ALASCA proficiency testing scheme for occupational hygiene laboratories

Nowadays, quality assurance is an important part in the environment of analytical laboratories, who need to prove their ability to perform analysis as well to handle routine control as research and development analysis. A proficiency testing scheme (PTS) is one of the possible and powerful tools to evaluate both bias and dispersion of the analysis. As far as industrial hygiene is concerned, since analytical uncertainty is insignificant with regard to sampling strategy uncertainty, laboratories could be tempted to neglect analytical uncertainty assessment as well. The department 'Métrologie des Polluants' (part of INRS) has been organising a proficiency testing scheme since 2002 with the intention of giving the most reliable performance assessment to the participant. The original features, which are also the strong points of the scheme, are: the determination of the assigned value by a method that is independent from the analytical method to be tested; the development of original tools for the fabrication of samples; the strength of the statistic model, which is based on the WASP HSL scheme model; a tool to visualize the results of participants in bias and dispersion contribution; communication with the participants; a completely computerized system to handle the participant database, the sample database, results treatment and report edition; and the use of internet facilities to allow the participant to submit the results via a secured website. All these technical and organisational points are detailed in this paper.