In this work, the effect of the atmospheric humidity on the electrical conductivity of oil as well as its implications in the case of electrostatic atomizers are studied. It was observed that the electrical current through oil increased by at least two orders of magnitude when the relative humidity changed from similar to 10% to similar to 85%. A comparison of these results is made with the available model for the electrical conductivity of organic liquids. Additional experiments with oil previously subjected to elevated relative humidity were conducted to evaluate its performance in electrostatic atomizer. No improvement of electrostatic atomization was detected, rather a detrimental effect to the steady operation was introduced.