Quitters will constantly spit black phlegm for about 20-40 days after quitting smoking, and the phlegm will basically be expelled after 40 days after quitting. Because in the process of quitting smoking, phlegm from the respiratory tract will produce mucus that will wrap the deposited substances of dust and tobacco inhaled from the airway, and constantly expel the substances through the peristalsis of airway cilia. The main mixture of nicotine and tar, so there can be a black phlegm, which is very good for patients who quit smoking and is good for the health of the lungs.