How long will the iPhone alarm ring for?

My roommate left her iPhone in her room and locked the door.
The alarm has started going off on FULL blast and it's now been ringing for over 30 minutes.
I can't get in to stop it and she won't be home till tomorrow.

How long will this iPhone alarm keep ringing for? I'm seriously about to snap! LOL!

You can just mute the phone, there's a Mute-Unmute switch on the left side of the phone, push the switch down and it'll mute the phone. How long will the iPhone alarm ring for