What Is the Purpose of This Weird Door?

Core77 directs our attention to this unusual door manufactured by the New Jersey-based firm Construction Specialties. The door has a door inside. Why? The answer is below the fold.

This is a barrier-resistant door. It's made with mental health facilities in mind. If a patient barricades him or herself inside, staff can still force entry with an inner door that opens into the exterior space. A patient might be able to barricade the outer door, but not the inner one.