Building Code Glossary
Air, Makeup: Building Code Definition
How the IRC 2009, IMC 2009 define air, makeup, where the wording differs, and which chapters depend on the term.
On this page
Last updated September 7, 2026 · Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control.
Direct answer
Air, makeup is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “Air that is provided to replace air being exhausted.” The IMC 2009 carries the same definition word for word, so the term means the same thing in each. The term is used in 15 chapters of this corpus, most often in Exhaust Systems (IMC 2009), Fuel Gas (IRC 2009), Definitions (IMC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted. Record the jurisdiction, the adopted edition, the application date and any local amendment that rewrites the definition before you use it on a live project, because a term redefined by amendment changes every requirement that depends on it.
Content and cited inputs reviewed by Scott Barrington, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Air, Makeup — IRC 2009, Fuel Gas:
Air that is provided to replace air being exhausted.
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Air, Makeup, in identical words.
| Code | Where it is defined | Definition |
|---|---|---|
| IRC 2009 | Fuel Gas | Air that is provided to replace air being exhausted. |
| IMC 2009 | Definitions | Air that is provided to replace air being exhausted. |
Where air, makeup is used in the code
The term appears in 15 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Exhaust Systems | IMC 2009 | 58 |
| Fuel Gas | IRC 2009 | 13 |
| Definitions | IMC 2009 | 7 |
| Means of Egress | IBC 2009 | 6 |
| Flammable Finishes | IFC 2009 | 6 |
| Refrigeration | IMC 2009 | 6 |
| Commercial Energy Efficiency | IECC 2009 | 5 |
| Flammable and Combustible Liquids | IFC 2009 | 4 |
| Means of Egress | IFC 2009 | 4 |
| Duct Systems | IMC 2009 | 4 |
| Residential Energy Efficiency | IECC 2009 | 3 |
| Ventilation | IMC 2009 | 3 |
3 further chapters mention the term.
The term in use
How the code actually writes about air, makeup, quoted from the 2009 text hosted here:
If only a mechanical exhaust system is installed for a room or if a greater quantity of air is removed by a mechanical exhaust system than is supplied by a mechanical ventilating supply system for a room, adequate makeup air consisting of supply air, transfer air or outdoor air shall be provided to satisfy the deficiency.
Where exhaust fans, clothes dryers and kitchen ventilation systems interfere with the operation of appliances, makeup air shall be provided.
Provisions shall be made for makeup air to replace that being exhausted.
Air, Makeup: what to open, and in what order
Every row is a document this term depends on. The ICC code library and the ICC adoption maps cover the middle rows.
| Check | Where | Confirmed |
|---|---|---|
| Read the definition in the adopted IRC | Fuel Gas | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Exhaust Systems (IMC 2009) | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Re-check the requirement that uses it | Definitions (IMC 2009) | |
| Re-check the requirement that uses it | Means of Egress (IBC 2009) | |
| Local amendment to any of the above | Jurisdiction's amendment list |
A research aid, not a code determination. The authority having jurisdiction decides which edition and which amendments apply.
Where can you explore related guidance?
- Explore all glossary guidance
- Code Official: Building Code Definition
- Code: Building Code Definition
- Fuel Gas: Building Code Definition
- Vent: Building Code Definition
Sources and method
Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The ICC code library publishes the current model text and the ICC adoption maps show which edition a jurisdiction has adopted; those sources control.
Source links
Frequently asked questions
What is the code definition of air, makeup?
The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “Air that is provided to replace air being exhausted.” The 2009 model text is reproduced here; the definition that binds your project is the one in the edition your jurisdiction has adopted, as amended locally.
Which parts of the code depend on air, makeup?
In this corpus the term is used across 15 chapters, led by Exhaust Systems in the IMC 2009. Those are the sections whose scope moves if the definition is amended locally, so read them together with Chapter 2 rather than on their own.
What is considered make-up air?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Fuel Gas: “Air that is provided to replace air being exhausted.” It is defined in IRC 2009, IMC 2009. Because it is a defined term, whatever the adopted edition says it means is what every section using it means — so check Chapter 2 of that edition and any local amendment before relying on this wording.
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