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In this paper, we designed, simulated and analyzed a non-dispersive infrared gas sensor which can replace gas sensors of the catalytic combustion, electromechanical and semiconductor types. We also proposed commercial sensors to be used in fields of the gas industry. The proposed non-dispersive infrared gas sensor is structured with three ellipsoidal waveguides. Three waveguides share one light source. A non-dispersive infrared sensor is equipped at the end of each waveguide. We designed the proposed CO2 sensor with three waveguides, verified its sensor by using a 3D modeling program (Solid-works), and manufactured its sensor. To simulate its sensor, we supplied power to the light source and measured the maximum emitting energy at absorption wavelength bands of the ethanol and carbon dioxide. Energy absorbed by the gas sensors mounted on the end of the three elliptical waveguides was calculated by a computer simulation program (Trace-Pro). As the results, every power absorbed by three sensors was about 1% of power supplied to a light source. Gas concentration can be measured at three sensors applied 1% of original power. Other two waveguides was 65% of the peak energy of a center waveguides. Experiment is performed that concentration is measured with output voltage of proposed sensor while standard carbon dioxide gases with 6 type CO2 concentrations are slowly injected into a closed chamber. It is derived of the calibration equation using the result of experiments and compared output characteristics of the proposed sensor with a manufactured sensor. It is verified that errors are ±16% at 0~500 ppm and ±4% at 500~ 2000 ppm. When the maximum and minimum values were excluded, the error is estimated to less than ± 1.5% at 100~2000ppm. It is showed the proposed optical CO2 sensor is similar to performance of commercial gas sensor.