GENERAL DESIGN CRITERIA Space-conditioning systems in power plant buildings are designed to maintain an environment for reliable operation of power generation systems and equipment and for the convenience and safety of plant personnel. A balance is achieved between the cost of the process systems designed to operate in an environment and the cost of providing that environment. Environmental criteria for personnel safety and comfort are governed by several sources. The U.S. Occupational Safety and Health Administration (OSHA) defines noise@ thermal environment@ and air contaminant exposure limits. Chapters 12 and 29 of this volume and Industrial Ventilation by the American Conference of Governmental Industrial Hygienists (ACGIH 2004) also provide guidance for safety in work spaces@ primarily in the areas of industrial ventilation and worker-related heat stress. The degree of worker comfort is somewhat subjective and more difficult to quantify. The plant owner or operator ordinarily establishes the balance between cost and worker comfort. Exhaust vents are subject to regulation of the plant's air quality permit and local air pollution control board's requirements. For this reason@ all exhaust vent locations should be properly identified and classified@ and coordinated with the plant's environmental compliance department. Treatment of exhaust streams is discussed in Chapter 25 of the 2004 ASHRAE Handbook??HVAC Systems and Equipment. Criteria should be clearly defined at the start of design@ because they document an understanding between the process designer and the HVAC system engineer that is fundamental to achieving the environment required for the various process areas. Typical criteria for a coal-fired power plant are outlined in Table 1. They should be reviewed for compliance with local codes@ the plant operator's experience and preferences@ and the overall financial objectives of the facility. Additional discussion of criteria may be found in the sections on specific areas.