The first edition, published in 2007, was designed as a companion to Industrial Ventilation: A Manual of Recommended Practice for Design (the Design Manual) to complement its information. The Design Manual is a guide to assist practitioners in designing an industrial ventilation system to control airborne contaminants that can become health hazards in the workplace. The second edition of the O&M Manual provides new, useful and practical knowledge as well as application-specific tools to install, operate and maintain your ventilation system. Checklists and forms are included that will make maintaining your ventilation system easy and orderly. A new chapter on Energy has been added and includes CFD figures and a subsection regarding the new AMCA FEI energy rating system. A revamped section for system and hood testing and Ce is also included.