# Relief Opening: Building Code Definition

> How the IRC 2009 define relief opening, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/relief-opening/
- 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 (2009 editions transcribed in this corpus) |
| Primary source | IRC 2009 Fuel Gas (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 4 (counted across the codes hosted here) |
| Wording identical across codes | Single code (compare before citing one code's wording under another) |

## Direct answer

Relief opening is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “The opening provided in a drafthoodto permit the ready escape to the atmosphere of the flue products from the draft hood in the event of no draft, backdraft or stoppage beyond the draft hood, and to permit air into the draft hood in the event of a strong chimney updraft.” No other I-Code in this corpus defines it, so the IRC 2009 definition is the one to work from. The term is used in 4 chapters of this corpus, most often in Fuel Gas (IRC 2009), Water Supply and Distribution (IPC 2009), Water Supply and Distribution (IRC 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](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?

**Relief Opening** — IRC 2009, Fuel Gas:

> The opening provided in a drafthoodto permit the ready escape to the atmosphere of the flue products from the draft hood in the event of no draft, backdraft or stoppage beyond the draft hood, and to permit air into the draft hood in the event of a strong chimney updraft.

![Labeled code-term definition diagram: Relief Opening: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/relief-opening/diagram-1344.webp)

*How the IRC 2009 define relief opening, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

**Relief Opening** is defined once in this corpus, in the [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) chapter of the International Residential Code (IRC) 2009:

> The opening provided in a drafthoodto permit the ready escape to the atmosphere of the flue products from the draft hood in the event of no draft, backdraft or stoppage beyond the draft hood, and to permit air into the draft hood in the event of a strong chimney updraft.

## Where relief opening is used in the code

The term appears in 4 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 5 |
| [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-supply-and-distribution.md) | IPC 2009 | 4 |
| [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-supply-and-distribution.md) | IRC 2009 | 4 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-protection-systems.md) | IBC 2009 | 3 |

### The term in use

How the code actually writes about relief opening, quoted from the 2009 text hosted here:

> Draft hoods and draft regulators shall be installed in the position for which they were designed with reference to the horizontal and vertical planes and shall be located so that the relief opening is not obstructed by any part of the appliance or adjacent construction.

— [IRC 2009 §G2427.12.6](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md)

> The relief opening shall discharge by air gap and shall be prevented from being submerged.

— [IPC 2009 §608.13.2](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-supply-and-distribution.md)

> The stair shaft shall be provided with a dampered relief opening and supplied with sufficient air to maintain a minimum positive pressure of 0.10 inch of water (25 Pa) in the shaft relative to the vestibule with all doors closed.

— [IBC 2009 §909.20.4.4](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-protection-systems.md)


## The terms relief opening is built out of

The definition above leans on 4 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what relief opening covers:

- **[Draft Hood](https://harth.build/resources/glossary/draft-hood.md)** — IRC 2009: A nonadjustable device built into an appliance, or made as part of the vent connector from an appliance, that is designed to (1) provide for ready escape of the flue gases from the appliance in the event of no draft …
- **[Chimney](https://harth.build/resources/glossary/chimney.md)** — IBC 2009: A primarily vertical enclosure containing one or more passageways for conveying flue gases to the outside atmosphere.
- **[Permit](https://harth.build/resources/glossary/permit.md)** — IBC 2009: An official document or certificate issued by the authority having jurisdiction which authorizes performance of a specified activity.
- **[Draft](https://harth.build/resources/glossary/draft.md)** — IRC 2009: The pressure difference existing between the appliance or any component part and the atmosphere, that causes a continuous flow of air and products of combustion through the gas passages of the appliance to the atmosphere.

## Relief Opening: 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 | |
| Re-check the requirement that uses it | Fuel Gas (IRC 2009) | |
| Re-check the requirement that uses it | Water Supply and Distribution (IPC 2009) | |
| Re-check the requirement that uses it | Water Supply and Distribution (IRC 2009) | |
| Re-check the requirement that uses it | Fire Protection Systems (IBC 2009) | |
| Confirm the dependent definition | Draft Hood | |
| Confirm the dependent definition | Chimney | |
| Confirm the dependent definition | Permit | |
| 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)
- [Draft Hood: Building Code Definition](https://harth.build/resources/glossary/draft-hood.md)
- [Chimney: Building Code Definition](https://harth.build/resources/glossary/chimney.md)
- [Permit: Building Code Definition](https://harth.build/resources/glossary/permit.md)
- [Draft: Building Code Definition](https://harth.build/resources/glossary/draft.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 relief opening?

The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “The opening provided in a drafthoodto permit the ready escape to the atmosphere of the flue products from the draft hood in the event of no draft, backdraft or stoppage beyond the draft hood, and to permit air into the draft hood in the event of a strong chimney updraft.” 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 opening?

In this corpus the term is used across 4 chapters, led by Fuel Gas in the IRC 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 does IRC mean in building code?

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 opening, which the IRC 2009 defines as “The opening provided in a drafthoodto permit the ready escape to the atmosphere of the flue products from the draft hood in the event of no draft, backdraft or stoppage beyond the draft hood, and to permit air into the …” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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