Saliva tests can go back as far as 96 hours. The only way to pinpoint how long it will take you to get clean is test yourself. If your going to be subjected to random testing your going to have to abstain for good. I don't think you will have enough time to prepare before a test. They do make detox products that may help but none are 100% reliable. I would stay clean for a while and see how the testing is conducted then you can figure out what you need to do to keep smoking.