Blessing with fresh air to breathe is one of the primary living requirements of the Human being. Nowadays, majority of the countries in the world are suffering from the problem of Air pollution. This problem is getting worse day by day because of rapid economic growth, industrialization, urbanization and the resulting rise in energy demand. Air pollution has been become one of the primary concern in Sri Lanka. In most of the Sri Lankan cities, the primary cause for the air pollution is the lack of the prevalence of proper environmental regulations. Although the scientific evaluation of such technologies and systems is generally recognized as a significant facet of open source technologies and their implementation, it is often underexplored in science. This research provides an integrated approach to the development of an Environmental Monitoring System prototype based on open source hardware and software and to track the reliability of the system in terms of data accuracy. This system is able to measure six environmental parameters namely air temperature, air CO Percentage, air NO2 percentage, air O3 percentage, air PM percentage and air SO2 percentage. This research has shown a promising way to create a dense coverage for more cost-effective monitoring of environmental phenomena. Most of the existing monitoring systems for air pollution have inferior accuracy, low sensitivity and require laboratory study. Our implemented system is a three-phase air pollution monitoring system, which have drastically shown improvements over the existing methodologies combining with the Internet of Things (IOT).