Within 20 minutes of quitting smoking, your pulse returns to normal and nicotine and carbon monoxide levels in your blood begin to drop significantly. Over the next few days and weeks, traces of nicotine are removed from your body, breathing becomes easier as lungs start to clear out smoking debris, and taste and smell improve as circulation increases. After a year, the risks of heart attack and lung cancer reduce by half compared to a continuing smoker, and after 15 years, the heart attack risk equals that of someone who never smoked.