ASHRAE’srecently released Guideline 16-2003, Selecting Outdoor, Return, and Relief Dampers for Air-Side Economizer Systems, provides techniques for properly selecting dampers for the most common economizer relief system applications (return fans, relief fans and non-powered relief) and minimum outdoor air control strategies. The guide addresses the application and sizing of outdoor, return and relief dampers used to control outdoor air intake for economizer cooling, minimum ventilation outdoor airflow for indoor air quality and building pressure.