Second-hand smoke causes 3,000 lung cancer deaths in non-smokers each year. (American Lung Association)

• Within 20 minutes: Your blood pressure and pulse rate drop to normal. Body temperature of hands and feet increases to normal.
• Within 8 hours: Carbon monoxide level in the blood drops to normal and oxygen levels in blood rise to normal. Smoker's breath disappears.
• Within 24 hours: Chance of heart attack decreases.
• Within 48 hours: Nerve endings start regenerating. Ability to taste and smell enhances.
• Within three days: You'll breathe easier.
• Within two weeks to three months: Circulation improves. Walking becomes easier. Lung function increases up to 30%.
• Within one to nine months: You'll cough less. Sinus congestion and shortness of breath decrease. The cilia that sweep debris from your lungs will grow back. You'll feel more energetic.
• Within one year: Excess risk of coronary heart disease is half that of a smoker.
• Within two years: Your heart attack risk drops to near normal.
• Within five years: Lung cancer death rate for average former smoker (of one pack a day) decreases by almost half. Stroke risk is reduced to that of a non-smoker five to 15 years after quitting. Risk of cancer of the mouth, throat, and esophagus is half that of a smoker's.
• Within 10 years: Lung cancer death rate is similar to that of a nonsmoker's. Pre-cancerous cells are replaced. Risk of cancer of the mouth, throat, esophagus, bladder, kidney, and pancreas decreases
• Within 15 years: Risk of coronary heart disease is that of a non-smoker's risk.

Source: American Cancer Society; Centers for Disease Control and Prevention