Energy losses through ducts are crucial regarding building efficiency. There are two main ways of these losses: air leakage and by conduction. Typical systems lose 25% to 40% of the energy passes through them. The duct efficiency varies from area to another. Chicago as an example of cold area has 63% for heating and 83% for cooling while Orlando/ Florida which is in hot climate has 74% for heating and 65% for cooling. Most of the duct are located in spaces that are not heated or cooled that result in a significant amount of energy losses when the air passes through there spaces. The duct system affects the equipment efficiency so when the losses through the ducts are high, the equipment is overloaded and make them running at low capacity. In order to achieve a high performance of the duct system of an existing building, an evaluation should be made by inspecting the duct if there is any leaking or un-insulated ductwork. Then the ducts system should be repaired and sealed. In the traditional duct sealing method, the workers need to find leaks manually and then seal them one by one, for this reason it was important to find more effective way for sealing the ducts. Aerosol sealing method require to seal the grills of the cooling/ heating system attaching the duct sealing device to single point and measuring the leakage before and after blowing sealant into the system.