IMC 606.3 is where smoke detector placement becomes more than a symbol on the plan. The detector has to be installed per NFPA 72, monitor the full airflow being conveyed, and remain accessible for inspection and maintenance.
🧠 Plain-English Highlights
• 606.3 Installation
- Required smoke detectors must be installed in accordance with NFPA 72.
- Detectors must monitor the entire airflow conveyed by the system.
- This includes return air and exhaust or relief air where those airstreams are part of the system being monitored.
- Access must be provided for inspection and maintenance.
🏗️ Why it matters
A detector symbol is not enough. If the detector is placed where it only samples part of the airflow, is blocked by equipment, or cannot be accessed after construction, the design may technically show smoke detection but still fail the intent of IMC 606.
🗺️ Where to show it
• M-001: IMC 606.3 / NFPA 72 installation note
• M-101: detector locations relative to return, exhaust, and relief air paths
• M-501: duct smoke detector installation and access details
• M-601: AHU / RTU / fan schedule with smoke detector requirement
• M-603 / FA / E: shutdown sequence, fire alarm interface, and device coordination
✅ Do
• Show detector locations where the full airflow is monitored
• Coordinate installation with NFPA 72 requirements
• Provide access for inspection, testing, and maintenance
• Confirm return, exhaust, and relief air paths are considered
⛔ Don’t
• Don’t place detectors where they only sample partial airflow
• Don’t bury detectors above inaccessible ceilings or behind equipment
• Don’t show smoke detection without coordinating FA interface and shutdown
🔧 Field tip
Trace the actual airflow, not just the duct line. If return, exhaust, or relief air bypasses the detector location, the detector may not be monitoring the full system airflow. That is the kind of issue that turns into a redline or failed inspection.
Comment “IMC606” if you want a paste-ready smoke detection systems control checklist + M-001 note set.