Surging of a compressor occurs when the airflow through the compressor becomes unstable, leading to fluctuations in pressure and flow rate. This instability can cause disruptive noise, vibration, and potential damage to the compressor components. Surging typically happens when the compressor operates at flow rates lower than its design capacity, leading to a reversal of airflow direction within the compressor. It is essential to prevent surging through proper compressor sizing, control strategies, and maintenance to ensure the reliable operation of the AHP.