The air tubes in the lungs have many tiny hairs which clear the tubes of dust and germs. Cigarette smoke stops these hairs from working. Therefore, dust and germs enter the lungs easily. The lungs then produce a lot of mucus or phlegm which causes the smoker to cough continually. The air passages also become swollen and inflamed, and the person then has bronchitis. A person with bronchitis has difficulty in breathing and may not able to walk properly. Bronchitis can kill if it lasts for a long time.