“Suspended ceilings are adapted to suspend from the rafters of a building or preexisting ceilings in order to lower a room ceiling. This type of ceiling is comprised of a plurality of parallel runners and cross members or bars, in order to provide a grid network defining rectangular spaces which panels are placed within, resting on the bars. The runners and bars are then concealed by the panels. The abutting edges are covered against free flow air and breathing between panels. When breathing does occur, the exposed surface becomes soiled and darkened due to the flow of dust-laden air between panels. The goals of this ceiling are economical manufacturing, easy installation and removal and replacement of panels, and reliability.”
- Byssing, George J. “3,055,469: Suspended Ceiling.” United States Patent Office, http://www.google.com/patents?id=PUlvAAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q&f=false (accessed April 11, 2010).