Before the phrase 'displacement ventilation' was even coined, the available height of KTVU television studios was used taking advantage of the natural stratification in an innovative concept. The 72 F low return air from the occupied lower level of the studio was resupplied to the upper level of the studio above the lights. The air in the studio is used twice - the first time supplied, from overhead out of sight, to cool the occupied level and the second time to skim the heat of the lights maintaining 90 F to protect the overhead lights and equipment.