Wire being installed in the ceiling of an office in a multistory building must almost always be fireproof cable, often called plenum or Teflon. Plenum refers to the type of ceiling where the air in your office circulates through a main air handling system and goes into other offices. A fire in your ceiling that burns regular PVC cable will give off poisonous gas that can kill people trapped in other areas of the building. The cable in your ceiling must be a "plenum rated cable" or standard cable that is encased in a metal conduit so any fumes from a fire in the ceiling will not get into the air handling system.

Asking your installer to save a few bucks and illegally use regular cable in the ceiling opens you and your installer up to huge legal liability. If someone died in a building fire and they found you liable because you wrongly installed PVC cable in the ceiling, they could take your company, your house, your Harley and still send you to jail. For ceiling installation, any cable in a metal conduit is OK, and any cable specifically labeled for plenum use is OK, it does not have to be cable with the brand name Teflon.