Communication centers include telephone terminal buildings, radio stations, television studios, and transmitter and receiver stations. Most telephone terminal rooms are air conditioned because constant temperature and relative humidity help prevent breakdowns and increase equipment life. In addition, air conditioning permits the use of a lower number of air changes, which, for a given filter efficiency, decreases the chances of damage to relay contacts and other delicate equipment. Radio and television studios require critical analysis for the elimination of heat buildup and the control of noise. Television studios have the added problem of air movement, lighting, and occupancy load variations. This section deals with television studios because they present most of the problems also found in radio studios. Load Characteristics Human occupancy is limited, so the air-conditioning load for telephone terminal rooms is primarily equipment heat load. Television studios have very high lighting capacities, and the lighting load may fluctuate considerably in intensity over short periods. The operating hours may vary every day. In addition, there may be from one to several dozen people onstage for short times. The airconditioning system must be extremely flexible and capable of handling wide load variations quickly, accurately, and efficiently, similar to the conditions of a theater stage. The studio may also have an assembly area with a large number of spectator seats. Generally, studios are located so that they are completely shielded from external noise and thermal environments.

Design Concepts The critical areas of a television studio are the performance studio and control rooms. The audience area may be treated much like a place of assembly. Each area should have its own air distribution system or at least its own zone control separate from the studio system. The heat generated in the studio area should not be allowed to permeate the audience atmosphere. The air distribution system selected must have the capabilities of a dual-duct, single-duct system with cooling and heating booster coils, a variable air volume systems, or a multizone system to satisfy design criteria.

The air distribution system should be designed so that simultaneous heating and cooling cannot occur unless heating is achieved solely by heat recovery. Studio loads seldom exceed 350 kW of refrigeration. Even if the studio is part of a large communications center or building, the studio should have its own refrigeration system in case of emergencies. The refrigeration equipment in this size range may be reciprocating units, which require a remote location so that machine noise is isolated from the studio. Special Considerations On-Camera Studios. This is the stage of the television studio and requires the same general considerations as a concert hall stage. Air movement must be uniform, and, because scenery, cameras, and equipment may be moved during the performance, ductwork must be planned carefully to avoid interference with proper studio operation. Control Rooms. Each studio may have one or more control rooms serving different functions. The video control room, which is occupied by the program and technical directors, contains monitors and picture-effect controls. The room may require up to 30 air changes per hour to maintain proper conditions. The large number of necessary air changes and the low sound level that must be maintained require special analysis of the air distribution system. If a separate control room is furnished for the announcer, the heat load and air distribution problems will not be as critical as those for control rooms for the program, technical, and audio directors.

. To prevent transmission of vibration, piping should be supported from rigid structural elements to maximize absorption. Mechanical Equipment Rooms. These rooms should be located as remotely from the studio as possible. All equipment should be selected for very quiet operation and should be mounted on suitable vibration-eliminating supports. Structural separation of these rooms from the studio is generally required. Offices and Dressing Rooms. The functions of these rooms are quite different from each other and from the studio areas. It is recommended that such rooms be treated as separate zones, with their own controls. Air Return. Whenever practicable, the largest portion of studio air should be returned over the banks of lights. This is similar to theater stage practice. Sufficient air should also be removed from studio high points to prevent heat buildup.