IMC Chapter 7 governs combustion air - the enclosure, opening, and control requirements that keep a fuel-fired appliance's air supply available for as long as it's firing. Chapter 7's combustion-air methods live in a single section, 701, which this series covered in full.
Chapter Map
701 (Combustion Air): Scope by fuel type - solid-fuel appliances follow the manufacturer's installation instructions, oil-fired appliances follow NFPA 31, and gas-fired appliances follow the IFGC instead of Chapter 7. Fireplaces, fireplace stoves, and direct-vent appliances are outside the Chapter 7 combustion-air methods. 701.2 requires the automatic interlock: dampers in a required combustion-air opening must open with the firing cycle - manual dampers are prohibited.
Permit Proof Chain
Fuel and appliance type -> listed installation instructions and governing standard -> room/enclosure classification -> combustion-air method and sizing -> opening location and rated-assembly coordination -> damper/fan interlock -> commissioning test.
Where To Show It
M-001: governing code path and combustion-air basis. M-101: appliance room, openings, ducts, louvers, and clear free area. M-501: opening, damper, duct, and rated-assembly details. M-603: interlock, proof, alarm, and failure sequence.
**Do**
Identify fuel and appliance type before selecting a combustion-air method.
Use manufacturer instructions and the governing referenced standard - NFPA 31 for oil, the IFGC for gas.
Coordinate net free area, louvers, screens, dampers, ducts, and pressure effects.
Show the automatic interlock and verify the opening before firing.
**Do Not**
Do not treat all of Chapter 7 as inapplicable just because a project has direct-vent appliances; the limited-scope statement applies to the combustion-air methods, not the whole chapter.
Do not use a manually operated damper in a required combustion-air opening.
Do not size an opening using nominal louver area when the manufacturer's product free area is lower.
Masterbuild QA Lens
Chapter 7 is short, but combustion air is an appliance-enclosure-controls system, not a single calculation. A design that gets the opening size right can still fail if the duct path, rated-construction coordination, or firing interlock isn't verified alongside it.
Drawing / Submittal Check
For every fuel-fired appliance on the schedule, record fuel type, input, listing, governing standard, room condition, selected combustion-air method, required free area, provided free area, opening path, damper type, and control interlock. Reconcile the schedule against product data before submittal.
Common Review Risk
The most common Chapter 7 comments: using the wrong governing code path for the fuel type, failing to account for louver free-area reduction, routing combustion-air ducts through rated construction without a coordinated protection path, and showing a damper with no automatic firing interlock.
When To Escalate
Escalate tight rooms, large exhaust systems, depressurized buildings, multiple appliances sharing a combustion-air source, unusual vertical or horizontal duct paths, rated shafts, or manufacturer instructions more restrictive than the prescriptive method.
Field Tip
Commission the combustion-air system under the operating condition that creates the greatest negative pressure in the space - not just at rest. Prove the opening or powered air source before enabling fuel, and document the result.