# Flammable Gas: Building Code Definition

> How the IBC 2009, IFC 2009 define flammable gas, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/flammable-gas/
- 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 | IBC 2009, IFC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IBC 2009 Use and Occupancy Classification (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 17 (counted across the codes hosted here) |
| Wording identical across codes | No (compare before citing one code's wording under another) |

## Direct answer

Flammable gas is a defined term in the International Building Code (IBC) 2009, in Use and Occupancy Classification. The code's own words are: “A material that is a gas at 68°F (20°C) or less at 14.7 pounds per square inch atmosphere (psia) (101 kPa) of pressure [a material that has a boiling point of 68of (20°C) or less at 14.7 psia (101 kPa)] which:” The IFC 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 17 chapters of this corpus, most often in Flammable Gases and Flammable Cryogenic Fluids (IFC 2009), Special Detailed Requirements Based on Use and Occupancy (IBC 2009), Motor Fuel-dispensing Facilities and Repair Garages (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?

**Flammable Gas** — IBC 2009, Use and Occupancy Classification:

> A material that is a gas at 68°F (20°C) or less at 14.7 pounds per square inch atmosphere (psia) (101 kPa) of pressure [a material that has a boiling point of 68of (20°C) or less at 14.7 psia (101 kPa)] which:

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

*How the IBC 2009, IFC 2009 define flammable gas, 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 **Flammable Gas**, and the wording is not identical — read the version that governs your question.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IBC 2009 | [Use and Occupancy Classification](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/use-and-occupancy-classification.md) | A material that is a gas at 68°F (20°C) or less at 14.7 pounds per square inch atmosphere (psia) (101 kPa) of pressure [a material that has a boiling point of 68of (20°C) or less at 14.7 psia (101 kPa)] which: |
| IFC 2009 | [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) | A material which is a gas at 68°F (20°C) or less at 14.7 pounds per square inch atmosphere (psia) (101 kPa) of pressure [a material that has a boiling point of 68°F (20°C) or less at 14.7 psia (101 kPa)] which: |

## Where flammable gas is used in the code

The term appears in 17 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [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 | 58 |
| [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 | 27 |
| [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 | 13 |
| [Semiconductor Fabrication Facilities](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/semiconductor-fabrication-facilities.md) | IFC 2009 | 11 |
| [Compressed Gases](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/compressed-gases.md) | IFC 2009 | 7 |
| [Definitions](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/definitions.md) | IFC 2009 | 4 |
| [Use and Occupancy Classification](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/use-and-occupancy-classification.md) | IBC 2009 | 3 |
| [Fire Safety During Construction and Demolition](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fire-safety-during-construction-and-demolition.md) | IFC 2009 | 3 |
| [General Requirements](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/general-requirements.md) | IFC 2009 | 3 |
| [Exhaust Systems](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/exhaust-systems.md) | IMC 2009 | 3 |
| [Welding and Other Hot Work](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/welding-and-other-hot-work.md) | IFC 2009 | 2 |
| [General Regulations](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/general-regulations.md) | IMC 2009 | 2 |

_5 further chapters mention the term._

### The term in use

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

> Static-producing equipment located in flammable gas storage areas shall be grounded.

— [IFC 2009 §3503.1.4.1](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-gases-and-flammable-cryogenic-fluids.md)

> Repair garages used for repair of vehicles fueled by nonodorized gases, such as hydrogen and nonodorized LNG, shall be provided with a flammable gas detection system.

— [IFC 2009 §2211.7.2](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/motor-fuel-dispensing-facilities-and-repair-garages.md)

> The interior of a vault containing a flammable gas shall be designated a Class I, Division 1 location, as defined in NFPA 70.

— [IFC 2009 §3003.16.14](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/compressed-gases.md)


## Flammable Gas compared with Liquid

These two are the closest pair in the 2009 I-Codes: about 48 per cent of their defining words are the same. The code states both and compares neither, so the difference is worth naming.

| | Wording unique to it |
| --- | --- |
| **Flammable Gas** (IBC 2009) | gas, atmosphere, pressure, 68of |
| [Liquid](https://harth.build/resources/glossary/liquid.md) (IBC 2009) | melting, equal, greater, absolute, when, otherwise, identified, term, liquid, includes, both, flammable |

Everything else in the two definitions is shared. If a project turns on which of the two applies, those words are the whole of the test — and a local amendment that edits one of them without editing the other moves the boundary between flammable gas and liquid.

## The terms flammable gas is built out of

The definition above leans on 1 other defined term. Each carries its own code definition, and a local amendment to any of them changes what flammable gas covers:

- **[Boiling Point](https://harth.build/resources/glossary/boiling-point.md)** — IBC 2009: The temperature at which the vapor pressure of a liquid equals the atmospheric pressure of 14.7 pounds per square inch (psi) (101 kPa) gage or 760 mm of mercury.

## Flammable Gas: 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 IBC | Use and Occupancy Classification | |
| Read the definition in the adopted IFC | Flammable Gases and Flammable Cryogenic Fluids | |
| Re-check the requirement that uses it | Flammable Gases and Flammable Cryogenic Fluids (IFC 2009) | |
| Re-check the requirement that uses it | Special Detailed Requirements Based on Use and Occupancy (IBC 2009) | |
| Re-check the requirement that uses it | Motor Fuel-dispensing Facilities and Repair Garages (IFC 2009) | |
| Re-check the requirement that uses it | Semiconductor Fabrication Facilities (IFC 2009) | |
| Confirm the dependent definition | Boiling Point | |
| 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)
- [Boiling Point: Building Code Definition](https://harth.build/resources/glossary/boiling-point.md)
- [Corrosive: Building Code Definition](https://harth.build/resources/glossary/corrosive.md)
- [Hazardous Materials: Building Code Definition](https://harth.build/resources/glossary/hazardous-materials.md)
- [Combustible Liquid: Building Code Definition](https://harth.build/resources/glossary/combustible-liquid.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 flammable gas?

The International Building Code (IBC) 2009 defines it in Use and Occupancy Classification as: “A material that is a gas at 68°F (20°C) or less at 14.7 pounds per square inch atmosphere (psia) (101 kPa) of pressure [a material that has a boiling point of 68of (20°C) or less at 14.7 psia (101 kPa)] which:” 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 flammable gas?

In this corpus the term is used across 17 chapters, led by Flammable Gases and Flammable Cryogenic Fluids in the IFC 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 a flammable gas?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IBC 2009 states, in Use and Occupancy Classification: “A material that is a gas at 68°F (20°C) or less at 14.7 pounds per square inch atmosphere (psia) (101 kPa) of pressure [a material that has a boiling point of 68of (20°C) or less at 14.7 psia (101 kPa)] which:” It is defined in IBC 2009, IFC 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%2Fflammable-gas%2F
- View this page in a browser: https://harth.build/resources/glossary/flammable-gas/
- All resources for agents: https://harth.build/llms.txt