An operating theater (also known as an operating room, operating suite, theater operation suite or OR) is a facility within a hospital where surgical operations are carried out in a sterile environment. Historically, the term ''operating theater'' referred to a non-sterile, tiered theater or amphitheater in which students and other spectators could watch surgeons perform surgery..http://www.airtech.com.sg/product/productdetails/surgical-room-ceiling