对淄川区１４５个单位进行粉尘作业卫生学调查。结果表明企业进行粉尘自测率低，仅为５５％；作业点粉尘浓度合格率仅为２２６％；粉尘中游离二氧化硅含量与５０年代同行业相比有较大幅度下降 Two - stage Sampling Method for Zichuan District, 145 units of dust hygiene survey. The results showed that the self-testing rate of dust was only 55%, while the passing rate of dust concentration was only 226% at the working point. The content of free silica in dust was significantly lower than that of the same industry in the 1950s