# Offset (Vent): Building Code Definition

> How the IRC 2009, IMC 2009 define offset (vent), where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/offset-vent/
- 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 | IRC 2009, IMC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IRC 2009 Fuel Gas (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 2 (counted across the codes hosted here) |
| Wording identical across codes | Yes (compare before citing one code's wording under another) |

## Direct answer

Offset (vent) is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “A combination of approved bends that make two changes in direction bringing one section of the vent out of line, but into a line parallel with the other section.” The IMC 2009 carries the same definition word for word, so the term means the same thing in each. The term is used in 2 chapters of this corpus, most often in Definitions (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](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?

**Offset (Vent)** — IRC 2009, Fuel Gas:

> A combination of approved bends that make two changes in direction bringing one section of the vent out of line, but into a line parallel with the other section.

![Labeled code-term definition diagram: Offset (Vent): Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/offset-vent/diagram-1344.webp)

*How the IRC 2009, IMC 2009 define offset (vent), where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

Two of the I-Codes in this corpus define **Offset (Vent)**, in identical words.

| Code | Where it is defined | Definition |
| --- | --- | --- |
| IRC 2009 | [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | A combination of approved bends that make two changes in direction bringing one section of the vent out of line, but into a line parallel with the other section. |
| IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | A combination of approved bends that make two changes in direction bringing one section of the vent out of line but into a line parallel with the other section. |

## Where offset (vent) 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/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 1 |
| [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 1 |

## Offset (Vent) compared with Offset

These two are the closest pair in the 2009 I-Codes: about 81 per cent of their defining words are the same. The code states both and compares neither, so the difference is worth naming.

| | Wording unique to it |
| --- | --- |
| **Offset (Vent)** (IRC 2009) | approved, bends, make, vent |
| [Offset](https://harth.build/resources/glossary/offset.md) (IRC 2009) | fittings, makes, pipe |

Everything else in the two definitions is shared. If a project turns on which of the two applies, those words are the whole of the test — and a local amendment that edits one of them without editing the other moves the boundary between offset (vent) and offset.

## The terms offset (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 offset (vent) covers:

- **[Approved](https://harth.build/resources/glossary/approved.md)** — IBC 2009: Acceptable to the code official or authority having jurisdiction.

## Offset (Vent): 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 IRC | Fuel Gas | |
| Read the definition in the adopted IMC | Definitions | |
| Re-check the requirement that uses it | Definitions (IMC 2009) | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Confirm the dependent definition | Approved | |
| 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)
- [Approved: Building Code Definition](https://harth.build/resources/glossary/approved.md)
- [Code Official: Building Code Definition](https://harth.build/resources/glossary/code-official.md)
- [Code: Building Code Definition](https://harth.build/resources/glossary/code.md)
- [Fuel Gas: Building Code Definition](https://harth.build/resources/glossary/fuel-gas.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 offset (vent)?

The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “A combination of approved bends that make two changes in direction bringing one section of the vent out of line, but into a line parallel with the other section.” 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 offset (vent)?

In this corpus the term is used across 2 chapters, led by Definitions in the IMC 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 offset (vent), which the IRC 2009 defines as “A combination of approved bends that make two changes in direction bringing one section of the vent out of line, but into a line parallel with the other section.” — 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 offset (vent), which the IRC 2009 defines as “A combination of approved bends that make two changes in direction bringing one section of the vent out of line, but into a line parallel with the other section.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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