When working with open radioactive sources, radioactive gases and aerosols can be released with air exhausts. According to Finnish radiation regulations, the operator is responsible for determining the amount of radioactive discharges and their effects on effective dose of local population. In this study the amount of radioactive discharges in air exhausts of open source laboratory were measured. The measurements were executed by developing a new computation software for the old discharge measurement system used at MAP Medical Technologies Oy (MAP). Obtained results were compared to those provided by newer measurement system used at MAP and discharge limits defined in Annex of this study. Different systems produced very similar results for 131I discharges, but the results for 123I differed by a constant factor. The difference in 123I results was assumed to be due to differences in calibration. The discharges measured during the early 2016 were distinctly lower than the discharge limits.