A Dynamic Trace Voc Generator Useful for Global Climate Change Study

With the goal of the realization of a primary standard of amount-of-substance fraction of VOC (Volatile Organic Compounds) at trace level, a dynamic generator is constructed, based on the diffusion phenomena, according to ISO 6145-8. Generator will be followed by a dilution system. In the present paper, generator performances are discussed. The analysis of ISO 6145-8 shows that temperature control gives the main contribution to uncertainty. The use of a more precise temperature and evaporated VOC mass results to be the main contribution. Weekly measurements of diffusion rate demonstrate the correct uncertainty calculation and the enhances due to the more precise temperature control. Uncertainty of diffusion rate was calculated as composed uncertainty of measured variables to be 0,4% for 20 μg/min by weekly measurements instead 0.8% calculated for the ISO 6145-8 conditions. Type A calculation of uncertainty on experimental data, corrected by pressure, confirmed theoretical uncertainty calculation.