# Absorption System: Building Code Definition

> How the IMC 2009 define absorption system, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/absorption-system/
- 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 | 6 (counted across the codes hosted here) |
| Wording identical across codes | Single code (compare before citing one code's wording under another) |

## Direct answer

Absorption system is a defined term in the International Mechanical Code (IMC) 2009, in Definitions. The code's own words are: “A refrigerating system in which refrigerant is pressurized by pumping a chemical solution of refrigerant in absorbent, and then separated by the addition of heat in a generator, condensed (to reject heat), expanded, evaporated (to provide refrigeration), and reabsorbed in an absorber to repeat the cycle; the system may be single or multiple effect, the …” 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 6 chapters of this corpus, most often in Site Evaluation and Requirements (IPC 2009), Soil Absorption Systems (IPC 2009), Building Services and Systems (IFC 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?

**Absorption System** — IMC 2009, Definitions:

> A refrigerating system in which refrigerant is pressurized by pumping a chemical solution of refrigerant in absorbent, and then separated by the addition of heat in a generator, condensed (to reject heat), expanded, evaporated (to provide refrigeration), and reabsorbed in an absorber to repeat the cycle; the system may be single or multiple effect, the latter using multiple stages or internally cascaded use of heat to improve efficiency.

## What must be verified before using this guidance?

**Absorption System** 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 refrigerating system in which refrigerant is pressurized by pumping a chemical solution of refrigerant in absorbent, and then separated by the addition of heat in a generator, condensed (to reject heat), expanded, evaporated (to provide refrigeration), and reabsorbed in an absorber to repeat the cycle; the system may be single or multiple effect, the latter using multiple stages or internally cascaded use of heat to improve efficiency.

## Where absorption system 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 |
| --- | --- | --- |
| [Site Evaluation and Requirements](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/site-evaluation-and-requirements.md) | IPC 2009 | 34 |
| [Soil Absorption Systems](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/soil-absorption-systems.md) | IPC 2009 | 17 |
| [Building Services and Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/building-services-and-systems.md) | IFC 2009 | 3 |
| [Tanks](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/tanks.md) | IPC 2009 | 2 |
| [Heating and Cooling Equipment](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/heating-and-cooling-equipment.md) | IRC 2009 | 2 |
| [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 1 |

### The term in use

How the code actually writes about absorption system, quoted from the 2009 text hosted here:

> A conventional soil absorption system shall not be located on land with a slope greater than 20 percent.

— [IPC 2009 §402.1](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/site-evaluation-and-requirements.md)

> A pressure distribution system shall be permitted in place ofa conventional or dosing conventional soil absorption system where a site is suitable for a conventional private sewage disposal system.

— [IPC 2009 §602.2](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/soil-absorption-systems.md)

> Where the total developed length of distribution piping exceeds 1,000 feet (305 m), the dosing or pumping chamber shall have two siphons or pumps dosing alternately and serving one-half of the soil absorption system.

— [IPC 2009 §802.11.1](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/tanks.md)


## The terms absorption system is built out of

The definition above leans on 5 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what absorption system covers:

- **[Refrigerating System](https://harth.build/resources/glossary/refrigerating-system.md)** — IRC 2009: A combination of interconnected parts forming a closed circuit in which refrigerant is circulated for the purpose of extracting, then rejecting, heat.
- **[Refrigerant](https://harth.build/resources/glossary/refrigerant.md)** — IRC 2009: A substance used to produce refrigeration by its expansion or evaporation.
- **[Addition](https://harth.build/resources/glossary/addition.md)** — IBC 2009: An extension or increase in floor area or height of a building or structure.
- **[Chemical](https://harth.build/resources/glossary/chemical.md)** — IFC 2009: An element, chemical compound or mixture of elements or compounds or both.
- **[System](https://harth.build/resources/glossary/system.md)** — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping.

## Absorption System: 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 | Site Evaluation and Requirements (IPC 2009) | |
| Re-check the requirement that uses it | Soil Absorption Systems (IPC 2009) | |
| Re-check the requirement that uses it | Building Services and Systems (IFC 2009) | |
| Re-check the requirement that uses it | Tanks (IPC 2009) | |
| Confirm the dependent definition | Refrigerating System | |
| Confirm the dependent definition | Refrigerant | |
| Confirm the dependent definition | Addition | |
| 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)
- [Refrigerating System: Building Code Definition](https://harth.build/resources/glossary/refrigerating-system.md)
- [Refrigerant: Building Code Definition](https://harth.build/resources/glossary/refrigerant.md)
- [Chemical: Building Code Definition](https://harth.build/resources/glossary/chemical.md)
- [Addition: Building Code Definition](https://harth.build/resources/glossary/addition.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 absorption system?

The International Mechanical Code (IMC) 2009 defines it in Definitions as: “A refrigerating system in which refrigerant is pressurized by pumping a chemical solution of refrigerant in absorbent, and then separated by the addition of heat in a generator, condensed (to reject heat), expanded, evaporated (to provide refrigeration), and reabsorbed in an absorber to repeat the cycle; the system may be single or multiple effect, the latter using multiple stages or internally cascaded use of heat to improve efficiency.” 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 absorption system?

In this corpus the term is used across 6 chapters, led by Site Evaluation and Requirements in the IPC 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.

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