# Air-handling Unit: Building Code Definition > How the IRC 2009, IMC 2009 define air-handling unit, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/air-handling-unit/ - 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 | 6 (counted across the codes hosted here) | | Wording identical across codes | Yes (compare before citing one code's wording under another) | ## Direct answer Air-handling unit is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “A blower or fan used for the purpose of distributing supply air to a room, space or area.” The IMC 2009 carries the same definition word for word, so the term means the same thing in each. The term is used in 6 chapters of this corpus, most often in Ventilation (IMC 2009), Definitions (IMC 2009), Duct Systems (IMC 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? **Air-handling Unit** — IRC 2009, Fuel Gas: > A blower or fan used for the purpose of distributing supply air to a room, space or area. ![Labeled code-term definition diagram: Air-handling Unit: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/air-handling-unit/diagram-1344.webp) *How the IRC 2009, IMC 2009 define air-handling unit, 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 **Air-handling Unit**, 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 blower or fan used for the purpose of distributing supply air to a room, space or area. | | IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | A blower or fan used for the purpose of distributing supply air to a room, space or area. | ## Where air-handling unit is used in the code The term appears in 6 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [Ventilation](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/ventilation.md) | IMC 2009 | 6 | | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 2 | | [Duct Systems](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/duct-systems.md) | IMC 2009 | 2 | | [Means of Egress](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/means-of-egress.md) | IBC 2009 | 1 | | [Means of Egress](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/means-of-egress.md) | IFC 2009 | 1 | | [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 1 | ### The term in use How the code actually writes about air-handling unit, quoted from the 2009 text hosted here: > Vpz = Primary airflow: The airflow rate supplied to the zone from the air-handling unit at which the outdoor air intake is located. — [IMC 2009, Ventilation](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/ventilation.md) ## The terms air-handling unit 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 air-handling unit covers: - **[Supply Air](https://harth.build/resources/glossary/supply-air.md)** — IRC 2009: Air delivered to a conditioned space through ducts or plenums from the heat exchanger of a heating, cooling or ventilating system. ## Air-handling Unit: 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 | Ventilation (IMC 2009) | | | Re-check the requirement that uses it | Definitions (IMC 2009) | | | Re-check the requirement that uses it | Duct Systems (IMC 2009) | | | Re-check the requirement that uses it | Means of Egress (IBC 2009) | | | Confirm the dependent definition | Supply Air | | | 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) - [Supply Air: Building Code Definition](https://harth.build/resources/glossary/supply-air.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 air-handling unit? The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “A blower or fan used for the purpose of distributing supply air to a room, space or area.” 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 air-handling unit? In this corpus the term is used across 6 chapters, led by Ventilation 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 function of an air handling unit in a building? 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 air-handling unit, which the IRC 2009 defines as “A blower or fan used for the purpose of distributing supply air to a room, space or area.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted. ### What is the difference between an air handling unit and an air conditioning unit? Air Conditioning is a separate defined term. The IMC 2009 defines it as: “The treatment of air so as to control simultaneously the temperature, humidity, cleanness and distribution of the air to meet the requirements of a conditioned space.” That is not the same as air-handling unit, which the IRC 2009 defines as “A blower or fan used for the purpose of distributing supply air to a room, space or area.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fair-handling-unit%2F - View this page in a browser: https://harth.build/resources/glossary/air-handling-unit/ - All resources for agents: https://harth.build/llms.txt