44 MUST - A user-friendly tool for the calculation of measurement uncertainty for methods of workplace exposure

What is measurement uncertainty? Why does it need to be calculated for measurement methods of workplace exposure/ workplace air? How is the expanded measurement uncertainty calculated for these methods? These questions are an important part of the quality assurance for each method validation. The “Guide to the Expression of Uncertainty in Measurement” (GUM) has basically laid the foundations for uncertainty calculation but the application of these mathematical methods is often obstructed my misunderstandings and various interpretations in several standards. The chemical laboratories at the Institute for Occupational Safety and Health in Germany have targeted to solve the misunderstandings and create a mathematical framework for different measurement methods to achieve a situation, where the declaration of uncertainty is a real benefit: one can show compliance, improve the methods, and rely on results based on quantitative data. For this purpose firstly influence factors on the result of a measurement, their systematic and random effects, as well as their sensitivity coefficients must be determined for both: sampling and analytical methods. In a next step a mathematical model must be created. Models for three different measurement methods of air monitoring (sampling with subsequent thermodesorption, extraction methods or metals in inhalable or respirable dust fractions) were calculated and are now conveniently dealt with in the background of a user-friendly open-source software. With this software the expanded measurement uncertainty can be calculated for various concentrations and it can be determined how strongly the individual effects of influence factors are involved.