Building Code Glossary
Relief Vent: Building Code Definition
How the IPC 2009 define relief vent, 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
Relief vent is a defined term in the International Plumbing Code (IPC) 2009, in Definitions. The code's own words are: “A vent whose primary function is to provide circulation of air between drainage and vent systems.” No other I-Code in this corpus defines it, so the IPC 2009 definition is the one to work from. The term is used in 9 chapters of this corpus, most often in Vents (IPC 2009), Exhaust Systems (IMC 2009), Fuel Gas (IRC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted. Record the jurisdiction, the adopted edition, the application date and any local amendment that rewrites the definition before you use it on a live project, because a term redefined by amendment changes every requirement that depends on it.
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?
Relief Vent — IPC 2009, Definitions:
A vent whose primary function is to provide circulation of air between drainage and vent systems.
What must be verified before using this guidance?
Relief Vent is defined once in this corpus, in the Definitions chapter of the International Plumbing Code (IPC) 2009:
A vent whose primary function is to provide circulation of air between drainage and vent systems.
Where relief vent is used in the code
The term appears in 9 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Vents | IPC 2009 | 22 |
| Exhaust Systems | IMC 2009 | 10 |
| Fuel Gas | IRC 2009 | 7 |
| Motor Fuel-dispensing Facilities and Repair Garages | IFC 2009 | 6 |
| Flammable and Combustible Liquids | IFC 2009 | 4 |
| Traps, Interceptors and Separators | IPC 2009 | 4 |
| Compressed Gases | IFC 2009 | 2 |
| Definitions | IPC 2009 | 1 |
| Vents | IRC 2009 | 1 |
The term in use
How the code actually writes about relief vent, quoted from the 2009 text hosted here:
A relief vent shall be provided for circuit-vented horizontal branches receiving the discharge of four or more water closets and connecting to a drainage stack that receives the discharge of soil or waste from upper horizontal branches.
A safety or explosion relief vent shall be provided on all systems that convey combustible refuse or stock of an explosive nature, in accordance with the requirements of the International Building Code.
Building traps shall be provided with a cleanout and a relief vent or fresh air intake on the inlet side of the trap.
The terms relief vent is built out of
The definition above leans on 1 other defined term. Each carries its own code definition, and a local amendment to any of them changes what relief vent covers:
- Primary Function — IBC 2009: A primary function is a major activity for which the facility is intended.
Relief Vent: 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 IPC | Definitions | |
| Re-check the requirement that uses it | Vents (IPC 2009) | |
| Re-check the requirement that uses it | Exhaust Systems (IMC 2009) | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Re-check the requirement that uses it | Motor Fuel-dispensing Facilities and Repair Garages (IFC 2009) | |
| Confirm the dependent definition | Primary Function | |
| 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
- Primary Function: 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 relief vent?
The International Plumbing Code (IPC) 2009 defines it in Definitions as: “A vent whose primary function is to provide circulation of air between drainage and vent systems.” 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 relief vent?
In this corpus the term is used across 9 chapters, led by Vents in the IPC 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 are the building code requirements for venting in Florida?
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 relief vent, which the IPC 2009 defines as “A vent whose primary function is to provide circulation of air between drainage and vent systems.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
What are the rules for venting a toilet?
Venting is a separate defined term. The IRC 2009 defines it as: “Removal of combustion products to the outdoors.” That is not the same as relief vent, which the IPC 2009 defines as “A vent whose primary function is to provide circulation of air between drainage and vent systems.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
What is a relief vent in plumbing?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IPC 2009 states, in Definitions: “A vent whose primary function is to provide circulation of air between drainage and vent systems.” It is defined in IPC 2009. It is not the same as Plumbing, which the IRC 2009 defines separately as “For the purpose of this code, plumbing refers to those installations, repairs, maintenance and alterations regulated by Chapters 25 through 33.” 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.
Related pages
- Relief Opening: Building Code Definition
Relief Opening — IRC 2009 definition: The opening provided in a drafthoodto permit the ready escape to the atmosphere of the flue …
- Relief Valve, Pressure: Building Code Definition
Relief Valve, Pressure — IRC 2009 definition: An automatic valve which opens and closes a relief vent, depending on whether the pressure is …
- Relief Valve, Vacuum: Building Code Definition
Relief Valve, Vacuum — IRC 2009 definition: A valve that automatically opens and closes a vent for relieving a vacuum within the hot …
- Religious Worship, Place OF: Building Code Definition
Religious Worship, Place OF — IBC 2009 definition: A building or portion thereof intended for the performance of religious services.
- Remote Solvent Reservoir: Building Code Definition
Remote Solvent Reservoir — IFC 2009 definition: A liquid solvent container enclosed against evaporative losses to the atmosphere during periods when the container …
- Repair Garage: Building Code Definition
Repair Garage — IFC 2009 definition: A building, structure or portion thereof used for servicing or repairing motor vehicles.