What is AC Gas Filling? Air conditioners work using refrigerant gas that helps absorb indoor heat and provide cool air. Over time, due to leakage or continuous usage, AC gas levels may reduce, affecting cooling efficiency. AC gas filling is the process of: Checking refrigerant levels Detecting gas leakage Refilling refrigerant gas Restoring cooling performance Without proper gas pressure, the AC compressor works harder, increasing electricity consumption and reducing machine life.