Drug testing is a funny thing. Administered by companies, parole officers, parents, and in some cases, gossip websites, it’s essentially a system that allows the people who are forced to take them a way to abuse just about every drug, but the most benign one, pot. It stays in your system the longest and takes about a month to flush out, unlike cocaine, heroin, LSD, or prescription pills, which only take a few days. Keep that in mind next time a celeb fails a drug test for anything but weed. Here’s a handy chart.