# Pressure Relief Valve: Building Code Definition

> How the IMC 2009 define pressure relief valve, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/pressure-relief-valve/
- 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 | IMC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IMC 2009 Definitions (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 12 (counted across the codes hosted here) |
| Wording identical across codes | Single code (compare before citing one code's wording under another) |

## Direct answer

Pressure relief valve is a defined term in the International Mechanical Code (IMC) 2009, in Definitions. The code's own words are: “A pressure-actuated valve held closed by a spring or other means and designed to relieve pressure automatically in excess of the device's setting.” No other I-Code in this corpus defines it, so the IMC 2009 definition is the one to work from. The term is used in 12 chapters of this corpus, most often in Cryogenic Fluids (IFC 2009), Motor Fuel-dispensing Facilities and Repair Garages (IFC 2009), Definitions (IPC 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?

**Pressure Relief Valve** — IMC 2009, Definitions:

> A pressure-actuated valve held closed by a spring or other means and designed to relieve pressure automatically in excess of the device's setting.

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

*How the IMC 2009 define pressure relief valve, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

**Pressure Relief Valve** is defined once in this corpus, in the [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) chapter of the International Mechanical Code (IMC) 2009:

> A pressure-actuated valve held closed by a spring or other means and designed to relieve pressure automatically in excess of the device's setting.

## Where pressure relief valve is used in the code

The term appears in 12 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Cryogenic Fluids](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/cryogenic-fluids.md) | IFC 2009 | 4 |
| [Motor Fuel-dispensing Facilities and Repair Garages](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/motor-fuel-dispensing-facilities-and-repair-garages.md) | IFC 2009 | 4 |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/definitions.md) | IPC 2009 | 4 |
| [Water Heaters](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-heaters.md) | IPC 2009 | 4 |
| [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-supply-and-distribution.md) | IPC 2009 | 4 |
| [Flammable Gases and Flammable Cryogenic Fluids](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-gases-and-flammable-cryogenic-fluids.md) | IFC 2009 | 2 |
| [Liquefied Petroleum Gases](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/liquefied-petroleum-gases.md) | IFC 2009 | 2 |
| [Boilers, Water Heaters and Pressure Vessels](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/boilers-water-heaters-and-pressure-vessels.md) | IMC 2009 | 2 |
| [Refrigeration](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/refrigeration.md) | IMC 2009 | 2 |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 1 |
| [Hydronic Piping](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/hydronic-piping.md) | IMC 2009 | 1 |
| [Water Heaters](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-heaters.md) | IRC 2009 | 1 |

### The term in use

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

> All storage water heaters operating above atmospheric pressure shall be provided with an approved, self-closing (levered) pressure relief valve and temperature relief valve or combination thereof.

— [IPC 2009 §504.4](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-heaters.md)

> Every pressure tank in a hydropneumatic pressure booster system shall be protected with a pressure relief valve.

— [IPC 2009 §606.5.10](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-supply-and-distribution.md)

> Containers of liquefied flammable gases and flammable gases in solution shall be positioned in the upright position or positioned so that the pressure relief valve is in direct contact with the vapor space of the container.

— [IFC 2009 §3503.1.6](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-gases-and-flammable-cryogenic-fluids.md)


## Pressure Relief Valve compared with Pressure-relief Valve

These two are the closest pair in the 2009 I-Codes: about 61 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 |
| --- | --- |
| **Pressure Relief Valve** (IMC 2009) | excess, device, s, setting |
| [Pressure-relief Valve](https://harth.build/resources/glossary/pressure-relief-valve-code-term.md) (IRC 2009) | set |

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 pressure relief valve and pressure-relief valve.

## The terms pressure relief valve 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 pressure relief valve covers:

- **[Device](https://harth.build/resources/glossary/device.md)** — IRC 2009: Aunit of an electrical system that carries or controls electrical energy as it principal function.
- **[Valve](https://harth.build/resources/glossary/valve.md)** — IRC 2009: A device used in piping to control the gas supply to any section of a system of piping or to an appliance.

## Pressure Relief Valve: 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 IMC | Definitions | |
| Re-check the requirement that uses it | Cryogenic Fluids (IFC 2009) | |
| Re-check the requirement that uses it | Motor Fuel-dispensing Facilities and Repair Garages (IFC 2009) | |
| Re-check the requirement that uses it | Definitions (IPC 2009) | |
| Re-check the requirement that uses it | Water Heaters (IPC 2009) | |
| Confirm the dependent definition | Device | |
| Confirm the dependent definition | Valve | |
| 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)
- [Device: Building Code Definition](https://harth.build/resources/glossary/device.md)
- [Valve: Building Code Definition](https://harth.build/resources/glossary/valve.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 pressure relief valve?

The International Mechanical Code (IMC) 2009 defines it in Definitions as: “A pressure-actuated valve held closed by a spring or other means and designed to relieve pressure automatically in excess of the device's setting.” 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 pressure relief valve?

In this corpus the term is used across 12 chapters, led by Cryogenic Fluids 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 the purpose of a pressure relief valve?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IMC 2009 states, in Definitions: “A pressure-actuated valve held closed by a spring or other means and designed to relieve pressure automatically in excess of the device's setting.” It is defined in 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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