IMC 701 begins with scoping. Solid-fuel appliances follow the manufacturer's installation instructions, oil-fired appliances follow NFPA 31, and gas-fired appliances follow the International Fuel Gas Code. The Chapter 7 combustion-air methods do not apply to fireplaces, fireplace stoves, or direct-vent appliances.
Plain-English Highlights
First select the correct governing path. Then prove that required combustion-air openings remain available when the appliance fires. Under 701.2, dampers in combustion-air openings must be interlocked 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 method. - Use manufacturer instructions and the governing referenced standard. - 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 say all of Chapter 7 is inapplicable to direct-vent appliances; the Chapter 7 combustion-air methods are the limited scope statement. - Do not use a manual damper in a required combustion-air opening. - Do not size an opening by nominal louver area when the product free area is lower.
Masterbuild QA Lens
Combustion air is an appliance-enclosure-controls system. Review the opening size, actual product free area, duct path, rated construction, exhaust-driven pressure, and firing permissive together.
Drawing / Submittal Check
For each appliance, record fuel, input, listing, governing standard, room condition, selected method, required free area, provided free area, opening path, damper type, and control interlock. Reconcile the schedule with product data.
Common Review Risk
Common comments include using the wrong code path, failing to account for louver free-area reduction, routing through rated construction without a coordinated protection path, and showing a damper without an automatic firing interlock.
When To Escalate
Escalate tight rooms, large exhaust systems, depressurized buildings, multiple appliances, unusual vertical or horizontal duct paths, rated shafts, or manufacturer instructions more restrictive than the prescriptive method.
Field Tip
Commission the system under the operating condition that creates the greatest negative pressure. Prove the opening or powered air source before enabling fuel and document the result.