There is no actual proof that Naicin works, but if you do some research on the net, there are people who are making themselves very sick & even dying from Niacin overdoses, so be careful.
If you quite for a month, there is a good chance, depending on your usage, that you will be clean on your own, or you could take a natural detox product the day of the test, just to cover any residue that there might be. I've used Rescue Cleanse in the past and it worked great!
I took niacin 3 days prior to a drug screening and drunk plenty of water.. I took around 2500 mg a day and 1000mg before my drug screening.. It worked for me.. Just stop smoking for a week or two and you should be just fine..