Cleanrooms and associated controlled environments - Part 17: Particle deposition rate applications (ISO 14644-17:2021)

This document gives direction on the interpretation and application of the results of the measurement
of particle deposition rate on one or more vulnerable surfaces in a cleanroom as part of a contamination
control programme. It provides some instructions on how to influence the particle deposition rate and
reduce the risk of particle contamination on vulnerable surfaces.
This document gives information on how a cleanroom user can use the particle deposition rate
measurements to determine limits that can be set for macroparticles on vulnerable surfaces. It also
gives a risk assessment method by which an acceptable risk of deposition of particles onto vulnerable
surfaces in a cleanroom can be established and, when this is not achieved, methods that can be used to
reduce the particle deposition rate.
An alternative to the particle deposition rate is the particle obscuration rate which determines the rate
of increase of coverage of particles onto an area of surface over time. The particle obscuration rate can
be used in an analogous way to the particle deposition rate and the required particle obscuration rate
for a specified surface can be calculated and the risk from deposited particles reduced.
This document does not:
— provide a method to classify a cleanroom with respect to particle deposition rate or particle
obscuration rate;
— directly consider the deposition of microbe-carrying particles, although they can be treated as
particles;
— give any consideration to surface deposition by contact as, for example, when personnel touch a
product and contamination is transferred.

Reinräume und zugehörige Reinraumbereiche - Teil 17: Anwendungen zur Partikelabscheidungsrate (ISO 14644-17:2021)

Dieses Dokument enthält Anweisungen für die Auswertung und Anwendung der Messergebnisse der Partikelablagerungsrate auf einer oder mehreren empfindlichen Oberflächen in einem Reinraum im Rahmen eines Programms zur Kontaminationskontrolle. Es umfasst ferner Anleitungen, wie die Partikelablagerungs-rate beeinflusst und die Gefahr einer partikulären Kontamination auf empfindlichen Oberflächen verringert werden kann.
Dieses Dokument beschreibt, wie Nutzer eines Reinraums mit Hilfe der Messungen der Partikelablagerungs-rate Grenzwerte festlegen können, die für Makropartikel auf empfindlichen Oberflächen gelten. Es umfasst ferner ein Verfahren zur Risikobewertung, mit dem ein annehmbares Risiko der Partikelablagerung auf empfindlichen Oberflächen in einem Reinraum ermittelt werden kann und, wenn dieses nicht erreicht wird, Verfahren, mit denen die Partikelablagerungsrate reduziert werden kann.
Eine Alternative zur Partikelablagerungsrate ist die partikuläre Trübungsrate, mit der die Anstiegsrate der Partikelansammlung auf einer bestimmten Fläche während einer bestimmten Zeit ermittelt werden kann. Die partikuläre Trübungsrate kann analog zur Partikelablagerungsrate angewandt werden, die erforderliche partikuläre Trübungsrate für eine bestimmte Oberfläche kann berechnet und das Risiko durch abgelagerte Partikel verringert werden.
Folgendes leistet dieses Dokument nicht:
- Bestimmung eines Verfahrens zur Klassifizierung eines Reinraums in Bezug auf die Partikelablagerungs-rate oder partikuläre Trübungsrate;
- direkte Betrachtung der Ablagerung mikrobentragender Partikel (MCP, en: microbe-carrying particles), wenngleich diese als Partikel behandelt werden können;
- Betrachtung der Ablagerung auf Oberflächen durch Kontakt, zum Beispiel wenn Mitarbeiter ein Produkt berühren und eine Kontamination auf diese Weise übertragen wird.

Salles propres et environnements maîtrisés apparentés - Partie 17: Applications de taux de dépôt de particules (ISO 14644-17:2021)

Čiste sobe in podobna nadzorovana okolja - 17. del: Aplikacije glede hitrosti usedanja delcev (ISO 14644-17:2021)

General Information

Status
Published
Public Enquiry End Date
29-Feb-2020
Publication Date
08-Mar-2021
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
04-Mar-2021
Due Date
09-May-2021
Completion Date
09-Mar-2021

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SLOVENSKI STANDARD
SIST EN ISO 14644-17:2021
01-april-2021
Čiste sobe in podobna nadzorovana okolja - 17. del: Aplikacije glede hitrosti
usedanja delcev (ISO 14644-17:2021)

Cleanrooms and associated controlled environments - Part 17: Particle deposition rate

applications (ISO 14644-17:2021)
Reinräume und zugehörige Reinraumbereiche - Teil 17: Anwendungen zur
Partikelabscheidungsrate (ISO 14644-17:2021)

Salles propres et environnements maîtrisés apparentés - Partie 17: Applications de taux

de dépôt de particules (ISO 14644-17:2021)
Ta slovenski standard je istoveten z: EN ISO 14644-17:2021
ICS:
13.040.35 Brezprašni prostori in Cleanrooms and associated
povezana nadzorovana controlled environments
okolja
SIST EN ISO 14644-17:2021 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 14644-17:2021
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SIST EN ISO 14644-17:2021
EN ISO 14644-17
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2021
EUROPÄISCHE NORM
ICS 13.040.35
English Version
Cleanrooms and associated controlled environments - Part
17: Particle deposition rate applications (ISO 14644-
17:2021)

Salles propres et environnements maîtrisés apparentés Reinräume und zugehörige Reinraumbereiche - Teil

- Partie 17: Applications de taux de dépôt de particules 17: Anwendungen zur Partikelabscheidungsrate (ISO

(ISO 14644-17:2021) 14644-17:2021)
This European Standard was approved by CEN on 6 January 2021.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14644-17:2021 E

worldwide for CEN national Members.
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SIST EN ISO 14644-17:2021
EN ISO 14644-17:2021 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 14644-17:2021
EN ISO 14644-17:2021 (E)
European foreword

This document (EN ISO 14644-17:2021) has been prepared by Technical Committee ISO/TC 209

"Cleanrooms and associated controlled environments" in collaboration with Technical Committee

CEN/TC 243 “Cleanroom technology” the secretariat of which is held by BSI.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by August 2021, and conflicting national standards shall

be withdrawn at the latest by August 2021.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 14644-17:2021 has been approved by CEN as EN ISO 14644-17:2021 without any

modification.
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SIST EN ISO 14644-17:2021
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SIST EN ISO 14644-17:2021
INTERNATIONAL ISO
STANDARD 14644-17
First edition
2021-02
Cleanrooms and associated controlled
environments —
Part 17:
Particle deposition rate applications
Salles propres et environnements maîtrisés apparentés —
Partie 17: Applications de taux de dépôt de particules
Reference number
ISO 14644-17:2021(E)
ISO 2021
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols .......................................................................................................................................................................................................................... 3

5 Particle deposition rate methodology ........................................................................................................................................... 4

5.1 General ........................................................................................................................................................................................................... 4

5.2 Establishing the particle deposition rate required for control of particle deposition

on vulnerable surfaces ..................................................................................................................................................................... 4

5.3 Particle deposition rate for demonstrating control of particle contamination ............................... 5

6 Measurement of particle deposition rate ................................................................................................................................... 5

7 Particle deposition rate level ................................................................................................................................................................... 6

8 Documentation ....................................................................................................................................................................................................... 7

Annex A (informative) Measurement of particle deposition rate .......................................................................................... 8

Annex B (informative) Examples of particle deposition rate measurements .........................................................12

Annex C (informative) Measurement of the particle obscuration ......................................................................................16

Annex D (informative) Relationship between particle deposition rate and airborne

concentration of particles ........................................................................................................................................................................19

Annex E (informative) Assessment and control of particle deposition .........................................................................20

Bibliography .............................................................................................................................................................................................................................25

© ISO 2021 – All rights reserved iii
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 209, Cleanrooms and associated controlled

environments, in collaboration with the European Committee for Standardization (CEN) Technical

Committee CEN/TC 243, Cleanroom technology, in accordance with the Agreement on technical

cooperation between ISO and CEN (Vienna Agreement).

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
A list of all parts in the ISO 14644 series can be found on the ISO website.
iv © ISO 2021 – All rights reserved
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)
Introduction

Cleanrooms and associated controlled environments are used to control contamination to levels

appropriate for accomplishing contamination-sensitive activities. Products and processes that benefit

from the control of contamination include those in industries such as aerospace, microelectronics,

optics, nuclear, food, healthcare, pharmaceuticals, and medical devices.

ISO 14644-1:2015 considers airborne particles in cleanrooms and classifies cleanroom cleanliness

by maximum permitted concentrations, and both ISO 14644-9:2012 and IEST -STD -CC1246E: 2013

consider the concentration of surface particles. This document considers the rate of particle deposition

[5]

onto cleanroom surfaces and is based on VCCN Guideline 9 . The particle deposition rate is important,

as the probability of contamination by airborne particles onto contamination sensitive, vulnerable

surfaces, such as manufactured products, is directly related to the particle deposition rate.

ISO 14644-3:2019 gives an overview of methods for the determination of deposition of particles, larger

or equal to 0,1 µm. In this document, the focus is on the rate that macroparticles larger than 5 µm

deposit on surfaces, and the application of this information to controlling contamination in cleanrooms.

Various sizes of particles are generated in cleanrooms by personnel, machinery, tools, and processes,

and distributed by air moving about the cleanroom. According to ISO 14644-1, cleanrooms and

controlled environments with a particle class of the ISO 5 series, or cleaner, contain zero or very low

concentrations of airborne particles larger than 5 µm. However, in operating cleanrooms, many more

particles in the size range of 5 µm to 500 µm, and greater, are found on surfaces than suggested by the

classification limits of the size of particles given in ISO 14644-1. The main reason for this is that the

largest particles in the range of sizes of macroparticles are not counted by particle counters because

of deposition losses in sampling tubes, and at the entry to and within particle counters. Also, for the

same reason, only a proportion of the smaller particles in the range of sizes is measured. In many cases,

large particles cause contamination problems and their presence and potential for deposition onto

contamination sensitive, vulnerable surfaces is best determined by measuring the particle deposition

rate onto surfaces.

Particles smaller than 5 µm are most likely to be removed from the cleanroom air by the ventilation

system but, for particles above 10 µm, more than 50 % is removed from the air by surface deposition.

Above 40 µm, more than 90 % is deposited (see Reference [6]). The dominant deposition mechanism of

this size of particles has been shown to be gravitational but air turbulence and electrostatic attraction

can also cause deposition (see Reference [7]). These deposited particles can be re-dispersed by walking

and cleaning actions, but not by air velocities associated with the cleanroom air. It is important that

these particles are removed by cleaning.

The presence and redistribution of particles >5 µm in cleanrooms is mostly related to human or

mechanical activity. In a cleanroom "at rest", there is likely to be little activity and dispersion of

particles, and the concentration of particles larger than 5 µm is close to zero with no significant particle

deposition. Therefore, it is only in the "operational" occupancy state that the particle deposition rate

should be considered.

The particle deposition rate is an attribute of a cleanroom or clean zone that determines the likely rate

of deposition of airborne particles onto cleanroom surfaces, such as product or process area. Using a

risk assessment, the acceptable amount of contamination of a vulnerable surface can be defined, and

the particle deposition rate can then be obtained that ensures that this amount of contamination is not

exceeded.

Methods of measuring the particle deposition rate in a cleanroom or clean zone are given in this

document. These are used during the operation of the cleanroom to ensure that the required particle

deposition rate is obtained, and for monitoring the cleanroom and clean zones to demonstrate

continuous control of airborne contamination. Monitoring the particle deposition rate also enables

PDR peaks to be correlated with activities so as to detect sources of contamination, and indicate what

changes are required to working procedures to reduce the contamination risk.
© ISO 2021 – All rights reserved v
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)

The particle deposition rate is the rate of deposition of particles onto surfaces over time, and can be

calculated as the change of particle surface concentration per m during the time of exposure in hours

and can be expressed as Formula (1):
CC−
R = (1)
tt−
where

R is the deposition rate of particles equal to, or larger than D (µm) per m per hour;

C is the final particle surface concentration (number per m ) for particles equal to and larger

than D (µm);

C is the initial particle surface concentration (number per m ) for particles equal to and larger

than D (µm);
t is the final time of exposure (h);
t is the initial time of exposure (h).

If the particle deposition rate is determined on, or in close proximity to, a vulnerable surface, such as

product, then an estimate of the deposition of airborne particles onto the surface can be obtained by

applying Formula (2):
NR =⋅ta⋅ (2)
where
N number of deposited particles larger than or equal to particle size D (µm);
t is the time the surface is exposed to particle deposition (h);
a is the surface area exposed to airborne contamination (m ).

Some industries use cleanrooms to manufacture optical instruments and components, such as mirrors,

lenses, and solar panels used in aerospace. The quality of these products is related to the amount of

light absorbed or reflected by particles on the surface. Therefore, this document also considers particle

obscuration rate of test surfaces exposed in cleanrooms in Annex C. Using the particle deposition rate

of various particle sizes, the particle obscuration rate of airborne particles depositing onto a surface

and obscuring light can be calculated and used in a similar way to the particle deposition rate to reduce

the risk of surface contamination.
vi © ISO 2021 – All rights reserved
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SIST EN ISO 14644-17:2021
INTERNATIONAL STANDARD ISO 14644-17:2021(E)
Cleanrooms and associated controlled environments —
Part 17:
Particle deposition rate applications
1 Scope

This document gives direction on the interpretation and application of the results of the measurement

of particle deposition rate on one or more vulnerable surfaces in a cleanroom as part of a contamination

control programme. It provides some instructions on how to influence the particle deposition rate and

reduce the risk of particle contamination on vulnerable surfaces.

This document gives information on how a cleanroom user can use the particle deposition rate

measurements to determine limits that can be set for macroparticles on vulnerable surfaces. It also

gives a risk assessment method by which an acceptable risk of deposition of particles onto vulnerable

surfaces in a cleanroom can be established and, when this is not achieved, methods that can be used to

reduce the particle deposition rate.

An alternative to the particle deposition rate is the particle obscuration rate which determines the rate

of increase of coverage of particles onto an area of surface over time. The particle obscuration rate can

be used in an analogous way to the particle deposition rate and the required particle obscuration rate

for a specified surface can be calculated and the risk from deposited particles reduced.

This document does not:

— provide a method to classify a cleanroom with respect to particle deposition rate or particle

obscuration rate;

— directly consider the deposition of microbe-carrying particles, although they can be treated as

particles;

— give any consideration to surface deposition by contact as, for example, when personnel touch a

product and contamination is transferred.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 14644-3:2019, Cleanrooms and associated controlled environments — Part 3: Test methods

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
© ISO 2021 – All rights reserved 1
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)
3.1
cleanroom

room within which the number concentration of airborne particles is controlled and classified, and

which is designed, constructed and operated in a manner to control the introduction, generation and

retention of particles inside the room
Note 1 to entry: The class of airborne particle concentration is specified.

Note 2 to entry: Levels of other cleanliness attributes such as chemical, viable or nanoscale concentrations in the

air, and also surface cleanliness in terms of particle, nanoscale, chemical and viable concentrations might also be

specified and controlled.

Note 3 to entry: Other relevant physical parameters might also be controlled as required, e.g. temperature,

humidity, pressure, vibration and electrostatic.
[SOURCE: ISO 14644-1:2015, 3.1.1]
3.2
clean zone

defined space within which the number concentration of airborne particles is controlled and classified,

and which is constructed and operated in a manner to control the introduction, generation, and

retention of contaminants inside the space
Note 1 to entry: The class of airborne particle concentration is specified.

Note 2 to entry: Levels of other cleanliness attributes such as chemical, viable or nanoscale concentrations in the

air, and also surface cleanliness in terms of particle, nanoscale, chemical and viable concentrations might also be

specified and controlled.

Note 3 to entry: A clean zone(s) can be a defined space within a cleanroom (3.1) or might be achieved by a

separative device. Such a device can be located inside or outside a cleanroom.

Note 4 to entry: Other relevant physical parameters might also be controlled as required, e.g. temperature,

humidity, pressure, vibration and electrostatic.
[SOURCE: ISO 14644-1:2015, 3.1.2]
3.3
critical particle size

smallest particle size (3.7) that negatively impacts on product or process quality

3.4
critical location
location where a vulnerable surface (3.12) is exposed to particle contamination
3.5
operational

agreed condition where the cleanroom (3.1) or clean zone (3.2) is functioning in the specified manner,

with equipment operating and with the specified number of personnel present
[SOURCE: ISO 14644-1:2015, 3.3.3]
3.6
particle
minute piece of matter with defined physical boundaries
[SOURCE: ISO 14644-1:2015, 3.2.1]
2 © ISO 2021 – All rights reserved
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)
3.7
particle size

diameter of a sphere or the diameter of a sphere (circle) that encompasses a non-spherical particle, or

an equivalent diameter

Note 1 to entry: The definition should be stated in relation to the measurement method.

Note 2 to entry: In ISO 14644-1, light scattering based detection is used. Other measurement methods yield

different size definitions (see A.1).
3.8
particle deposition rate
PDR

number of particles depositing onto a known surface area during a known time of exposure

Note 1 to entry: It is expressed in number per m per hour.
3.9
particle deposition rate level
PDRL
level of particle deposition rates (3.8) for a range of particle sizes (3.7)
3.10
particle obscuration rate
POR
rate of change of particle area coverage of a surface during time of exposure
3.11
test surface

surface of specific area and known surface cleanliness used to collect particles that deposit from the air

in a specified time

Note 1 to entry: A test surface is used in this document to determine the particle deposition rate (3.8).

Note 2 to entry: A test surface can be a witness plate or an integral part of a measuring instrument.

3.12
vulnerable surface

surface whose functionality diminishes when particles larger than the critical size are present

3.13
witness plate

clean flat plate of a specified surface area used to collect particles that deposit from the air in a

specified time

Note 1 to entry: A witness plate is exposed adjacent to a vulnerable surface (3.12) to obtain the particle deposition

rate that occurs at that location.

Note 2 to entry: A witness plate is not normally part of a measuring instrument and, after exposure, the witness

plate is taken to a measuring instrument for the counting and sizing of the particles deposited.

4 Symbols
a product area in m
A area of the silhouette of the observed particles (mm )
C particle concentration in number of particles ≥D µm per m
D particle size in micrometres
© ISO 2021 – All rights reserved 3
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)
F particle obscuration rate
L particle deposition rate level
N number of particles ≥D µm deposited onto a surface
η efficiency of detection method
2 -2
O particle obscuration factor (in mm ·m )
R particle deposition rate in number of particles ≥D µm per m ·h
t time of exposure
5 Particle deposition rate methodology
5.1 General

Particle deposition rate data obtained in a cleanroom can be used to establish the probability of

airborne particles depositing onto a vulnerable surface during exposure and provide a methodology

that supports the required quality of a cleanroom during operation. The information in 5.2 and 5.3 gives

a method that can be used to establish the correct particle deposition rate cleanliness conditions in a

cleanroom and associated controlled environments. This information is used to demonstrate continued

control of these cleanliness conditions. ISO 14644-2 shall be considered as a guide for the development

and application of a monitoring plan.

5.2 Establishing the particle deposition rate required for control of particle deposition

on vulnerable surfaces

Establishing control of macroparticles in the controlled environment through use of the particle

deposition rate is required when a new facility is designed, or when cleanliness requirements are

changed in existing facilities. An assessment shall be made of the product attributes and the process

activities performed in the cleanroom. Based on this assessment, the required degree of control of

particle contamination shall be established using the following steps.

1) The surfaces in the cleanroom or associated controlled environments that are vulnerable to particle

deposition shall be identified. This can be done by considering the manufacturing carried out in

the cleanroom, the status of the technical installations, production equipment, and operational

procedures.

2) The smallest particle size that impacts on product or production quality on each vulnerable surface

(critical particle size) shall be determined.

NOTE 1 Differences in particle type (metallic vs non-metallic, transparent vs opaque, microbial vs non-

microbial) can lead to a particle-specific approach.

3) The maximum number of particles of the critical size that contaminates each vulnerable surface

considered shall be determined.

4) Knowing the maximum number of particles of a critical size that is acceptable on each surface, the

particle deposition rate or particle deposition rate level (see Table 1) at the critical particle size

shall be determined.

5) The critical surface with the tightest requirements on particle deposition rate and particle

deposition rate level will determine the particle deposition rate and particle deposition rate level

for the critical area.

6) After the maximum particle deposition rate or particle deposition rate level requirements are

defined for the critical area, the measurement method shall be chosen and put into operation. The

4 © ISO 2021 – All rights reserved
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SIST EN ISO 14644-17:2021
ISO 14644-17:2021(E)

method can be selected based on sensitivity, required measurement frequency, and other factors

such as ease of use. ISO 14644-3 can be consulted for information on measurement methods.

NOTE 2 Examples of the method
...

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