Daily Code Talk #89: IMC 601 Part 2 (601.3 Exits)An exit enclosure is a protected exit component, usually an interior exit stairway or exit ramp, enclosed with fire-resistance-rated construction to protect the path of egress. IMC 601.3 is not about comfort HVAC. It is about how ventilation serving that protected space must be isolated, routed, and protected.

🧠 Plain-English Highlights• 601.3: Exit enclosure ventilation equipment and ductwork must follow one of the specific permitted arrangements in this section.• 601.3 item 1: Equipment and ductwork are permitted outside the building if they connect directly to the exit enclosure through ductwork enclosed as required by the IBC for shafts.• 601.3 item 2: Equipment and ductwork are permitted within the exit enclosure only where intake air is taken directly from outdoors and exhaust discharges directly outdoors, or where those air paths are routed through ductwork enclosed as required by the IBC for shafts.• 601.3 item 3: Equipment and ductwork located within the building but outside the exit enclosure must be separated from the rest of the building, including other mechanical equipment, with construction as required by the IBC for shafts.• 601.3: Openings into fire-resistance-rated construction must be limited to those needed for operation and maintenance and protected with self-closing fire-resistance-rated devices per the IBC.• 601.3: Exit enclosure ventilation systems must be independent of other building ventilation systems.🏗️ Why it mattersThis is a common coordination miss on permit sets. The plans may show a stair or exit enclosure fan, but not clearly show whether the system is truly independent, how the intake and discharge get outdoors, or how the rated enclosure is maintained. That turns into an easy redline.🗺️ Where to show it• M-001: IMC 601.3 compliance note and system description• M-101: equipment location, intake path, and discharge path• M-501: shaft, rated-wall, louver, and opening-protection details• M-601: Scheudle and Airflow Diagram• M-603 : Controls sequence• A/LS/E/FP sheets: rated enclosure, opening protection, power, and monitoring coordination✅ Do• Show which 601.3 compliance path the design is using• Make intake and discharge routing to outdoors explicit on plan• Coordinate shaft ratings and opening protection with architectural sheets⛔ Don’t• Don’t tie exit enclosure ventilation into general HVAC• Don’t leave intake or discharge routing vague• Don’t penetrate rated construction without showing the required protection🔧 Field tipReview exit enclosure ventilation as a full protected path, not just a fan callout. Trace intake, discharge, equipment location, shaft rating, and rated openings from end to end. If the path is not fully shown and coordinated, expect a redline.Comment “IMC601” if you want a paste-ready IMC 601 review checklist.