Air pollution is one of the pollutions that basically a mixture of various dangerous particles and toxic gases in the environment, its affect the human respiratory system. The level of pollution has increased with times by numerous reasons, like the increase in population, increased vehicle use, industrialization and urbanization. These variables have a negative impact on human welfare by directly impacting the health of those who are exposed to it. To keep an eye on in this research a prototype IoT based Air Pollution Monitoring System has been developed which will monitor and measured the concentrations of main air pollutant gases like CO2, smoke, benzene, LPG gas, CH4, CO, SO₂ and NO₂. It also measured the humidity and temperature with air quality. This research involved hardware development in which hardware development includes the Arduino UNO, several gas sensors (MQ-2, MQ-4, MQ-7, MQ-135), Humidity and temperature sensor AM2302/DHT22, a buzzer, Bluetooth (HC-06) and LCD display. Sensors used in the presented work have been interfaced to their respective board in order to perform detection of various parameters in real time and obtain detection results simultaneously. It can monitor the pollution level and current reading can be viewed from anywhere using computer or mobile by Blue serial beta app. The collected data was compared with standard atmospheric value of different toxic gas level. Data was gathered from Construction site, Steel Industry, Garments industry (Indoor) and metal cutting sites near by Dhaka city in Bangladesh.