# Direct-vent Appliances: Building Code Definition > How the IRC 2009, IMC 2009 define direct-vent appliances, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/direct-vent-appliances/ - 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 | 7 (counted across the codes hosted here) | | Wording identical across codes | No (compare before citing one code's wording under another) | ## Direct answer Direct-vent appliances is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “Appliances that are constructed and installed so that all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged directly to the outside atmosphere.” The IMC 2009 defines the same term with different wording, so the controlling text depends on which code governs the question in front of you — the comparison below sets the versions side by side. The term is used in 7 chapters of this corpus, most often in Fuel Gas (IRC 2009), Chimneys and Vents (IRC 2009), General Regulations (IMC 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? **Direct-vent Appliances** — IRC 2009, Fuel Gas: > Appliances that are constructed and installed so that all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged directly to the outside atmosphere. ![Labeled code-term definition diagram: Direct-vent Appliances: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/direct-vent-appliances/diagram-1344.webp) *How the IRC 2009, IMC 2009 define direct-vent appliances, 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 **Direct-vent Appliances**, and the wording is not identical — read the version that governs your question. | Code | Where it is defined | Definition | | --- | --- | --- | | IRC 2009 | [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | Appliances that are constructed and installed so that all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged directly to the outside atmosphere. | | IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | Appliances that are constructed and installed so that all air for combustion is derived from the outdoor atmosphere and all flue gases are discharged to the outdoor atmosphere. | ## Where direct-vent appliances is used in the code The term appears in 7 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 | 13 | | [Chimneys and Vents](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/chimneys-and-vents.md) | IRC 2009 | 4 | | [General Regulations](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/general-regulations.md) | IMC 2009 | 2 | | [Chimneys and Vents](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/chimneys-and-vents.md) | IMC 2009 | 1 | | [Combustion Air](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/combustion-air.md) | IMC 2009 | 1 | | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 1 | | [Combustion Air](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/combustion-air.md) | IRC 2009 | 1 | ### The term in use How the code actually writes about direct-vent appliances, quoted from the 2009 text hosted here: > Direct-vent appliances, gas appliances of other than natural draft design and vented gas appliances other than Category I shall be provided with combustion, ventilation and dilution air in accordance with the appliance manufacturer's instructions. — [IRC 2009 §G2407.1](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) > Direct-vent appliances shall be installed in accordance with the manufacturer's installation instructions. — [IRC 2009 §M1801.6](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/chimneys-and-vents.md) > The methods of providing combustion air in this chapter do not apply to fireplaces, fireplace stoves and direct-vent appliances. — [IMC 2009 §701.1](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/combustion-air.md) ## The terms direct-vent appliances 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 direct-vent appliances covers: - **[Combustion](https://harth.build/resources/glossary/combustion.md)** — IRC 2009: In the context of this code, refers to the rapid oxidation of fuel accompanied by the production of heat or heat and light. - **[Flue Gases](https://harth.build/resources/glossary/flue-gases.md)** — IRC 2009: Products of combustion plus excess air in appliance flues or heat exchangers. ## Direct-vent Appliances: 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 | Fuel Gas (IRC 2009) | | | Re-check the requirement that uses it | Chimneys and Vents (IRC 2009) | | | Re-check the requirement that uses it | General Regulations (IMC 2009) | | | Re-check the requirement that uses it | Chimneys and Vents (IMC 2009) | | | Confirm the dependent definition | Combustion | | | Confirm the dependent definition | Flue Gases | | | 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) - [Flue Gases: Building Code Definition](https://harth.build/resources/glossary/flue-gases.md) - [Combustion: Building Code Definition](https://harth.build/resources/glossary/combustion.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 direct-vent appliances? The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “Appliances that are constructed and installed so that all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged directly to the outside atmosphere.” 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 direct-vent appliances? In this corpus the term is used across 7 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. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fdirect-vent-appliances%2F - View this page in a browser: https://harth.build/resources/glossary/direct-vent-appliances/ - All resources for agents: https://harth.build/llms.txt