The vortex tube uses energy separation technology to separate inlet gases into hotter and colder mixtures than the inlet state. In this research, a feasibility study is carried out on a vortex tube used to separate CO2 gas from air-CO2 gas mixture at atmospheric temperature. Prior to the feasibility experiment, transient response of vortex tube is investigated to determine the time needed to achieve steady state temperature of energy separation. The experimental parameters of gas separation are the pressures and concentrations of CO2 that is mixed with air. Results show that CO2 gas separation is proportional to operating pressure. The results also show that the cold mass fraction is a core parameter for gas separation. The percentage mass fraction of separated CO2 gas at cold exit is 7.4% at 3 bar(g) and cold mass fraction of 0.6. (C) 2018 Elsevier Ltd. All rights reserved.