EN ISO 14644-1:2015

Cleanrooms and associated controlled environments - Part 1: Classification of air cleanliness by particle concentration (ISO 14644-1:2015)

ISO 14644-1:2015 specifies the classification of air cleanliness in terms of concentration of airborne particles in cleanrooms and clean zones; and separative devices as defined in ISO 14644‑7.
Only particle populations having cumulative distributions based on threshold (lower limit) particle sizes ranging from 0,1 µm to 5 µm are considered for classification purposes.
The use of light scattering (discrete) airborne particle counters (LSAPC) is the basis for determination of the concentration of airborne particles, equal to and greater than the specified sizes, at designated sampling locations.
ISO 14644-1:2015 does not provide for classification of particle populations that are outside the specified lower threshold particle-size range, 0,1 µm to 5 µm. Concentrations of ultrafine particles (particles smaller than 0,1 µm) will be addressed in a separate standard to specify air cleanliness by nano-scale particles. An M descriptor (see Annex C) may be used to quantify populations of macroparticles (particles larger than 5 µm).
ISO 14644-1:2015 cannot be used to characterize the physical, chemical, radiological, viable or other nature of airborne particles.

Reinräume und zugehörige Reinraumbereiche - Teil 1: Klassifizierung der Luftreinheit anhand der Partikelkonzentration (ISO 14644-1:2015)

Dieser Teil der ISO 14644 enthält die Klassifizierung der Luftreinheit in Reinräumen und zugehörigen Rein¬raumbereichen sowie von SD-Modulen (en: separative device, SD) nach ISO 14644 7 anhand der Konzentration luftgetragener Partikel.
Für Klassifizierungszwecke werden nur Partikelgruppen in Betracht gezogen, deren Summenhäufigkeits-verteilung auf dem Schwellenwert der Partikelgröße (untere (Nachweis-)Grenze) beruht, der von 0,1 µm bis 5 µm reicht.
Die Anwendung von Streulicht-Einzelpartikelzählern (LSAPC, en. light scattering (discrete) airborne particle counter) ist die Grundlage für die Bestimmung der Konzentration luftgetragener Partikel gleich und größer dem festgelegten Größenbereich an gekennzeichneten Probenahmeorten.
Dieser Teil der ISO 14644 trifft nicht auf die Klassifizierung von Partikelgruppen zu, die außerhalb des fest-gelegten unteren Schwellenwerts (Nachweisgrenze) der Partikelgröße im Bereich zwischen 0,1 µm und 5 µm liegen. Konzentrationen von ultrafeinen Partikeln (nanoskalige Partikel kleiner als 0,1 µm) werden in einem anderen Teil der Normenreihe behandelt, der die Luftreinheit anhand der Partikelkonzentration luftgetragener Nano¬partikel festlegt, während ein M-Deskriptor (siehe Anhang C) zur Quantifizierung von Makropartikelgruppen (Partikel größer als 5 µm) angewendet werden darf.
Dieser Teil der ISO 14644 eignet sich nicht zur Charakterisierung der physikalischen, chemischen, radiologischen sowie der lebensfähigen (aktiven) oder der anderen Arten von luftgetragenen Partikeln.

Salles propres et environnements maîtrisés apparentés - Partie 1: Classification de la propreté particulaire de l'air (ISO 14644-1:2015)

ISO 14644-1:2015 spécifie la classification de la propreté de l'air des salles propres, des zones propres et des dispositifs séparatifs tels que définis dans l'ISO 14644‑7 en termes de concentration des particules en suspension dans l'air.
Seules sont prises en compte les populations de particules présentant une distribution granulométrique cumulée dont le seuil inférieur se situe dans l'étendue de 0,1 µm à 5 µm.
La méthode de référence pour déterminer la concentration de particules dans l'air d'une taille supérieure ou égale aux tailles spécifiées aux points de prélèvement désignés est l'utilisation de compteurs utilisant les propriétés de diffusion de la lumière (light scattering airborne particle counters - LSAPC).
La présente partie de l'ISO 14644 ne donne pas de classification pour des populations de particules dont le seuil inférieur se situe en dehors de l'étendue granulométrique de référence de 0,1 µm à 5 µm. Les concentrations de particules ultrafines (plus petites que 0,1 µm) seront traitées dans une norme séparée laquelle spécifiera la propreté particulaire de l'air à l'échelle nanométrique. Un descripteur M (voir l'Annexe C) pouvant être utilisé pour quantifier les populations de macroparticules (particules plus grandes que 5 µm).
ISO 14644-1:2015 ne peut pas être utilisée pour caractériser la nature physique, chimique, radiologique ou viable des particules en suspension dans l'air.

Čiste sobe in podobna nadzorovana okolja - 1. del: Klasifikacija čistosti zraka na osnovi koncentracije delcev (ISO 14644-1:2015)

Ta del evropskega standarda določa klasifikacijo čistosti na osnovi koncentracije delcev v čistih sobah in prostorih z nadzorom čistega zraka v treh možnih stanjih glede na količino delcev, prisotnih v zraku.

General Information

• Status: Published
• Publication Date: 22-Dec-2015
• ICS: 13.040.35 - Cleanrooms and associated controlled environments
• Technical Committee: CEN/TC 243 - Cleanroom technology
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Due Date: 11-Sep-2012
• Ref Project: SIST EN ISO 14644-1:2016 - Cleanrooms and associated controlled environments - Part 1: Classification of air cleanliness by particle concentration (ISO 14644-1:2015)

RELATIONS

• Replaces: EN ISO 14644-1:1999 - Cleanrooms and associated controlled environments - Part 1: Classification of air cleanliness (ISO 14644-1:1999)
• Effective Date: 30-Dec-2015

Standards Content (sample)

SLOVENSKI STANDARD
SIST EN ISO 14644-1:2016
01-marec-2016
1DGRPHãþD
SIST EN ISO 14644-1:2000

ýLVWHVREHLQSRGREQDQDG]RURYDQDRNROMDGHO.ODVLILNDFLMDþLVWRVWL]UDNDQD

RVQRYLNRQFHQWUDFLMHGHOFHY,62

Cleanrooms and associated controlled environments - Part 1: Classification of air

cleanliness by particle concentration (ISO 14644-1:2015)

Reinräume und zugehörige Reinraumbereiche - Teil 1: Klassifizierung der Luftreinheit

anhand der Partikelkonzentration (ISO 14644-1:2015)

Salles propres et environnements maîtrisés apparentés - Partie 1: Classification de la

propreté particulaire de l'air (ISO 14644-1:2015)
Ta slovenski standard je istoveten z: EN ISO 14644-1:2015
ICS:
13.040.35 Brezprašni prostori in Cleanrooms and associated
povezana nadzorovana controlled environments
okolja
SIST EN ISO 14644-1:2016 en

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

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SIST EN ISO 14644-1:2016
EN ISO 14644-1
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2015
EUROPÄISCHE NORM
ICS 13.040.35 Supersedes EN ISO 14644-1:1999
English Version
Cleanrooms and associated controlled environments - Part
1: Classification of air cleanliness by particle concentration
(ISO 14644-1:2015)

Salles propres et environnements maîtrisés apparentés Reinräume und zugehörige Reinraumbereiche - Teil 1:

- Partie 1: Classification de la propreté particulaire de Klassifizierung der Luftreinheit anhand der

l'air (ISO 14644-1:2015) Partikelkonzentration (ISO 14644-1:2015)
This European Standard was approved by CEN on 27 November 2015.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, 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: Avenue Marnix 17, B-1000 Brussels

© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14644-1:2015 E

worldwide for CEN national Members.
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EN ISO 14644-1:2015 (E)
Contents Page

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

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SIST EN ISO 14644-1:2016
EN ISO 14644-1:2015 (E)
European foreword

This document (EN ISO 14644-1:2015) 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 June 2016, and conflicting national standards shall be

withdrawn at the latest by June 2016.

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

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.
This document supersedes EN ISO 14644-1:1999.

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, Former Yugoslav Republic of Macedonia,

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

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 14644-1:2015 has been approved by CEN as EN ISO 14644-1:2015 without any

modification.
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SIST EN ISO 14644-1:2016
INTERNATIONAL ISO
STANDARD 14644-1
Second edition
2015-12-15
Cleanrooms and associated controlled
environments —
Part 1:
Classification of air cleanliness by
particle concentration
Salles propres et environnements maîtrisés apparentés —
Partie 1: Classification de la propreté particulaire de l’air
Reference number
ISO 14644-1:2015(E)
ISO 2015
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SIST EN ISO 14644-1:2016
ISO 14644-1:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2015 – All rights reserved
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SIST EN ISO 14644-1:2016
ISO 14644-1:2015(E)
Contents Page

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

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

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

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

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

3.1 General ........................................................................................................................................................................................................... 1

3.2 Airborne particles ................................................................................................................................................................................ 2

3.3 Occupancy states ................................................................................................................................................................................... 3

3.4 Testing instrumentation (see Annex F) ............................................................................................................................. 3

3.5 Instrument specifications .............................................................................................................................................................. 4

4 Classification ............................................................................................................................................................................................................ 4

4.1 Occupancy state(s) .............................................................................................................................................................................. 4

4.2 Particle size(s) ......................................................................................................................................................................................... 4

4.3 ISO Class number .................................................................................................................................................................................. 4

4.4 Designation ................................................................................................................................................................................................ 5

4.5 Intermediate decimal cleanliness classes and particle size thresholds ................................................. 5

5 Demonstration of compliance ................................................................................................................................................................ 6

5.1 Principle ........................................................................................................................................................................................................ 6

5.2 Testing ............................................................................................................................................................................................................ 6

5.3 Airborne particle concentration evaluation .................................................................................................................. 6

5.4 Test report ................................................................................................................................................................................................... 6

Annex A (normative) Reference method for classification of air cleanliness by

particle concentration .................................................................................................................................................................................... 8

Annex B (informative) Examples of classification calculations .............................................................................................13

Annex C (informative) Counting and sizing of airborne macroparticles .....................................................................22

Annex D (informative) Sequential sampling procedure ................................................................................................................27

Annex E (informative) Specification of intermediate decimal cleanliness classes and

particle size thresholds ..............................................................................................................................................................................34

Annex F (informative) Test instruments ........................................................................................................................................................36

Bibliography .............................................................................................................................................................................................................................37

© ISO 2015 – All rights reserved iii
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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 on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 209, Cleanrooms and associated controlled

environments.

This second edition cancels and replaces the first edition (ISO 14644-1:1999), which has been

technically revised throughout.

ISO 14644 consists of the following parts, under the general title Cleanrooms and associated controlled

environments:
— Part 1: Classification of air cleanliness by particle concentration

— Part 2: Monitoring to provide evidence of cleanroom performance related to air cleanliness by particle

concentration
— Part 3: Test methods
— Part 4: Design, construction and start-up
— Part 5: Operations

— Part 7: Separative devices (clean air hoods, gloveboxes, isolators and mini-environments)

— Part 8: Classification of air cleanliness by chemical concentration (ACC)
— Part 9: Classification of surface cleanliness by particle concentration
— Part 10: Classification of surface cleanliness by chemical concentration

Attention is also drawn to ISO 14698, Cleanrooms and associated controlled environments —

Biocontamination control:
— Part 1: General principles and methods
— Part 2: Evaluation and interpretation of biocontamination data
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Introduction

Cleanrooms and associated controlled environments provide for the control of contamination of air

and, if appropriate, surfaces, to levels appropriate for accomplishing contamination-sensitive activities.

Contamination control can be beneficial for protection of product or process integrity in applications in

industries such as aerospace, microelectronics, pharmaceuticals, medical devices, healthcare and food.

This part of ISO 14644 specifies classes of air cleanliness in terms of the number of particles expressed

as a concentration in air volume. It also specifies the standard method of testing to determine

cleanliness class, including selection of sampling locations.

This edition is the result of a response to an ISO Systematic Review and includes changes in response to

user and expert feedback validated by international enquiry. The title has been revised to “Classification

of air cleanliness by particle concentration” to be consistent with other parts of ISO 14644. The nine

ISO cleanliness classes are retained with minor revisions. Table 1 defines the particle concentration at

various particle sizes for the nine integer classes. Table E.1 defines the maximum particle concentration

at various particle sizes for intermediate classes. The use of these tables ensures better definition

of the appropriate particle-size ranges for the different classes. This part of ISO 14644 retains the

macroparticle descriptor concept; however, consideration of nano-scale particles (formerly defined as

ultrafine particles) will be addressed in a separate standard.

The most significant change is the adoption of a more consistent statistical approach to the selection and

the number of sampling locations; and the evaluation of the data collected. The statistical model is based

on adaptation of the hypergeometric sampling model technique, where samples are drawn randomly

without replacement from a finite population. The new approach allows each location to be treated

independently with at least a 95 % level of confidence that at least 90 % of the cleanroom or clean zone

areas will comply with the maximum particle concentration limit for the target class of air cleanliness.

No assumptions are made regarding the distribution of the actual particle counts over the area of the

cleanroom or clean zone; while in ISO 14644-1:1999 an underlying assumption was that the particle

counts follow the same normal distribution across the room, this assumption has now been discarded

to allow the sampling to be used in rooms where the particle counts vary in a more complex manner. In

the process of revision it has been recognized that the 95 % UCL was neither appropriate nor was applied

consistently in ISO 14644-1:1999. The minimum number of sampling locations required has been changed,

compared with ISO 14644-1:1999. A reference table, Table A.1, is provided to define the minimum number

of sampling locations required based on a practical adaptation of the sampling model technique. An

assumption is made that the area immediately surrounding each sampling location has a homogeneous

particle concentration. The cleanroom or clean zone area is divided up into a grid of sections of near equal

area, whose number is equal to the number of sampling locations derived from Table A.1. A sampling

location is placed within each grid section, so as to be representative of that grid section.

It is assumed for practical purposes that the locations are chosen representatively; a “representative”

location (see A.4.2) means that features such as cleanroom or clean zone layout, equipment disposition

and airflow systems should be considered when selecting sampling locations. Additional sampling

locations may be added to the minimum number of sampling locations.

Finally, the annexes have been reordered to improve the logic of this part of ISO 14644 and portions

of the content of certain annexes concerning testing and test instruments have been included from

ISO 14644-3:2005.

The revised version of this part of ISO 14644 addresses the ≥ 5 µm particle limits for ISO Class

5 in the sterile products annexes of the EU, PIC/S and WHO GMPs by way of an adaptation of the

macroparticle concept.

The revised version of this part of ISO 14644 now includes all matters related to classification of air

cleanliness by particle concentration. The revised version of ISO 14644-2:2015 now deals exclusively

with the monitoring of air cleanliness by particle concentration.

Cleanrooms may also be characterized by attributes in addition to the classification of air cleanliness by

particle concentration. Other attributes, such as air cleanliness in terms of chemical concentration, may

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be monitored and the attribute’s grade or level may be designated along with the classification of the ISO

Class of cleanliness. These additional attributes do not suffice alone to classify a cleanroom or clean zone.

vi © ISO 2015 – All rights reserved
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SIST EN ISO 14644-1:2016
INTERNATIONAL STANDARD ISO 14644-1:2015(E)
Cleanrooms and associated controlled environments —
Part 1:
Classification of air cleanliness by particle concentration
1 Scope

This part of ISO 14644 specifies the classification of air cleanliness in terms of concentration of airborne

particles in cleanrooms and clean zones; and separative devices as defined in ISO 14644-7.

Only particle populations having cumulative distributions based on threshold (lower limit) particle

sizes ranging from 0,1 µm to 5 µm are considered for classification purposes.

The use of light scattering (discrete) airborne particle counters (LSAPC) is the basis for determination

of the concentration of airborne particles, equal to and greater than the specified sizes, at designated

sampling locations.

This part of ISO 14644 does not provide for classification of particle populations that are outside the

specified lower threshold particle-size range, 0,1 µm to 5 µm. Concentrations of ultrafine particles

(particles smaller than 0,1 µm) will be addressed in a separate standard to specify air cleanliness

by nano-scale particles. An M descriptor (see Annex C) may be used to quantify populations of

macroparticles (particles larger than 5 µm).

This part of ISO 14644 cannot be used to characterize the physical, chemical, radiological, viable or

other nature of airborne particles.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

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

ISO 14644-2:2015, Cleanrooms and associated controlled environments — Part 2: Monitoring to provide

evidence of cleanroom performance related to air cleanliness by particle concentration

ISO 14644-7, Cleanrooms and associated controlled environments — Part 7: Separative devices (clean air

hoods, gloveboxes, isolators and mini-environments)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 General
3.1.1
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.
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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.
3.1.2
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 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.
3.1.3
installation

cleanroom or one or more clean zones, together with all associated structures, air-treatment systems,

services and utilities
3.1.4
classification

method of assessing level of cleanliness against a specification for a cleanroom or clean zone

Note 1 to entry: Levels should be expressed in terms of an ISO Class, which represents maximum allowable

concentrations of particles in a unit volume of air.
3.2 Airborne particles
3.2.1
particle
minute piece of matter with defined physical boundaries
3.2.2
particle size

diameter of a sphere that produces a response, by a given particle-sizing instrument, that is equivalent

to the response produced by the particle being measured

Note 1 to entry: For discrete-particle light-scattering instruments, the equivalent optical diameter is used.

3.2.3
particle concentration
number of individual particles per unit volume of air
3.2.4
particle size distribution
cumulative distribution of particle concentration as a function of particle size
3.2.5
macroparticle
particle with an equivalent diameter greater than 5 µm
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3.2.6
M descriptor

designation for measured or specified concentration of macroparticles per cubic metre of air, expressed

in terms of the equivalent diameter that is characteristic of the measurement method used

Note 1 to entry: The M descriptor can be regarded as an upper limit for the averages at sampling locations.

M descriptors cannot be used to define ISO Classes, but the M descriptor may be quoted independently or in

conjunction with ISO Classes.
3.2.7
unidirectional airflow

controlled airflow through the entire cross-section of a cleanroom or a clean zone with a steady velocity

and airstreams that are considered to be parallel
3.2.8
non-undirectional airflow

air distribution where the supply air entering the cleanroom or clean zone mixes with the internal air

by means of induction
3.3 Occupancy states
3.3.1
as-built

condition where the cleanroom or clean zone is complete with all services connected and functioning

but with no equipment, furniture, materials or personnel present
3.3.2
at-rest

condition where the cleanroom or clean zone is complete with equipment installed and operating in a

manner agreed upon, but with no personnel present
3.3.3
operational

agreed condition where the cleanroom or clean zone is functioning in the specified manner, with

equipment operating and with the specified number of personnel present
3.4 Testing instrumentation (see Annex F)
3.4.1
resolution

smallest change in a quantity being measured that causes a perceptible change in the corresponding

indication

Note 1 to entry: Resolution can depend on, for example, noise (internal or external) or friction. It may also depend

on the value of a quantity being measured.
[SOURCE: ISO/IEC Guide 99:2007, 4.14]
3.4.2
maximum permissible measurement error

extreme value of measurement error, with respect to a known reference quantity value, permitted by

specifications or regulations for a given measurement, measuring instrument, or measuring system

Note 1 to entry: Usually, the term “maximum permissible errors” or “limits of error” is used where there are two

extreme values.

Note 2 to entry: The term “tolerance” should not be used to designate “maximum permissible error”.

[SOURCE: ISO/IEC Guide 99:2007, 4.26]
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3.5 Instrument specifications
3.5.1
LSAPC
light scattering airborne particle counter
light scattering discrete airborne particle counter

instrument capable of counting and sizing single airborne particles and reporting size data in terms of

equivalent optical diameter
Note 1 to entry: The specifications for the LSAPC are given in ISO 21501-4:2007.
3.5.2
discrete-macroparticle counter
instrument capable of counting and sizing single airborne macroparticles
Note 1 to entry: See Table F.1 for specifications.
3.5.3
time-of-flight particle sizing apparatus

discrete-particle counting and sizing apparatus that defines the aerodynamic diameter of particles by

measuring the time for a particle to accommodate to a change in air velocity

Note 1 to entry: This is usually done by measuring the particle transit time optically after a fluid stream

velocity change.
Note 2 to entry: See Table F.2 for specifications.
4 Classification
4.1 Occupancy state(s)

The air cleanliness class by particle concentration of air in a cleanroom or clean zone shall be defined in

one or more of three occupancy states, viz. “as-built,” “at-rest” or “operational” (see 3.3).

4.2 Particle size(s)

One, or more than one, threshold (lower limit) particle sizes situated within the range from ≥0,1 µm to

≥5 µm are to be used to determine air cleanliness particle concentration for classification.

4.3 ISO Class number

Air cleanliness class by particle concentration shall be designated by an ISO Class number, N. The maximum

permitted concentration of particles for each considered particle size is determined from Table 1.

Particle number concentrations for different threshold sizes in Table 1 do not reflect actual

...