Abstract Electrical charging of non-radioactive aerosols was studied. The mean charge acquired by the poly-dispersed and mono-dispersed aerosols is determined for the two cases, viz. with and without the presence of additional ion pairs generated by gamma radiation. The results are separated accordingly by determining average charge acquired by the aerosols in three generation route (atomization, combustion and vaporization & condensation) and compared with the charge acquired in the presence of gamma radiation field. Using theoretical formulation developed by Clement and Harrison, the mean charge acquired by the aerosols (mono-dispersed) for a given concentration of both aerosols and ion pairs were calculated and compared with that of experimental results. The study is extended to determine the mean charge obtained for the distribution of DOP aerosols (poly-dispersed), by varying number concentration of aerosols and number concentration of ionpairs. It is found that the mean charge acquired by the aerosols increases with increase of ion pair concentration for a given concentration of aerosols.