Building Code Glossary
Air-conditioning System: Building Code Definition
How the IRC 2009, IMC 2009 define air-conditioning system, 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
Air-conditioning system is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A system that consists of heat exchangers, blowers, filters, supply, exhaust and return-air systems, and shall include any apparatus installed in connection therewith.” The IMC 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 15 chapters of this corpus, most often in Fire Protection Systems (IFC 2009), Fire Protection Systems (IBC 2009), Refrigeration (IMC 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?
Air-conditioning System — IRC 2009, Definitions:
A system that consists of heat exchangers, blowers, filters, supply, exhaust and return-air systems, and shall include any apparatus installed in connection therewith.
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Air-conditioning System, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IRC 2009 | Definitions | A system that consists of heat exchangers, blowers, filters, supply, exhaust and return-air systems, and shall include any apparatus installed in connection therewith. |
| IMC 2009 | Definitions | A system that consists of heat exchangers, blowers, filters, supply, exhaust and return ducts, and shall include any apparatus installed in connection therewith. |
Where air-conditioning system is used in the code
The term appears in 15 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Fire Protection Systems | IFC 2009 | 18 |
| Fire Protection Systems | IBC 2009 | 17 |
| Refrigeration | IMC 2009 | 4 |
| Special Detailed Requirements Based on Use and Occupancy | IBC 2009 | 3 |
| Duct Systems | IMC 2009 | 3 |
| Fire and Smoke Protection Features | IBC 2009 | 2 |
| Definitions | IMC 2009 | 2 |
| Hydronic Piping | IMC 2009 | 2 |
| Elevators and Conveying Systems | IBC 2009 | 1 |
| Structural Design | IBC 2009 | 1 |
| Fire Service Features | IFC 2009 | 1 |
| Flammable Finishes | IFC 2009 | 1 |
3 further chapters mention the term.
The term in use
How the code actually writes about air-conditioning system, quoted from the 2009 text hosted here:
Joints and all refrigerant-containing parts of a refrigerating system located in an air duct of an air-conditioning system carrying conditioned air to and from human-occupied space shall be constructed to withstand, without leakage, a pressure of 150 percent of the higher of the design pressure or pressure relief device setting.
or from the building air-conditioning system, provided it is so arranged as to provide sufficient air when other systems are not in operation.
Elevator machine rooms that contain solid-state equipment for elevator operation shall be provided with an independent ventilation or air-conditioning system to protect against the overheating of the electrical equipment.
The terms air-conditioning system 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 air-conditioning system covers:
- System — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.
- Shall — IRC 2009: The term, when used in the code, is construed as mandatory.
Air-conditioning System: 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 IRC | Definitions | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Fire Protection Systems (IFC 2009) | |
| Re-check the requirement that uses it | Fire Protection Systems (IBC 2009) | |
| Re-check the requirement that uses it | Refrigeration (IMC 2009) | |
| Re-check the requirement that uses it | Special Detailed Requirements Based on Use and Occupancy (IBC 2009) | |
| Confirm the dependent definition | System | |
| Confirm the dependent definition | Shall | |
| 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
- System: Building Code Definition
- Building: Building Code Definition
- Construction Documents: Building Code Definition
- Registered Design Professional: 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 air-conditioning system?
The International Residential Code (IRC) 2009 defines it in Definitions as: “A system that consists of heat exchangers, blowers, filters, supply, exhaust and return-air systems, and shall include any apparatus installed in connection therewith.” 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 air-conditioning system?
In this corpus the term is used across 15 chapters, led by Fire Protection Systems 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 an air conditioning system?
Air Conditioning is a separate defined term. The IMC 2009 defines it as: “The treatment of air so as to control simultaneously the temperature, humidity, cleanness and distribution of the air to meet the requirements of a conditioned space.” That is not the same as air-conditioning system, which the IRC 2009 defines as “A system that consists of heat exchangers, blowers, filters, supply, exhaust and return-air systems, and shall include any apparatus installed in connection therewith.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
What is a HVAC system in a building?
Building is a separate defined term. The IBC 2009 defines it as: “Any structure used or intended for supporting or sheltering any use or occupancy.” That is not the same as air-conditioning system, which the IRC 2009 defines as “A system that consists of heat exchangers, blowers, filters, supply, exhaust and return-air systems, and shall include any apparatus installed in connection therewith.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
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