How long do you have to go without smoking or chewing tobacco to pass a tobacco swab screening test?

To be sure, at least: a week. Generally oral swabs will pick up any tobacco use within 3-5 days. I strongly suggest using that as a head start to complete cessation. Failing a cotinine screen (the metabolite of nicotine is what is actually measured) is nowhere near as bad as lung cancer, throat or mouth cancer, emphysema, heart attack or stroke, all of which are potentially waiting for you out there if you continue.