# Furnace Class D: Building Code Definition > How the IFC 2009 define furnace class d, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/furnace-class-d/ - 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 | IFC 2009 (2009 editions transcribed in this corpus) | | Primary source | IFC 2009 Industrial Ovens (model text, not a jurisdiction's adopted text) | | Chapters using the term | 2 (counted across the codes hosted here) | | Wording identical across codes | Single code (compare before citing one code's wording under another) | ## Direct answer Furnace class D is a defined term in the International Fire Code (IFC) 2009, in Industrial Ovens. The code's own words are: “An oven or furnace that operates at temperatures from above ambient to over 5,000°F (2760°C) and at pressures normally below atmospheric using any type of heating system. These furnaces can include the use of special processing atmospheres.” No other I-Code in this corpus defines it, so the IFC 2009 definition is the one to work from. The term is used in 2 chapters of this corpus, most often in Definitions (IFC 2009), Industrial Ovens (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? **Furnace Class D** — IFC 2009, Industrial Ovens: > An oven or furnace that operates at temperatures from above ambient to over 5,000°F (2760°C) and at pressures normally below atmospheric using any type of heating system. These furnaces can include the use of special processing atmospheres. ![Labeled code-term definition diagram: Furnace Class D: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/furnace-class-d/diagram-1344.webp) *How the IFC 2009 define furnace class d, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? **Furnace Class D** is defined once in this corpus, in the [Industrial Ovens](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/industrial-ovens.md) chapter of the International Fire Code (IFC) 2009: > An oven or furnace that operates at temperatures from above ambient to over 5,000°F (2760°C) and at pressures normally below atmospheric using any type of heating system. These furnaces can include the use of special processing atmospheres. ## Where furnace class d is used in the code The term appears in 2 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](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/definitions.md) | IFC 2009 | 1 | | [Industrial Ovens](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/industrial-ovens.md) | IFC 2009 | 1 | ## The terms furnace class D 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 furnace class D covers: - **[Furnace](https://harth.build/resources/glossary/furnace.md)** — IRC 2009: A completely self-contained heating unit that is designed to supply heated air to spaces remote from or adjacent to the appliance location. - **[System](https://harth.build/resources/glossary/system.md)** — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping. ## Furnace Class D: 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 IFC | Industrial Ovens | | | Re-check the requirement that uses it | Definitions (IFC 2009) | | | Re-check the requirement that uses it | Industrial Ovens (IFC 2009) | | | Confirm the dependent definition | Furnace | | | Confirm the dependent definition | System | | | 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) - [Furnace: Building Code Definition](https://harth.build/resources/glossary/furnace.md) - [System: Building Code Definition](https://harth.build/resources/glossary/system.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 furnace class d? The International Fire Code (IFC) 2009 defines it in Industrial Ovens as: “An oven or furnace that operates at temperatures from above ambient to over 5,000°F (2760°C) and at pressures normally below atmospheric using any type of heating system. These furnaces can include the use of special processing atmospheres.” 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 furnace class d? In this corpus the term is used across 2 chapters, led by Definitions 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. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Ffurnace-class-d%2F - View this page in a browser: https://harth.build/resources/glossary/furnace-class-d/ - All resources for agents: https://harth.build/llms.txt