Plenum rated Cat.5E cable has the same data transmission specifications as regular Cat.5E, but has a jacket that meets specific ANSI requirements for flame retardance and low smoke production. If the building is involved in a fire, the Cat5e Plenum cable will not burn as easy as a standard PVC jacket, and will produce less smoke than a typical Cat5e cable if it does catch fire. It is generally used in public building or HIPPA compliant office environments.