no worries man I get high in the shower all the time and this always worked at my dads place

Steam up the room till its clearly visible
Cram a towel at the crack in the bottom of the door
Start up the extraction fan
Smoke away!

When your done smoking leave the shower and fan on for a good 10-15 mins

The dryer sheets rubber banded to a toilet paper tube works well if your that parinoid...