This study addresses the relevant problem of cleaning industrial gas emissions from oil mists amid tightening environmental regulations and the need for energy-efficient separation devices. The efficiency of a vortex separator of straight-through type with an axial gas flow swirler as a promising design that minimizes secondary liquid carryover through liquid drainage from the blades has been experimentally investigated. The influence of key swirler design parameters (number of blades: 6, 8, 12; inclination angle: 30°, 45°, 60°) and operational characteristics (specific load 0–0.58 kg/kg, gas velocity 15–23 m/s) on the separation process has been determined. The optimal swirler configuration (6 blades at a 45° angle) has been substantiated, providing a compromise between high separation efficiency at moderate loads and low hydraulic resistance. A comparative analysis with a hollow vortex apparatus and a vortex chamber confirmed the universality of the identified patterns and demonstrated the advantage of the separator with liquid drainage in the moderate load range (L/G < 1.5). Practical recommendations have been developed for the design and operation of vortex separators aimed at improving air quality in industrial zones and reducing environmental risks.