Scintillation cells are used in continuous mode for thoron estimation using gross alpha counts. Such methods give rise to overestimation resulting from buildup of background counts due to the deposition of Lead (²¹²Pb). Here, the background counts in the cell for a specific counting period owing to previously deposited ²¹²Pb has been estimated using a model to get a time dependent correction factor. This correction for ²¹²Pb deposition has been utilized to estimate the current thoron concentration of the sample. The concentration obtained by this method is validated using the scintillation cell by grab sampling method and a continuous thoron monitor, RAD7.