The influence of relative humidity on charge decay on polystyrene (PS) particles is investigated at room temperature by using Faraday cup and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy. The PS (2.8 ± 0.4 μm in diameter) particles were charged by using an ozone setup. The ozone charging source was from the free O-radicals generated from O 3 dissociation on the surface of the PS particles resulting in carbonyl groups formation. The charge decayed exponentially, and the decay time constants were quantified using Faraday cup for various relative humidity conditions at room temperature. The charge decay due to the interaction of the PS particles with the environment was also investigated using ATR-FTIR, where the C O stretching band at 1745 cm −1 was monitored. The decay of the C O on the PS particles is due to the reaction of the carbonyl groups with the hydronium ions [H 3 O] +. The reaction of C O with [H 3 O] + is responsible for the time dependent charge decay. From both methods, the charge decay exhibited an exponential behavior, where the time decay constants measured from the two methods were in excellent correlation. The decay time constant increased linearly with increasing the RH. A generalized master charge decay curve is established for any PS surfaces (particles/films).

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