Traps and Locks with Keys

What are the rules for traps when someone has the key?

For example, your players find a key after an encounter and take it with them. Eventually, they find a chest it fits, but (unknown to them) it is trapped and they don't bother checking and just unlock it, eager to get their hands on the anticipated goodies inside.

Does using the key bypass the trap? Or is the trap independant of the key and so still needs to be disabled (so, in the example above, it will still go off)?

Thanks in advance!

There is no general rule, it all depends on what sort of trap it is, how it is triggered, what purpose it has, etc.
Sometimes the key helps bypass the trap, often not.

If it is a magical trap set to explode on anyone opening the chest except the wizard that placed it the key will not help.

Thanks for the response, Henrix. I couldn't find any rules on it, but thought I just might be missing something. I'll post over in the general forum to see what other people do. Thanks!

This is being discussed in the general forum here

http://www.enworld.org/showthread.php?p=3098309