Disable airplay auto connect

how do I disable or prevent macbook air auto connect to nearby airplay apple TV.

it happened when my macbook air auto connects to the nearby meeting room apply TV, and whatever it show on my screen it has been mirrored to the meeting room TV via apple TV without me knowing. This is terrible. until one of the colleague come to my desk and tell me to off my airplay. and the other department colleagues who use the meeting room can all see what on my screen and what I am doing..

I know for sure I did not touch the airplay, or connect to that apple TV.. but how come it can auto connect without my knowledge.

so this morning, I went to the office early and try to manually connect to that apple TV, it prompts me to enter a Passcode before connect. but this procedure wasn't there the other day when it auto connect????

it very scary now.. I could even lose my job if the sentitive information is been mirrored to the TV in another room without my notice...

is this a bug or is there anything I can do to prevent this from happening again??? I love my macbook but this is terrible incident happened