Building Code Glossary
Flammable Vapors or Fumes: Building Code Definition
How the IBC 2009, IFC 2009 define flammable vapors or fumes, 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
Flammable vapors or fumes is a defined term in the International Building Code (IBC) 2009, in Special Detailed Requirements Based on Use and Occupancy. The code's own words are: “The concentration of flammable constituents in air that exceed 25 percent of their lower flammable limit (LFL).” 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 7 chapters of this corpus, most often in Definitions (IBC 2009), Special Detailed Requirements Based on Use and Occupancy (IBC 2009), Definitions (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, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Flammable Vapors or Fumes — IBC 2009, Special Detailed Requirements Based on Use and Occupancy:
The concentration of flammable constituents in air that exceed 25 percent of their lower flammable limit (LFL).
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Flammable Vapors or Fumes, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IBC 2009 | Special Detailed Requirements Based on Use and Occupancy | The concentration of flammable constituents in air that exceed 25 percent of their lower flammable limit (LFL). |
| IFC 2009 | Hazardous Materials-general Provisions | The concentration of flammable constituents in air that exceeds 25 percent of their lower flammable limit (LFL). |
Where flammable vapors or fumes is used in the code
The term appears in 7 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Definitions | IBC 2009 | 1 |
| Special Detailed Requirements Based on Use and Occupancy | IBC 2009 | 1 |
| Definitions | IFC 2009 | 1 |
| Hazardous Materials-general Provisions | IFC 2009 | 1 |
| Definitions | IMC 2009 | 1 |
| Definitions | IRC 2009 | 1 |
| Fuel Gas | IRC 2009 | 1 |
Flammable Vapors or Fumes: 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 IBC | Special Detailed Requirements Based on Use and Occupancy | |
| Read the definition in the adopted IFC | Hazardous Materials-general Provisions | |
| Re-check the requirement that uses it | Definitions (IBC 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 | Definitions (IFC 2009) | |
| Re-check the requirement that uses it | Hazardous Materials-general Provisions (IFC 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
- Liquid: Building Code Definition
- Solid: Building Code Definition
- Platform: Building Code Definition
- Cell: 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 flammable vapors or fumes?
The International Building Code (IBC) 2009 defines it in Special Detailed Requirements Based on Use and Occupancy as: “The concentration of flammable constituents in air that exceed 25 percent of their lower flammable limit (LFL).” 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 vapors or fumes?
In this corpus the term is used across 7 chapters, led by Definitions 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.
Related pages
- Flammable Material: Building Code Definition
Flammable Material — IBC 2009 definition: A material capable of being readily ignited from common sources of heat or at a temperature …
- Flammable Solid: Building Code Definition
Flammable Solid — IBC 2009 definition: A solid, other than a blasting agent or explosive, that is capable of causing fire through …
- Flammable Vapor Area: Building Code Definition
Flammable Vapor Area — IFC 2009 definition: An area in which the concentration of flammable constituents (vapor, gas, fume, mist or dust) in …
- Flash Point: Building Code Definition
Flash Point — IBC 2009 definition: The minimum temperature in degrees Fahrenheit at which a liquid will give off sufficient vapors to …
- Fleet Vehicle Motor Fuel-dispensing Facility: Building Code Definition
Fleet Vehicle Motor Fuel-dispensing Facility — IFC 2009 definition: That portion of a commercial, industrial, governmental or manufacturing property where liquids used as f…
- Flight: Building Code Definition
Flight — IBC 2009 definition: A continuous run of rectangular treads, winders or combination thereof from one landing to another.