Building Code Glossary
Purge: Building Code Definition
How the IRC 2009, IMC 2009 define purge, 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
Purge is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “To clear of air, gas or other foreign substances.” The IMC 2009 words it differently, in Definitions: “To clear of air, water or other foreign substances.” 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 11 chapters of this corpus, most often in Motor Fuel-dispensing Facilities and Repair Garages (IFC 2009), Fuel Gas (IRC 2009), Flammable and Combustible Liquids (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?
Purge — IRC 2009, Definitions:
To clear of air, gas or other foreign substances.
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Purge, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IRC 2009 | Definitions | To clear of air, gas or other foreign substances. |
| IMC 2009 | Definitions | To clear of air, water or other foreign substances. |
Where purge is used in the code
The term appears in 11 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Motor Fuel-dispensing Facilities and Repair Garages | IFC 2009 | 12 |
| Fuel Gas | IRC 2009 | 8 |
| Flammable and Combustible Liquids | IFC 2009 | 4 |
| Flammable Finishes | IFC 2009 | 4 |
| Water Supply and Distribution | IPC 2009 | 4 |
| Industrial Ovens | IFC 2009 | 2 |
| Welding and Other Hot Work | IFC 2009 | 2 |
| Building Services and Systems | IFC 2009 | 1 |
| Definitions | IMC 2009 | 1 |
| Refrigeration | IMC 2009 | 1 |
| Definitions | IRC 2009 | 1 |
The term in use
How the code actually writes about purge, quoted from the 2009 text hosted here:
The maximum flow rate shall be determined in accordance with the requirements of CGA S-1.3 using the aggregate gas flow rate from all connected vent, purge and relief devices that operate simultaneously during a venting operation, purging operation or emergency relief event.
Pressure relief devices, fusible plugs and purge systems located within the machinery room shall terminate outside of the structure at a location not less than 15 feet (4572 mm) above the adjoining grade level and not less than 20 feet (6096 mm) from any window, ventilation opening or exit.
Purge: 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 | Motor Fuel-dispensing Facilities and Repair Garages (IFC 2009) | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Re-check the requirement that uses it | Flammable and Combustible Liquids (IFC 2009) | |
| Re-check the requirement that uses it | Flammable Finishes (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
- Building: Building Code Definition
- Construction Documents: Building Code Definition
- Registered Design Professional: Building Code Definition
- Dwelling Unit: 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 purge?
The International Residential Code (IRC) 2009 defines it in Definitions as: “To clear of air, gas or other foreign substances.” 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 purge?
In this corpus the term is used across 11 chapters, led by Motor Fuel-dispensing Facilities and Repair Garages 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 a smoke purge system?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “To clear of air, gas or other foreign substances.” It is defined in IRC 2009, IMC 2009. It is not the same as System, which the IFC 2009 defines separately as “An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.” Because it is a defined term, whatever the adopted edition says it means is what every section using it means — so check Chapter 2 of that edition and any local amendment before relying on this wording.
What is purge from cache?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “To clear of air, gas or other foreign substances.” It is defined in IRC 2009, IMC 2009. Because it is a defined term, whatever the adopted edition says it means is what every section using it means — so check Chapter 2 of that edition and any local amendment before relying on this wording.
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