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.