The work fart

Hypothetical situation:

You share an office at work with one other person.  Your office mate is out of the room, but you don't know how long he'll be gone.  Maybe he went down the hall to ask someone a question and he'll be back any minute.  Maybe he's in a long meeting or even went to another building.  But you've got some gas building up and you'd like to let it out.  Your last fart was fairly stinky so you'd prefer not to let it out if your office mate is about to return.

What do you do?  How hard do you try to hold it in?  How long be for you give in and let it loose?