Smoking cigarettes has many deadly effects on the human body, primarily on the lungs. Lungs serve as our machine for respiratory exchange between the body and the surroundings. First, the chemicals in the cigarettes prevent the efficient passage of oxygen and carbon dioxide in the lungs. Smoking damages the alveoli sacs making the person breathe harder. Carbon monoxide, a known pollutant, is contained in the cigarettes was found out to be involving in the destruction of alveoli sacs making it less stretchy due to loss of elasticity. Consequently, the concentration of oxygen can decrease and may affect other metabolic activities of the cells of the other organs. Also, the cleaning and repair system of the lungs are also destroyed by the chemicals contained in the cigarette. If that happens, the chemical can penetrate inside the lungs and eventually affecting the other organs and can cause cancer.