Abstract-This paper presents a portable and patient independent respiratory CO 2 monitoring device for early screening of asthma. The device is developed incorporation of hardware (Sprint IR CO 2 sensor with a sampling rate of 20 Hz, face mask, Atmega 328 microcontroller and graphical liquid crystal display-GLCD) and software (Arduino integrated development environment). The Transistor-Transistor Logic (TTL) communication was used to transmit and receive the signal from the host (microcontroller) to sensor and vice versa. Further, the computation and transmission algorithm was developed to process and display the CO 2 signal on GLCD. In addition, the signal processing techniques were used to discriminate mild stage of asthma and non-asthma condition. In this preliminary study, the developed device was tested on 20 subjects aged between 20 and 25 years. Out of those, 5 were suffering from mild asthma and 15 were without asthma. The performance of the developed prototype device was confirmed through statistical analysis using SPSS software which achieved 80% sensitivity and 90% specificity. The p-value of the developed device was 0.000. The result shows that it's statistically significant and able to differentiate asthma (mild) and non-asthma. However, the device will be tested further on a larger number of populations to generalize the finding.