This paper presents the design of an IoT based air pollution monitoring system to measure carbon dioxide gas, butane gas, humidity and temperature. The hardware consists of MQ-2 gas sensor, ESP8266 Wi-Fi module, DHT22 temperature and humidity sensors. Meanwhile, the software used in this prototype is the Arduino Integrated Development Environment (IDE) written in function C and C++. The monitoring system indicate air quality is below than 100 AQI for safety air quality and more than 200 AQI for hazardous air quality. The green LED illuminated indicates there is no hazardous gas detected. Meantime, when the butane gas or carbon dioxide gas is identified, the red LED is illuminated. All the data are sent through ThingSpeak and Blynk applications. In ThingSpeak and Blynk applications, the data are displayed and updated after detected by the sensors in every 15 seconds and 1 second. In the Blynk application, when the hazardous gas is detected, the Blynk application sends a notification to alert the users immediately.
