Summary The Québec prevention network, made up of the CSST, health and social services agencies, local community service centres and their points of service, as well as joint-sector based associations, consists of several hundred people working in occupational health. In the context of their mandates, they perform interventions in companies in order to collect samples for air quality evaluation. These samples are analyzed in a centralized way in the IRSST's laboratories.The results of the air samples collected for the years 2001 to 2008 have already been the subject of an annual analysis, and the reports produced have identified several situations of high concentrations in the two-digit large industrial groups of the Classification des Activités Économiques du Québec (Québec economic activity classification, CAEQ, 1984). This report groups, in one place, all the results of the environmental analyses issued by the IRSST laboratories for this entire period. Considering the important volume (359,120) of results produced during this period, it becomes very interesting to process the data in such a way as to produce a detailed portrait of the pollutant concentrations by the four-digit industrial classes of the CAEQ rather than by large groups. This choice should in fact allow a more detailed reading of the analytical results and therefore a more directed focus on the evaluated exposure situations where the chemical substances considered individually are found at considerable concentrations in establishments. In order to present the same reality from different standpoints and facilitate the understanding of the results in relation to the preventionists' specific interests, the results are presented according to the CAEQ industrial classes, by CSST priority sector, and by substance. The study was carried out to provide researchers and preventionists with information that can support new research orientations and help in the prioritization of certain interventions.Only the most relevant results with respect to the study's objective are presented. Hence, some 68, 342 analytical results meet the extraction criteria and identify the chemical substance-industrial class combinations most likely to be problematic among the sampled sectors. Their examination differentiates 56 chemical substances among 183 industrial classes and identifies a total of 483 chemical substance-industrial class combinations that were the subject of at least 25 analyses during the 2001-2008 period, and for which at least 20% of the analytical results equalled or exceeded 50% of the standard. These data, presented in six appendices, show the great diversity of samples for which a proportion of the analytical results were of higher concentration.Among the exposure results, several situations seem particularly problematic.Beryllium in the Industrial Organic Chemical Industries, lead in Large Industrial Structures, aluminum in Other Utilities, manganese in Other Material and Waste Salvaging, dusts not otherwise classified in the Clay Products Industry (Canadian clay), wood dust in Forestry, asbestos in Other Machinery and Equipment Industries, nicotine in Correctional Services, and the mixture of triglycidyl isocyanurate isomers in the Custom Coating of Metal Products Industry are just a few examples of situations where more than 60% of the samples collected were above twice the standard.