An engineered natural ventilation system for a large atrium has been approved by the Authority Having Jurisdiction. According to Section 402.2, must this system also include a mechanical ventilation system designed in accordance with Sections 403.0 or 404.0?

• Yes, all natural ventilation systems must have a complementary mechanical system.
• No, the AHJ-approved engineered system is exempt from the requirement to have a mechanical system.
• No, but only if the openings are permanently open.
• Yes, but the mechanical system only needs to run when the natural system is insufficient.