Evaluation of Uncertainty in Determining Free Silica in Silica Dust in Air of Workplace by Pyrophosphoric Acid Method

Objective To evaluate the uncertainty of free silica in silica dust in the air of workplace by pyrophosphoric acid method.

Methods Free silica in silica dust was measured by pyrophosphoric acid method according to the Determination of Dust in the Air of Workplace-Part 4: Content of Free Silica in Dust (GBZ/T 192.4-2007). The uncertainty in the process was sourced, quantified, and systematically calculated.

Results With 58.9% of free silica in silica dust by pyrophosphoric acid method, the extended uncertainty was 2.9% (k=2). Post-treatment of digestion u_rel(x)=1.76×10^-2, uniformity of organic materials u_rel(org)=1.61×10^-3, and repeated measurements u_rel(w')=1.77×10^-2 were the key factors influencing the reliability of results by pyrophosphoric acid method.

Conclusion The method is applicable to evaluate the main sources of result error in the uncertainty evaluation of free silica of silica dust in the air of workplace by pyrophosphoric acid method.