# Air: Building Code Definition

> How the IMC 2009 define air, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/air/
- Last updated: 2026-09-07
- Data source: 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.

## Key facts

| Fact | Value |
| --- | --- |
| Defined in | IMC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IMC 2009 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 132 (counted across the codes hosted here) |
| Wording identical across codes | Single code (compare before citing one code's wording under another) |

## Direct answer

Air is a defined term in the International Mechanical Code (IMC) 2009, in Definitions. The code's own words are: “All air supplied to mechanical equipment and appliances for combustion, ventilation, cooling, etc. Standard air is air at standard temperature and pressure, namely, 70°P (21°C) and 29.92 inches of mercury (101.3 kPa).” No other I-Code in this corpus defines it, so the IMC 2009 definition is the one to work from. The term is used in 132 chapters of this corpus, most often in Means of Egress (IBC 2009), Means of Egress (IFC 2009), Fuel Gas (IRC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted.

*Content and cited inputs reviewed by [Scott Barrington](https://nz.linkedin.com/in/barrington), Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.*

## What does this term mean?

**Air** — IMC 2009, Definitions:

> All air supplied to mechanical equipment and appliances for combustion, ventilation, cooling, etc. Standard air is air at standard temperature and pressure, namely, 70°P (21°C) and 29.92 inches of mercury (101.3 kPa).

![Labeled code-term definition diagram: Air: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/air/diagram-1344.webp)

*How the IMC 2009 define air, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

**Air** is defined once in this corpus, in the [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) chapter of the International Mechanical Code (IMC) 2009:

> All air supplied to mechanical equipment and appliances for combustion, ventilation, cooling, etc. Standard air is air at standard temperature and pressure, namely, 70°P (21°C) and 29.92 inches of mercury (101.3 kPa).

## Where air is used in the code

The term appears in 132 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Means of Egress](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/means-of-egress.md) | IBC 2009 | 554 |
| [Means of Egress](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/means-of-egress.md) | IFC 2009 | 483 |
| [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 329 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fire-protection-systems.md) | IFC 2009 | 300 |
| [Exhaust Systems](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/exhaust-systems.md) | IMC 2009 | 298 |
| [Special Detailed Requirements Based on Use and Occupancy](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/special-detailed-requirements-based-on-use-and-occupancy.md) | IBC 2009 | 296 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-protection-systems.md) | IBC 2009 | 294 |
| [Commercial Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/commercial-energy-efficiency.md) | IECC 2009 | 278 |
| [Aviation Facilities](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/aviation-facilities.md) | IFC 2009 | 275 |
| [Duct Systems](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/duct-systems.md) | IMC 2009 | 239 |
| [Building Planning](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md) | IRC 2009 | 203 |
| [Ventilation](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/ventilation.md) | IMC 2009 | 202 |

_120 further chapters mention the term._

### The term in use

How the code actually writes about air, quoted from the 2009 text hosted here:

> The exterior area for assisted rescue must be open to the outside air and meet the requirements of Section 1007.6.1.

— [IBC 2009 §1007.7](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/means-of-egress.md)

> Corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts.

— [IFC 2009 §1018.5](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/means-of-egress.md)

> The requirements for combustion and dilution air for gas-fired appliances shall be governed by Section G2407.

— [IRC 2009 §G2404.2](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md)


## The terms air is built out of

The definition above leans on 3 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what air covers:

- **[Ventilation](https://harth.build/resources/glossary/ventilation.md)** — IBC 2009: The natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from, any space.
- **[Combustion](https://harth.build/resources/glossary/combustion.md)** — IRC 2009: In the context of this code, refers to the rapid oxidation of fuel accompanied by the production of heat or heat and light.
- **[Equipment](https://harth.build/resources/glossary/equipment.md)** — IRC 2009: All piping, ducts, vents, control devices and other components of systems other than appliances that are permanently installed and integrated to provide control of environmental conditions for buildings.

## Air: what to open, and in what order

Every row is a document this term depends on. The [ICC code library](https://codes.iccsafe.org/codes) and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) cover the middle rows.

| Check | Where | Confirmed |
| --- | --- | --- |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Means of Egress (IBC 2009) | |
| Re-check the requirement that uses it | Means of Egress (IFC 2009) | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Re-check the requirement that uses it | Fire Protection Systems (IFC 2009) | |
| Confirm the dependent definition | Ventilation | |
| Confirm the dependent definition | Combustion | |
| Confirm the dependent definition | Equipment | |
| 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](https://harth.build/resources/glossary.md)
- [Ventilation: Building Code Definition](https://harth.build/resources/glossary/ventilation.md)
- [Combustion: Building Code Definition](https://harth.build/resources/glossary/combustion.md)
- [Equipment: Building Code Definition](https://harth.build/resources/glossary/equipment.md)

## 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](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.

### Source links

- [codes.iccsafe.org](https://codes.iccsafe.org/codes)

- [iccsafe.org](https://www.iccsafe.org/advocacy/code-adoption-maps/)

## Frequently asked questions

### What is the code definition of air?

The International Mechanical Code (IMC) 2009 defines it in Definitions as: “All air supplied to mechanical equipment and appliances for combustion, ventilation, cooling, etc. Standard air is air at standard temperature and pressure, namely, 70°P (21°C) and 29.92 inches of mercury (101.3 kPa).” 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?

In this corpus the term is used across 132 chapters, led by Means of Egress in the IBC 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 are the requirements for ventilation in California building codes?

Ventilation is a separate defined term. The IBC 2009 defines it as: “The natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from, any space.” That is not the same as air, which the IMC 2009 defines as “All air supplied to mechanical equipment and appliances for combustion, ventilation, cooling, etc. Standard air is air at standard temperature and pressure, namely, 70°P (21°C) and 29.92 inches of mercury (101.3 kPa).” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

### What does air mean on a code reader?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IMC 2009 states, in Definitions: “All air supplied to mechanical equipment and appliances for combustion, ventilation, cooling, etc. Standard air is air at standard temperature and pressure, namely, 70°P (21°C) and 29.92 inches of mercury (101.3 kPa).” It is defined in 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.

---

- Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fair%2F
- View this page in a browser: https://harth.build/resources/glossary/air/
- All resources for agents: https://harth.build/llms.txt