Ipad Air2

Am I mistaken but I was under the impression that after downloading iOS9 on an iPad Air2 that you could use the " Hey Siri " function hands free like you can on the new iPhone. My iPhone with the Hey Siri feature works great but I cant get it to work on my iPad Air2. As I said, was I mistaken in thinking that " Hey Siri " worked hands free after downloading iOS9? If Im wrong this is going to be a big disappointment 😟 IF it does work with iOS9 can someone tell me how to get it activated? Thank you in advance.