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Clean Room Airflow Design Guide

This document discusses clean room classifications based on air changes per hour and average airflow velocity. Clean room classes 1-10 use unidirectional airflow with velocities ranging from 50-110 feet per minute and air changes from 300-650 per hour. Classes 1,000-100,000 use mixed airflow with velocities between 10-90 feet per minute and air changes of 10-250 per hour. Unidirectional airflow is defined as having an average velocity of 90 feet per minute plus or minus 20% and is used for classes 100 and below due to its effectiveness in particle removal through higher velocities.

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74 views1 page

Clean Room Airflow Design Guide

This document discusses clean room classifications based on air changes per hour and average airflow velocity. Clean room classes 1-10 use unidirectional airflow with velocities ranging from 50-110 feet per minute and air changes from 300-650 per hour. Classes 1,000-100,000 use mixed airflow with velocities between 10-90 feet per minute and air changes of 10-250 per hour. Unidirectional airflow is defined as having an average velocity of 90 feet per minute plus or minus 20% and is used for classes 100 and below due to its effectiveness in particle removal through higher velocities.

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CIVIL
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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www.PDHcenter.com PDH Course M143 www.PDHonline.

org

Clean room Airflow Type Av. Airflow Velocity, Air changes/hr


Class fpm

1 Unidirectional 70-100 350-650

10 Unidirectional 60-110 300-600

100 Unidirectional 50-90 300-480

1,000 Mixed 40-90 150-250

10,000 Mixed 25-40 60-120

100,000 Mixed 10-30 10-40

List the specific design features of unidirectional airflow design?


Unidirectional airflow pattern is a requirement for absolute cleanliness and is conventionally

applied to spaces demanding class 100 levels or below. The principle underlying cleanliness for

unidirectional airflow pattern is the air velocity. Higher air velocity is advantageous in particle

removal/settlement.

IES Standard RP CC 002-86 “Laminar Flow Clean Air Devices” defines the level of acceptance

for velocity, as “Average measured clean air velocity should be 90 FPM. All measured values

should fall within plus or minus 20% of the measured average.

The common approach in designing a unidirectional airflow clean room is to simply fix the filter

velocity at 90 fpm and then specify different ceiling coverage percentages for different

classification levels.

Why 90 FPM?
The definition of “Laminar Flow”, 90 FPM plus or minus 20% does not exist officially. As a

common industry practice, manufacturers and designers design the systems at this velocity. The

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