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HighlightsInduction charging of water droplets by an ESS showed greatest CMRs using an 80° tapered edge flat spray nozzleCMR of 0.578 mC kg-1 achieved with a water mass flow rate of 0.397 kg min-1 and an applied voltage of -11.6 kVChanges in water conductivity did not significantly affect measured droplet CMRsAbstract. Particulate matter (PM) is a prominent air pollutant in poultry facilities. One promising technology for PM mitigation in poultry facilities is the electrostatic spray scrubber (ESS). However, there is a significant lack of information on the charging characteristics of an ESS to promote efficient droplet charging and poultry PM collection. This study quantified the effects of applied voltage, water mass flow rate, water conductivity, and spray pattern on the charge-to-mass ratio (CMR) of droplets charged by a ring-shape electrode during induction. Voltages from -5 to -14 kV were applied to a 100 mm diameter, cylindrical copper electrode ring to charge droplets sprayed from different nozzles using 80° hollow cone, 80° tapered edge flat, and 110° tapered edge flat spray patterns. It was found that CMRs increased with greater negative voltages up to a point, after which greater negative voltages would decrease the CMR. A similar trend was observed for the effects of water mass flow rate on CMR. Water conductivity showed inconsistent effects on CMR across spray patterns and was deemed a statistically significant but practically insignificant factor. The 80° tapered edge flat spray pattern was found to produce the greatest CMRs. A linear regression model (R2 = 0.865) was developed and optimized to find the ESS configuration resulting in the greatest droplet CMR. The optimal CMR was 0.578 mC kg-1, produced using an 80° tapered edge flat spray nozzle at a water mass flow rate of 0.397 kg min-1, a conductivity of 0.05 S m-1, and an applied voltage of -11.6 kV. Keywords: Droplet charging, Electrostatic scrubber, Electrostatic sprayer, ESS, Induction charging, Spray charging, Spray nozzle.