Building Code Glossary
Smoke-developed Index: Building Code Definition
How the IBC 2009, IRC 2009, IFC 2009, IMC 2009 define smoke-developed index, 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
Smoke-developed index is a defined term in the International Building Code (IBC) 2009, in Interior Finishes. The code's own words are: “A comparative measure, expressed as a dimensionless number, derived from measurements of smoke obscuration versus time for a material tested in accordance with ASTM E 84.” The IRC 2009, IFC 2009, IMC 2009 define 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 19 chapters of this corpus, most often in Plastic (IBC 2009), Building Planning (IRC 2009), Interior Finish, Decorative Materials and Furnishings (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?
Smoke-developed Index — IBC 2009, Interior Finishes:
A comparative measure, expressed as a dimensionless number, derived from measurements of smoke obscuration versus time for a material tested in accordance with ASTM E 84.
What must be verified before using this guidance?
Four of the I-Codes in this corpus define Smoke-developed Index, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IBC 2009 | Interior Finishes | A comparative measure, expressed as a dimensionless number, derived from measurements of smoke obscuration versus time for a material tested in accordance with ASTM E 84. |
| IRC 2009 | Definitions | A comparative measure, expressed as a dimensionless number, derived from measurements of smoke obscuration versus time for a material tested in accordance with ASTM E 84. |
| IFC 2009 | Interior Finish, Decorative Materials and Furnishings | A comparative measure, expressed as a dimensionless number, derived from measurements of smoke obscuration versus time for a material tested in accordance with ASTM E 84. |
| IMC 2009 | Definitions | A numerical value assigned to a material tested in accordance with ASTM E 84. |
Where smoke-developed index is used in the code
The term appears in 19 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Plastic | IBC 2009 | 30 |
| Building Planning | IRC 2009 | 23 |
| Interior Finish, Decorative Materials and Furnishings | IFC 2009 | 19 |
| Interior Finishes | IBC 2009 | 13 |
| Fire and Smoke Protection Features | IBC 2009 | 9 |
| Special Detailed Requirements Based on Use and Occupancy | IBC 2009 | 9 |
| Duct Systems | IMC 2009 | 7 |
| Duct Systems | IRC 2009 | 5 |
| Foundations | IRC 2009 | 5 |
| Exterior Walls | IBC 2009 | 3 |
| Hydronic Piping | IMC 2009 | 3 |
| Roof-ceiling Construction | IRC 2009 | 3 |
7 further chapters mention the term.
The term in use
How the code actually writes about smoke-developed index, quoted from the 2009 text hosted here:
Unless otherwise indicated in this section, foam plastic insulation and foam plastic cores of manufactured assemblies shall have a flame spread index of not more than 75 and a smoke-developed index of not more than 450 where tested in the maximum thickness intended for use in accordance with ASTM E 84 or UL 723.
Flame spread index and smoke-developed index for wall and ceiling finishes.
Interior finish materials shall be grouped in the following classes in accordance with their flame spread and smoke-developed index when tested in accordance with ASTM E 84.
Smoke-developed Index compared with Flame Spread Index
These two are the closest pair in the 2009 I-Codes: about 74 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 | |
|---|---|
| Smoke-developed Index (IBC 2009) | smoke, obscuration |
| Flame Spread Index (IBC 2009) | visual, spread, flame, ul, 723 |
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 smoke-developed index and flame spread index.
Smoke-developed Index: 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 | Interior Finishes | |
| Read the definition in the adopted IRC | Definitions | |
| Read the definition in the adopted IFC | Interior Finish, Decorative Materials and Furnishings | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Plastic (IBC 2009) | |
| Re-check the requirement that uses it | Building Planning (IRC 2009) | |
| Re-check the requirement that uses it | Interior Finish, Decorative Materials and Furnishings (IFC 2009) | |
| Re-check the requirement that uses it | Interior Finishes (IBC 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
- Flame Spread Index: Building Code Definition
- Trim: Building Code Definition
- Interior Finish: Building Code Definition
- Interior Wall and Ceiling Finish: 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 smoke-developed index?
The International Building Code (IBC) 2009 defines it in Interior Finishes as: “A comparative measure, expressed as a dimensionless number, derived from measurements of smoke obscuration versus time for a material tested in accordance with ASTM E 84.” 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.
Do the I-Codes define smoke-developed index the same way?
No. IBC 2009, IRC 2009, IFC 2009, IMC 2009 all define the term, but the wording is not identical, and a difference in wording can change which requirements are triggered. The comparison table above sets the versions side by side so you can read the one that governs your question.
Which parts of the code depend on smoke-developed index?
In this corpus the term is used across 19 chapters, led by Plastic 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 does a flame spread index of 25 mean?
Flame Spread Index is a separate defined term. The IBC 2009 defines it as: “A comparative measure, expressed as a dimensionless number, derived from visual measurements of the spread of flame versus time for a material tested in accordance with ASTM E 84 or UL 723.” That is not the same as smoke-developed index, which the IBC 2009 defines as “A comparative measure, expressed as a dimensionless number, derived from measurements of smoke obscuration versus time for a material tested in accordance with ASTM E 84.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
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