Not all plants are doing so and very few at the moment, but as of 2012 Comanche Peak Nuclear is doing hair follicle testing, and how that works is, they cut a hair right above the hair shaft a inch and a half and it goes back 90 days, it takes anywhere from 5-10 days for the drug or illegal substance to attach to hair shaft, beware recreational users, its a process of elimination, the economy is not getting any better, when they get this thing down to DNA test, folks you are not going to get away with jank.