NAC is a great supplement. It's awesome stuff to support healthy lungs. NAC is a known mucolytic. That is a fancy term meaning breaking up mucus. Now, research does show that NAC Glutathione S transferase omega in the lung and sputum supernatants of COPD patients Respiratory Research Springer Nature Link Lung glutathione and oxidative stress: implications in cigarette smoke induced airway disease American Journal of Physiology Lung Cellular and Molecular Physiology American Physiological Society Met Tathione