@sueinmn You are very knowledgeable and logical thinking. I do find I have darker sputum EACH time I did highly intensive exercise like a lot of push ups. My pulmonologist suggested me to hold airway clearance to see whether it can resolve the bleeding. In addition, I used two vials of saline for airway clearance each time, totally four vials a day. I am not sure whether it irritates my lungs too. Probably I should hold for both - exercise and airway clearance.