# Pressure Vessels: Building Code Definition > How the IMC 2009 define pressure vessels, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/pressure-vessels/ - 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 | 8 (counted across the codes hosted here) | | Wording identical across codes | Single code (compare before citing one code's wording under another) | ## Direct answer Pressure vessels is a defined term in the International Mechanical Code (IMC) 2009, in Definitions. The code's own words are: “Closed containers, tanks or vessels that are designed to contain liquids or gases, or both, under pressure.” 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 8 chapters of this corpus, most often in Boilers, Water Heaters and Pressure Vessels (IMC 2009), Flammable and Combustible Liquids (IFC 2009), Flammable Finishes (IFC 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 Vessels** — IMC 2009, Definitions: > Closed containers, tanks or vessels that are designed to contain liquids or gases, or both, under pressure. ![Labeled code-term definition diagram: Pressure Vessels: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/pressure-vessels/diagram-1344.webp) *How the IMC 2009 define pressure vessels, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? **Pressure Vessels** 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: > Closed containers, tanks or vessels that are designed to contain liquids or gases, or both, under pressure. ## Where pressure vessels is used in the code The term appears in 8 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [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 | 21 | | [Flammable and Combustible Liquids](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-and-combustible-liquids.md) | IFC 2009 | 10 | | [Flammable Finishes](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-finishes.md) | IFC 2009 | 2 | | [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 | | [Hazardous Materials-general Provisions](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/hazardous-materials-general-provisions.md) | IFC 2009 | 2 | | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 2 | | [Hydronic Piping](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/hydronic-piping.md) | IMC 2009 | 2 | | [Refrigeration](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/refrigeration.md) | IMC 2009 | 1 | ### The term in use How the code actually writes about pressure vessels, quoted from the 2009 text hosted here: > This chapter shall govern the installation, alteration and repair of boilers, water heaters and pressure vessels. — [IMC 2009 §1001.1](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/boilers-water-heaters-and-pressure-vessels.md) > and piping in connection with boilers and pressure vessels regulated by the International Mechanical Code. — [IFC 2009 §3403.6.1](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-and-combustible-liquids.md) > Separate pressure vessels and inserts specifically for the application shall be used for the resin and for the organic peroxide, and shall not be interchanged. — [IFC 2009 §1508.3.1](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/flammable-finishes.md) ## Pressure Vessels: 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 | Boilers, Water Heaters and Pressure Vessels (IMC 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) | | | Re-check the requirement that uses it | Flammable Gases and Flammable Cryogenic Fluids (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](https://harth.build/resources/glossary.md) - [Building: Building Code Definition](https://harth.build/resources/glossary/building.md) - [Construction Documents: Building Code Definition](https://harth.build/resources/glossary/construction-documents.md) - [Registered Design Professional: Building Code Definition](https://harth.build/resources/glossary/registered-design-professional.md) - [Dwelling Unit: Building Code Definition](https://harth.build/resources/glossary/dwelling-unit.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 vessels? The International Mechanical Code (IMC) 2009 defines it in Definitions as: “Closed containers, tanks or vessels that are designed to contain liquids or gases, or both, under pressure.” 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 vessels? In this corpus the term is used across 8 chapters, led by Boilers, Water Heaters and Pressure Vessels 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 is the code for pressure vessels? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IMC 2009 states, in Definitions: “Closed containers, tanks or vessels that are designed to contain liquids or gases, or both, under pressure.” 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. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fpressure-vessels%2F - View this page in a browser: https://harth.build/resources/glossary/pressure-vessels/ - All resources for agents: https://harth.build/llms.txt