Building Code Glossary
Furnace Class A: Building Code Definition
How the IFC 2009 define furnace class a, 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
Furnace class A 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 has heat utilization equipment operating at approximately atmospheric pressure wherein there is a potential explosion or fire hazard that could be occasioned by the presence of flammable volatiles or combustible materials processed or heated in the furnace.” 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, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Furnace Class A — IFC 2009, Industrial Ovens:
An oven or furnace that has heat utilization equipment operating at approximately atmospheric pressure wherein there is a potential explosion or fire hazard that could be occasioned by the presence of flammable volatiles or combustible materials processed or heated in the furnace.
What must be verified before using this guidance?
Furnace Class A is defined once in this corpus, in the Industrial Ovens chapter of the International Fire Code (IFC) 2009:
An oven or furnace that has heat utilization equipment operating at approximately atmospheric pressure wherein there is a potential explosion or fire hazard that could be occasioned by the presence of flammable volatiles or combustible materials processed or heated in the furnace.
Where furnace class a 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 | IFC 2009 | 1 |
| Industrial Ovens | IFC 2009 | 1 |
The terms furnace class A is built out of
The definition above leans on 5 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what furnace class A covers:
- Utilization Equipment — IRC 2009: Equipment that utilizes electric energy for electronic, electromechanical, chemical, heating' lighting or similar purposes.
- Atmospheric Pressure — IRC 2009: The pressure of the weight of air and water vapor on the surface of the earth, approximately 14.7 pounds per square inch (psia) (101 kPa absolute) at sea level.
- Equipment — IRC 2009: All piping, ducts, vents, control devices and other components of systems other than appliances that are permanently installed and integrated to provide control of environmental conditions for buildings.
- Explosion — IBC 2009: An effect produced by the sudden violent expansion of gases, which may be accompanied by a shock wave or disruption, or both, of enclosing materials or structures.
- Furnace — 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.
Furnace Class A: 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 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 | Utilization Equipment | |
| Confirm the dependent definition | Atmospheric Pressure | |
| Confirm the dependent definition | Equipment | |
| 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
- Utilization Equipment: Building Code Definition
- Atmospheric Pressure: Building Code Definition
- Explosion: Building Code Definition
- Equipment: 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 furnace class a?
The International Fire Code (IFC) 2009 defines it in Industrial Ovens as: “An oven or furnace that has heat utilization equipment operating at approximately atmospheric pressure wherein there is a potential explosion or fire hazard that could be occasioned by the presence of flammable volatiles or combustible materials processed or heated in the furnace.” 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 a?
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.
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