IMC 608 turns airflow from a design value into a field-verification obligation. Air distribution, ventilation, and exhaust systems must include a practical means of adjustment and must be balanced by an approved method.
Plain-English Highlights
The permit set establishes required airflow. The installed system still has to prove that it delivers it. Dampers, balancing devices, accessible test points, controls, and a final testing and balancing report are the evidence chain.
Permit Proof Chain
Required Chapter 4 airflow -> scheduled design airflow -> installed adjustment means -> approved balancing method -> final measured airflow -> documented correction of deficiencies.
Where To Show It
M-001: testing and balancing specification and acceptance criteria. M-101: air quantities at terminals and adjustment devices. M-601: equipment and fan schedules. Specifications: approved TAB agency, procedures, tolerances, reporting, and corrective work.
**Do** - Schedule supply, return, outdoor, relief, and exhaust air quantities. - Provide accessible balancing dampers or other adjustment means. - Coordinate controls and fan operating modes used during testing. - Require a final report that identifies design, preliminary, and final readings.
**Do Not** - Treat the scheduled CFM as proof of installed performance. - Hide balancing devices above inaccessible construction. - Accept a report that omits operating mode, fan speed, or unresolved deficiencies.
Masterbuild QA Lens
Review balancing as a closeout deliverable that starts during design. If the drawings do not show measurable air quantities, adjustment points, access, and control modes, the TAB contractor cannot create reliable proof later.
Drawing / Submittal Check
Trace every required Chapter 4 airflow to a terminal, intake, exhaust point, equipment schedule, and TAB line item. Confirm the sum of terminal values reconciles with system airflow and that adjustment devices remain accessible.
Common Review Risk
The recurring failure is a generic note to balance the system without scheduled terminal values, tolerances, approved procedures, or a defined response when measured airflow is low.
When To Escalate
Escalate when measured outdoor or exhaust airflow cannot meet the code basis, when pressure relationships are critical, when controls prevent stable test conditions, or when the system lacks enough adjustment authority.
Field Tip
Do a pre-TAB readiness walk before ceilings close: confirm device access, damper position, filter condition, fan rotation, control mode, terminal installation, and that every test point can be reached.