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AIRFLOW around buildings affects worker safety, process and building equipment operation, weather and pollution protection at inlets, and the ability to control indoor temperature, humidity, air motion, and contaminants. Wind causes variable surface pressures on buildings that change intake and exhaust system flow rates, natural ventilation, infiltration and exfiltration, and interior pressures. The mean flow patterns and turbulence of wind passing over a building can recirculate exhaust gases to air intakes. This chapter provides basic information for evaluating windflow patterns, estimating wind pressures, and identifying problems caused by the effects of wind on intakes, exhausts, and equipment. In most cases, detailed solutions are addressed in other chapters. Related information can be found in Chapters 12, 14, 27, and 28 of this volume; in Chapters 29, 30, 44, 46, and 52 of the 2003 ASHRAE Handbook - HVAC Applications; and in Chapters 25,30, and 36 of the 2004 ASHRAE Handbook - HVAC Systems and Equipment.