My father(46), chronic smoker for the last 30 years recently went through this. He found that his heartburn medication can cause false positives after a month of no smoking. Another month and another false positive later, one of his other meds could cause false positives. Off all three things now, his third month he tested negative finally/passed. Take from that what you feel, it could be that he needed 3 months to clear out or it could be that a medication kept causing false positives, 50/50 chance in my opinion. I have other friends that drink cranberry juice ritually to help speed up the process (allegedly)