# Ignition Source: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/ignition-source/
- 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 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 25 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Ignition source is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A flame, spark or hot surface capable of igniting flammable vapors or fumes. Such sources include appliance burners, burner ignitions and electrical switching devices.” The IMC 2009 defines the same term with different wording, so the controlling text depends on which code governs the question in front of you — the comparison below sets the versions side by side. The term is used in 25 chapters of this corpus, most often in General Regulations (IMC 2009), General Mechanical System Requirements (IRC 2009), Flammable and Combustible Liquids (IFC 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?

**Ignition Source** — IRC 2009, Definitions:

> A flame, spark or hot surface capable of igniting flammable vapors or fumes. Such sources include appliance burners, burner ignitions and electrical switching devices.

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

*How the IRC 2009, IMC 2009 define ignition source, 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 **Ignition Source**, and the wording is not identical — read the version that governs your question.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | A flame, spark or hot surface capable of igniting flammable vapors or fumes. Such sources include appliance burners, burner ignitions and electrical switching devices. |
| IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | A flame, spark or hot surface capable of igniting flammable vapors or fumes. Such sources include appliance burners, burner ignitors and electrical switching devices. |

## Where ignition source is used in the code

The term appears in 25 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [General Regulations](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/general-regulations.md) | IMC 2009 | 7 |
| [General Mechanical System Requirements](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/general-mechanical-system-requirements.md) | IRC 2009 | 6 |
| [Flammable and Combustible Liquids](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-and-combustible-liquids.md) | IFC 2009 | 5 |
| [General Requirements](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/general-requirements.md) | IFC 2009 | 5 |
| [Oxidizers, Oxidizing Gases and Oxidizing Cryogenic Fluids](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/oxidizers-oxidizing-gases-and-oxidizing-cryogenic-fluids.md) | IFC 2009 | 5 |
| [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 5 |
| [Flammable Finishes](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-finishes.md) | IFC 2009 | 4 |
| [Flammable Gases and Flammable Cryogenic Fluids](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-gases-and-flammable-cryogenic-fluids.md) | IFC 2009 | 4 |
| [Motor Fuel-dispensing Facilities and Repair Garages](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/motor-fuel-dispensing-facilities-and-repair-garages.md) | IFC 2009 | 4 |
| [Fruit and Crop Ripening](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fruit-and-crop-ripening.md) | IFC 2009 | 3 |
| [Liquefied Petroleum Gases](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/liquefied-petroleum-gases.md) | IFC 2009 | 3 |
| [Building Services and Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/building-services-and-systems.md) | IFC 2009 | 2 |

_13 further chapters mention the term._

### The term in use

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

> Equipment and appliances having an ignition source and located in hazardous locations and public garages, private garages, repair garages, automotive motor fuel-dispensing facilities and parking garages shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor surface on which the equipment or appliance rests.

— [IMC 2009 §304.3](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/general-regulations.md)

> Appliances having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor in garages.

— [IRC 2009 §M1307.3](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/general-mechanical-system-requirements.md)

> Equipment and appliances having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor in hazardous locations and public garages, private garages, repair garages, motor fuel-dispensing facilities and parking garages.

— [IRC 2009 §G2408.2](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md)


## The terms ignition source 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 ignition source covers:

- **[Flammable Vapors or Fumes](https://harth.build/resources/glossary/flammable-vapors-or-fumes.md)** — IBC 2009: The concentration of flammable constituents in air that exceed 25 percent of their lower flammable limit (LFL).
- **[Appliance](https://harth.build/resources/glossary/appliance.md)** — IRC 2009: Utilization equipment, normally built in standardized sizes or types, that is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying, etc.
- **[Burner](https://harth.build/resources/glossary/burner.md)** — IRC 2009: A device for the final conveyance of the gas, or a mixture of gas and air, to the combustion zone.

## Ignition Source: 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 | Definitions | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | General Regulations (IMC 2009) | |
| Re-check the requirement that uses it | General Mechanical System Requirements (IRC 2009) | |
| Re-check the requirement that uses it | Flammable and Combustible Liquids (IFC 2009) | |
| Re-check the requirement that uses it | General Requirements (IFC 2009) | |
| Confirm the dependent definition | Flammable Vapors or Fumes | |
| Confirm the dependent definition | Appliance | |
| Confirm the dependent definition | Burner | |
| 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)
- [Flammable Vapors or Fumes: Building Code Definition](https://harth.build/resources/glossary/flammable-vapors-or-fumes.md)
- [Appliance: Building Code Definition](https://harth.build/resources/glossary/appliance.md)
- [Burner: Building Code Definition](https://harth.build/resources/glossary/burner.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 ignition source?

The International Residential Code (IRC) 2009 defines it in Definitions as: “A flame, spark or hot surface capable of igniting flammable vapors or fumes. Such sources include appliance burners, burner ignitions and electrical switching devices.” 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 ignition source?

In this corpus the term is used across 25 chapters, led by General Regulations 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 the definition of an ignition source?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “A flame, spark or hot surface capable of igniting flammable vapors or fumes. Such sources include appliance burners, burner ignitions and electrical switching devices.” 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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