A model of gas to liquid mass transfer in a stirred laboratory reactor was developed with the purpose of controlling:mass-transfer limitations in kinetic studies of olefin polymerizations. Renewing the liquid surface is controlling the mass transfer. Generally, two different scales of;eddies can be envisaged to be responsible for the renewal: at low stirring rates, the mean liquid flow is the controlling mechanism; at high stirring rates, small-scale turbulence provides the renewal. The change is at a specified turbulent Reynolds number. The model for the high Reynolds number region is based on an established mass-transfer relationship from the literature. For low Reynolds numbers, a new correlation is developed based on literature studies of the liquid circulation velocity at the gas-liquid interface. The model predictions are compared with experimental data for propene polymerization in decane. It was found that the small-scale turbulence model was most appropriate, and fitted the data within a factor 2. The models are theoretically founded and form a basis for the control of mass-transfer effects in the measurements of kinetic data.