Drug testing question, nys?

i was wondering how most hospitals/nursing homes test nursing staff for drug usage, i have a cna friend who apparently was never even tested and they only test if something suspicious is happening. fyi i dont do drugs, but i have in the past toked on kush, like most have, i do it very rarely like once or twice every 6 months to a year. so im not worried about a urine test, but im worried it will be detected in my hair...last time i did it was about 2 months ago. does anyone know how hospitals/nursing homes test their staff ?(which method) and how far back hair is?? thanks!