This standard encompasses the ventilation systems including equipment, piping, ductwork and control devices utilized for providing heat removal, heating, atmospheric cleanup, and general ventilation within pressurized water reactor containment structures. It includes systems which are used to ventilate containment structures even though the systems are physically located outside containment. This standard defines the design requirements of such equipment and systems and gives basic requirements and system arrangements with due consideration for construction, fabrication, surveillance, maintenance, and operation. This standard does not include liquid spray systems, closed water systems, or process support systems for subatmospheric or ice condenser containments. This standard is based upon the systems engineering criteria presented in American National Standard Nuclear Safety Criteria for the Design of Stationary Pressurized Water Reactor Plants, N18.2-1973/ANS-51.1.