The system was applied in a university classroom environment to measure O\({}_{2}\), CO, CO\({}_{2}\), and NH\({}_{3}\) concentrations. The ME2-O\({}_{2}\), MQ-7, MG-811, and MQ-135 sensors were used to measure O\({}_{2}\), CO\({}_{2}\), CO, and NH\({}_{3}\), respectively. ATMega32 controls all the sensors to transmit the air-quality data to the web server using an ESP8266 module through WLAN and internet connection in an interval of 5 min. The processed air-quality data were visualized graphically on the web pages and an LCD. The sensor node works using an operating voltage of 5 V and consumes power of 3410 mWh in scheduling mode and 8174 mWh in a full-time mode. A study in [30] presents a compact, low-cost indoor air-quality monitoring system. The platform comprises three sensors, a processor, and a transmission module. The sensors are Si7006 for temperature and relative humidity sensing, CCS811 for CO\({}_{2}\) concentration detection, and PMS7003 for particulate matter measurement. The ATSAMD21G18-48 microcontroller was utilized for data acquisition and processing, and ESP8266-12F was used for wireless data transmission to the MQTT protocol-based cloud server (Grafana platform). The node power source is a 5V external power source using a micro-USB cable. The node is implemented in a two-layer PCB board of 57 mm \(\times\) 75 mm. However, a few single-sensor nodes have been developed for CO\({}_{2}\) concentration measurement that meets indoor application requirements. Most of these sensor systems, as mentioned above, are multiparameter air-quality sensor systems. Moreover, IAQ monitoring devices that are available in the market mentioned in [31; 32; 33; 34] also tend to consume relatively high power, are relatively large devices, and are fairly expensive; therefore, they do not meet the requirement for indoor-monitoring applications. The sensor node should have low-power consumption for long-period operation, be easily installed in limited space indoors, and have low-cost development, as well as being easily utilized and accessed. This paper presents a smart wireless CO\({}_{2}\) sensor node to measure and monitor indoor CO\({}_{2}\) concentration levels. The sensor node is integrated with the IoT system to enable real-time, continuous, reliable, and remote indoor CO\({}_{2}\) measurement and monitoring. Furthermore, the acquired CO\({}_{2}\) concentration level data can be applied as a strategic tool to minimize the risk of the indoor SARS-CoV-2 airborne transmission. A low-power algorithm was applied to drive the sensor node working with low-power consumption toward the autonomous sensor node for long-period operation. The node was designed to meet the requirements of indoor air-quality monitoring applications by considering several factors, such as compact size, low cost, and low power, as well as providing real-time, continuous,reliable, and remote measurement. Moreover, the sensor node uses the cloud system for data storage that can be accessed using the IoT system. This strategy is not only for enhancing sensor-node accessibility (anywhere and anytime) but also to reduce the total energy consumption of sensor nodes that cannot be met if data storage is applied using a commercial data logger (hardware). With the low-power feature, the developed sensor node has the potential to integrate with a micro energy harvester element, which provides energy for sensor node power storage recharging.