sentences:  This level was added during the 1948-to-1952 renovation, and contains the air conditioning and water softening equipment.The sub-basement and mezzanine also contain storage areas, the heating system, elevator machinery rooms, an incinerator, a medical clinic, a dentist's office, the electrical control system, a laundry room, and flatware and dishware storage.The Ground Floor of the White House originally contained service rooms.