I am looking for a lock and handle mechanism for an exterior door that is always openable from the inside. E.g. locking with a key locks the exterior handle from opening the latch, but the interior handle always opens the door. Furthermore, operating the interior handle will not disengage the lock on the exterior handle. The closest analogy would be a commercial fire door, which remains locked but always allows egress.
Does a lock with the features I described above exist for residential or commercial markets, and do they go under a special name?