Air quality is a major social issue. Among the many compounds that could be harmful for Human health, Volatile Organic Compounds (VOCs) belong to the most monitored and regulated pollutants. In France, the monitoring of VOCs in ambient air is carried out by sampling air onto activated carbon cartridges during a given period (7 or 14 days) by the "Associations Agréées de Surveillance de la Qualité de l'Air" (AASQA). This method consists of two parts: sampling and analysis. To ensure the reliability of their measurement results, laboratories must guarantee the traceability of their analysis and validate their analytical protocols: this can be done by the use of Certified matrix Reference Materials (CRMs). However, in France, no reference materials are available for the measurement of VOCs in air onto sorbent tubes. Therefore, LNE developed a system for loading benzene, from a gaseous reference material onto Carbopack X tubes. These CRMs could be used for the calibration of analytical systems and for the evaluation of analytical laboratories. After this development phase, LNE has organized a proficiency testing between three expert laboratories, based on the implementation of these materials: it shows no significant differences between analyzed masses and loaded masses for each participating laboratories.