Abstract : The air-conditioning system is today a worldwide standard equipment in the automotive industry improving not only the thermal comfort but also the safety of passengers. This refrigerant system uses HFC-134a, a hydro-fluorocarbon refrigerant, whose emissions contribute to global warming. Among the mobile air conditioning components, the compressor has been identified as the most leak prone component representing 50 to 60% of the system emissions. The most emissive component of the compressor is the shaft seal that represents up to 50% of the compressor emissions, as demonstrated in this dissertation. The objectives of this thesis are to study the physical principles and to analyze the experimental results of gas emissions in order to contribute to the knowledge of the fundamental mechanisms and the influence parameters of the compressor shaft seal gas emissions. Two original experimental setups have been developed to study the shaft seal gas emissions in standing mode as well as in running mode. The same test benches have also been used to investigate the seal performances during the compressor aging. This new approach has allowed identifying the shaft sealing mechanism at rest and in running mode. Results obtained have been used to demonstrate the relation between the shaft seal emissions and its lubrication regime, as well as the oil transitory effect when the shaft is at rest. This study has also underlined the significant deterioration process of the shaft seal emissions with wear, which explains the high demand of refrigerant for servicing and the increase in the number of system recharges as the vehicle gets old.