# Combustion Products: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/combustion-products/
- 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 | IRC 2009, IMC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IRC 2009 Fuel Gas (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 9 (counted across the codes hosted here) |
| Wording identical across codes | Yes (compare before citing one code's wording under another) |

## Direct answer

Combustion products is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “Constituents resulting from the combustion of a fuel with the oxygen of the air, including the inert gases, but excluding excess air.” The IMC 2009 carries the same definition word for word, so the term means the same thing in each. The term is used in 9 chapters of this corpus, most often in Chimneys and Vents (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](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?

**Combustion Products** — IRC 2009, Fuel Gas:

> Constituents resulting from the combustion of a fuel with the oxygen of the air, including the inert gases, but excluding excess air.

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

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

## What must be verified before using this guidance?

Two of the I-Codes in this corpus define **Combustion Products**, in identical words.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IRC 2009 | [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | Constituents resulting from the combustion of a fuel with the oxygen of the air, including the inert gases, but excluding excess air. |
| IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | Constituents resulting from the combustion of a fuel with the oxygen of the air, including the inert gases, but excluding excess air. |

## Where combustion products is used in the code

The term appears in 9 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Chimneys and Vents](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/chimneys-and-vents.md) | IMC 2009 | 10 |
| [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 8 |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 6 |
| [Chimneys and Vents](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/chimneys-and-vents.md) | IRC 2009 | 3 |
| [Refrigeration](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/refrigeration.md) | IMC 2009 | 2 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 2 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-protection-systems.md) | IBC 2009 | 1 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fire-protection-systems.md) | IFC 2009 | 1 |
| [Exhaust Systems](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/exhaust-systems.md) | IMC 2009 | 1 |

### The term in use

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

> Venting systems shall be designed and constructed so as to develop a positive flow adequate to convey all combustion products to the outside atmosphere.

— [IMC 2009 §801.4](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/chimneys-and-vents.md)

> chimneyinner wall or vent inner wall shall be continuous and shall be free of cracks, gaps, perforations, or other damage or deterioration that would allow the escape of combustion products, including gases, moisture and creosote.

— [IRC 2009 §G2425.15.2](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md)

> A venting system shall satisfy the draft requirements of the appliance in accordance with the manufacturer's installation instructions, and shall be constructed and installed to develop a positive flow to convey combustion products to the outside atmosphere.

— [IRC 2009 §M1801.2](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/chimneys-and-vents.md)


## The terms combustion products is built out of

The definition above leans on 2 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what combustion products covers:

- **[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.
- **[Excess Air](https://harth.build/resources/glossary/excess-air.md)** — IRC 2009: Air that passes through the combustion chamber and the appliance flue in excess of that which is theoretically required for complete combustion.

## Combustion Products: 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 IRC | Fuel Gas | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Chimneys and Vents (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 | Chimneys and Vents (IRC 2009) | |
| Confirm the dependent definition | Combustion | |
| Confirm the dependent definition | Excess Air | |
| 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)
- [Excess Air: Building Code Definition](https://harth.build/resources/glossary/excess-air.md)
- [Combustion: Building Code Definition](https://harth.build/resources/glossary/combustion.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 combustion products?

The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “Constituents resulting from the combustion of a fuel with the oxygen of the air, including the inert gases, but excluding excess air.” 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 combustion products?

In this corpus the term is used across 9 chapters, led by Chimneys and Vents 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 are combustion products?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Fuel Gas: “Constituents resulting from the combustion of a fuel with the oxygen of the air, including the inert gases, but excluding excess air.” 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.

---

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