In order to reduce tropospheric ozone level, it is necessary to reduce their precursors, including volatile organic compounds (VOC). Currently, CETESB′s mobile sources emissions inventory accounts only VOC emissions occurring in the vehicle operation. To calculate VOC emissions of vehicle powered by gasoline or ethanol during refueling, it is necessary to know the rate of evaporation of these fuels during the process. Knowing these rates, it is possible to calculate the emissions for each fuel and add this value to the previous VOC emissions. The results show that the refueling emission is significant and must be included in the annual inventory of mobile sources of SPMA, as well as it is necessary to carry out researches about refueling of fuels sold in Brazil.