Carbon Dioxide (CO2) is an inevitable part in atmosphere for the existence of life on the Earth. But if increased beyond a certain limit it is harmful as it is the major cause for global warming. The only effective way to fight this is to store CO2 away from the atmosphere for a long time. This is achieved by using Carbon Dioxide Capture and Storage (CCS). But one major concern that arises when CO2 is stored in large quantities is it’s leakage from reservoir. An online CO2 emission monitoring and alert system is developed in order to monitor the leakage of CO2 in real time in CCS, try to reduce the leakage up to a controllable level and to give alert to the consent person, if the CO2 leakage goes beyond an uncontrollable limit. The data is stored in real time for further analysis. Advantages of wireless sensor networks are exploited in order to precisely sense the CO2 concentration.