INTRODUCTION Wind can have a significant effect on the movement of smoke inside and outside a building and within underground transportation facilities. Wind pressures can dramatically alter exhaust and make-up airflow rates and airflow distributions. These problems can occur either for large building openings using natural venting strategies or for cases with powered exhaust coupled with naturally vented make-up air (e.g.@ open doors and windows). Underground transportation facilities are influenced by pressures on portals and pedestrian exit ways at the surface. All facilities have risks that the smoke exhausted from the building may be re-entrained into make-up air locations. Smoky air brought back into a building can adversely affect occupants trying to exit. The focus of this paper is on effects of wind on smoke control systems designed for large open spaces like atriums@ malls@ and airport terminal buildings. It does not directly address smoke control related to residential or commercial spaces such as in a high rise building nor does it address pressurized stairwell design issues. Useful references on the above topics are: Klote Milke (2002)@ the Society of Fire Protection Engineers (SFPE) Handbook on Fire Protection Engineering (2002)@ the National Fire Protection Association (NFPA) Fire Protection Handbook (2008)@ ASHRAE Handbook of Fundamentals?CChapter 16 (2005)@ ASHRAE Applications Handbook?CChapter 44 (2007)@ and NFPA Standard 92B (2008). Inside a building@ wind pressure effects on smoke control can be predicted with zone@ network@ and computational fluid dynamics models within the building. Outside a building@ measurements on a physical scale model in a wind tunnel can provide wind pressure coefficients inputs to these models that account for the effects of nearby buildings. Wind tunnel testing can highlight the dispersion of smoke outside the building and quantify the concentration of smoke that may re-enter the building and determine the conditions under which it may occur. This paper explains some complexities about wind flows around buildings and how these wind flows can affect exhaust and intake openings. It illustrates external wind flows with sketches and examples from wind tunnel test results. The paper also proposes a framework to establish an external dilution target to aid designers in determining the separation of exhaust and intakes for smoke control systems. Furthermore@ the likelihood of wind disturbing naturally ventilated makeup air is also examined.