IMC Chapter 6 is where airflow design becomes a buildable, inspectable duct system. A compliant design is more than a duct route: the materials, pressure class, insulation, rated penetrations, access, controls, and final balancing must all agree.
Chapter Map
601 General establishes the system framework. 602 governs plenums. 603 covers duct construction and installation. 604 addresses insulation. 605 covers air filters. 606 covers smoke detection and controls. 607 protects rated and smoke-resistive assemblies. 608 requires field balancing.
Permit Proof Chain
System intent -> code and pressure class -> material and construction standard -> insulation and environmental protection -> filter and detection requirements -> rated-assembly protection -> access and controls -> measured final airflow.
Where To Show It
M-001: code notes, duct standards, insulation, testing, and balancing. M-101: routing, sizes, airflow, rated crossings, access, and coordination. M-501: construction, penetration, damper, liner, and weather details. M-603: smoke detection, shutdown, and control sequences.
Do
Coordinate duct routing with the architectural life-safety plan.
Match construction and reinforcement to pressure and service.
Show insulation, vapor control, exterior weather protection, and access.
Carry Chapter 4 airflow requirements through to final TAB.
Do Not
Treat plenums, shafts, rated walls, and ceiling membranes as interchangeable.
Use a generic damper symbol without assembly type, listing, controls, and access.
Leave external duct protection or field balancing to an undefined contractor decision.
Masterbuild QA Lens
Run Chapter 6 as a coordinated review across plans, details, schedules, controls, specifications, and the architectural life-safety sheets. Most expensive failures occur at the handoffs between those documents.
Drawing / Submittal Check
Select several representative systems and trace them from equipment to terminal or discharge. Verify material, pressure class, insulation, rated crossings, access, controls, and scheduled airflow at each step.
Common Review Risk
The chapter is often reviewed as isolated details. That misses cross-document conflicts such as flex through a rated line, inaccessible dampers, missing weather protection, or TAB requirements that cannot be measured.
When To Escalate
Escalate unusual materials, constrained shafts, engineered smoke control, penetrations without a listed path, exposed exterior ductwork, or systems that cannot be balanced to the required pressure relationship.
Field Tip
Before ceilings close, walk the highest-risk duct paths with mechanical, architectural, firestopping, controls, and TAB responsibilities visible. One coordinated walk can prevent several separate return visits.
Project Basis Gate
For each representative duct system, establish the pressure/service basis, construction and material standard, insulation/vapor/weather protection, plenum condition, rated-assembly crossings, damper and smoke-detection requirements, access path, and required final balancing outcome. The duct route alone is not the system basis.
Project-Team Handoff
Architecture and life-safety identify rated walls, shafts, ceilings, plenums, and access-panel locations. MEP defines duct class, sizing, insulation, external exposure, terminals, and test/balance intent. Firestopping/damper trades provide listed assembly evidence. Controls provides sequences and smoke response. TAB confirms the final measured airflow and pressure relationship. Tie those documents to the same system designation.
Field Release Gate
Before ceilings close, inspect the highest-risk runs in plan and field: material and reinforcement, insulation continuity, supports, access doors, damper orientation/access, rated penetrations, smoke detection, exterior weather protection, and test ports. Do not wait for TAB to discover that the design cannot be measured or maintained.
Final Decision Rule
A Chapter 6 system is complete only when it can be built, inspected, accessed, controlled, and balanced as the documents describe - not merely routed through available space.