Radon is nowadays used as a tracer for atmospheric transport model validation because of its physical and chemical characteristics. 222Rn source term characterization becomes necessary for more accurate validations into the current non-stopping progression of atmospheric dispersion model development. Direct measurements of radon exhalation flux density are carried out in order to obtain a reliable map with required spatial and temporal resolutions. To measure radon exhalation flux density, the INTE (UPC) institute uses an integrated electret ionization chamber (EIC) system, also known as electret radon flux monitors. Different configurations of this device have been developed by the manufacturer and used in a comparison campaign held in the summer of 2008. In the comparison campaign, of radon exhalation flux density, measurement was carried out at four locations of the eastern Spain. The electret radon flux monitors response in different soils and with different environmental conditions was analyzed. The different electret radon flux monitor chambers show coherent results in comparison to the other integrated and continuous radon flux systems which also participated in the campaign.