In this study experiments were carried out by generating Sodium compound aerosols in the aerosol test facility (ATF) and exposing the chamber volume panoramically with gamma radiation source. By using it light scattering technique, the real time changes in number concentration of aerosols and their volume-size distributions were measured. From the data, the cogulation coefficient is derived with and without the presence of gamma radiation field. It is observed that the coagulation coefficient is nearly one order more in the presence of gamma field than without gamma field. From the volume-size distribution data, it is observed that when there is no gamma field, there is a gradual shifting of mode from lower size to upper size ranges during the period of 100 min whereas, when gamma field is present, the size distribution becomes bi-modal at about 5 min duration and becomes multimodal as time progresses. (C) 2008 Elsevier Ltd. All rights reserved.