ASHRAE Terminology

A Comprehensive Glossary of Terms for the Built Environment
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air diffusion

(1) distribution of the air in a space, called the treated space, in a manner to satisfy certain specified conditions such as air change rate, pressure, cleanliness, temperature, humidity, air velocity, and noise level, in a specified zone within this treated space, which is called the occupied zone. It is usually achieved by means of air terminal devices which form the common boundaries between the treated space and the air-distribution system. (2) the introduction of air into a building space for the purpose of providing acceptable velocity and temperature distribution in the occupied zone.

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About ASHRAE Terminology

ASHRAE Terminology, a free resource, is a comprehensive online glossary of more than 3700 terms and definitions related to the built environment, with a focus on heating, ventilating, and air conditioning (HVAC), as well as refrigeration, building envelope, electrical, lighting, water and energy use, and measurement terms.

This searchable glossary was designed for use by engineering professionals but is also useful for architects, building owners and operators, educators, public officials, and homeowners.

The terms in ASHRAE Terminology have been assembled and defined and are updated on an ongoing basis by ASHRAE Technical Committee (TC) 1.6, Terminology. TC 1.6 is concerned with terminology, nomenclature, definitions, abbreviations, symbols, and the International System (SI) and Inch-Pound (I-P) units used in the fields of heating, ventilating, air conditioning, water heating, and refrigeration.

To request a free electronic file of the complete list of terms and definitions, email ashraetermseditor@ashrae.org.