Yeah get a lock on your door pronto.

I was smokin in my room once, making sure to blow all the smoke out my window. I'd done this a couple times before and my parents didnt notice so I didnt think there was anything different this time. For some reason when my parents came home the entire house smelled like weed (i guess another window was open and the smoke trailed in there or something)
My mom came in telling me "THIS ROOM STINKS OF POT!" I denied it of course and ended up blaming it on my step sister, she bought it. Its gotta be the worst feeling thinking your about to get rolled.
Now i just light candles constantly and use one of those bottles stuffed with dryer sheets to kill the smell (what a marvelous invention).