EN ISO 14644-1:2015

SLOVENSKI STANDARD
01-marec-2016
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SIST EN ISO 14644-1:2000
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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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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.

Contents Page
European foreword . 3

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.
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
ISO 14644-1:2015(E)
© 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. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved

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 14644-1:2015(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 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
iv © ISO 2015 – All rights reserved

ISO 14644-1:2015(E)
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
ISO 14644-1:2015(E)
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

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.
ISO 14644-1:2015(E)
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
2 © ISO 2015 – All rights reserved

ISO 14644-1:2015(E)
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]
ISO 14644-1:2015(E)
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 particle size
and number distribution in the air and serve as criteria for classification only. Examples of classification
calculations are included in Annex B.
4 © ISO 2015 – All rights reserved

ISO 14644-1:2015(E)
Table 1 — ISO Classes of air cleanliness by particle concentration
ISO Class number Maximum allowable concentrations (particles/m ) for particles equal to and greater
a
(N) than the considered sizes, shown below
0,1 µm 0,2 µm 0,3 µm 0,5 µm 1 µm 5 µm
b d d d d e
1 10
b b d d e
2 100 24 10
b d e
3 1 000 237 102 35
b e
4 10 000 2 370 1 020 352 83
d, e, f
5 100 000 23 700 10 200 3 520 832
6 1 000 000 237 000 102 000 35 200 8 320 293
c c c
7 352 000 83 200 2 930
c c c
8 3 520 000 832 000 29 300
g c c c
9 35 200 000 8 320 000 293 000
a
All concentrations in the table are cumulative, e.g. for ISO Class 5, the 10 200 particles shown at 0,3 µm include all
particles equal to and greater than this size.
b
These concentrations will lead to large air sample volumes for classification. Sequential sampling procedure may be
applied; see Annex D.
c
Concentration limits are not applicable in this region of the table due to very high particle concentration.
d
Sampling and statistical limitations for particles in low concentrations make classification inappropriate.
e
Sample collection limitations for both particles in low concentrations and sizes greater than 1 μm make classification
at this particle size inappropriate, due to potential particle losses in the sampling system.
f
In order to specify this particle size in association with ISO Class 5, the macroparticle descriptor M may be adapted and
used in conjunction with at least one other particle size. (See C.7.)
g
This class is only applicable for the in-operation state.
4.4 Designation
The designation of airborne particle concentration for cleanrooms and clean zones shall include
a) the ISO Class number, expressed as “ISO Class N”,
b) the occupancy state to which the classification applies, and
c) the considered particle size(s).
If measurements are to be made at more than one considered particle size, each larger particle diameter
(e.g. D2) shall be at least 1,5 times the next smaller particle diameter (e.g. D1), i.e. D2 ≥ 1,5 × D1.
EXAMPLE ISO Class number; occupancy state; considered particle size(s)
ISO Class 4; at rest; 0,2 µm, 0,5 µm
4.5 Intermediate decimal cleanliness classes and particle size thresholds
Where intermediate classes, or intermediate particle size thresholds for integer and intermediate
classes are required, refer to informative Annex E.
ISO 14644-1:2015(E)
5 Demonstration of compliance
5.1 Principle
Compliance with air cleanliness (ISO Class) requirements specified by the customer is verified
by performing specified testing procedures and by providing documentation of the results and
conditions of testing.
At-rest or operational classification may be performed periodically based upon risk assessment of the
application, typically on an annual basis.
For monitoring cleanrooms, clean zones and separative devices, ISO 14644-2:2015 shall be used.
NOTE Where the installation is equipped with instrumentation for continuous or frequent monitoring
of air cleanliness by particle concentration and other parameters of performance as applicable, the time
intervals between classification may be extended provided that the results of the monitoring remain within
the specified limits.
5.2 Testing
The reference test method for demonstrating compliance is given in Annex A (normative). Alternative
methods or instrumentation (or both), having at least comparable performance, may be specified. If no
alternative is specified or agreed upon, the reference method shall be used.
Tests performed to demonstrate compliance shall be conducted using instruments which are in
compliance with calibration requirements at the time of testing.
5.3 Airborne particle concentration evaluation
Upon completion of testing in accordance with Annex A, the concentration of particles (expressed as
number of particles per cubic metre) in a single sample volume at each sampling location shall not
exceed the concentration limit(s) given in Table 1 or Table E.1 for intermediate decimal classes for the
considered size(s). If multiple single sample volumes are taken at a sampling location, the concentrations
shall be averaged and the average concentration must not exceed the concentration limits given in
Table 1 or Table E 1. Intermediate particle sizes shall be derived from Formula (E.1).
Particle concentrations used for determination of compliance with ISO Classes shall be measured by
the same method for all considered particle sizes.
5.4 Test report
The results from testing each cleanroom or clean zone shall be recorded and submitted as a
comprehensive report, along with a statement of compliance or non-compliance with the specified
designation of air cleanliness class by particle concentration.
The test report shall include
a) the name and address of the testing organization, and the date on which the test was performed,
b) the number and year of publication of this part of ISO 14644, i.e. ISO 14644-1:2015,
c) a clear identification of the physical location of the cleanroom or clean zone tested (including
reference to adjacent areas if necessary), and specific designations for coordinates of all sampling
locations (a diagrammatic representation can be helpful),
d) the specified designation criteria for the cleanroom or clean zone, including the ISO Class number,
the relevant occupancy state(s), and the considered particle size(s),
e) details of the test method used, with any special conditions relating to the test, or departures from
the test method, and identification of the test instrument and its current calibration certificate, and
6 © ISO 2015 – All rights reserved

ISO 14644-1:2015(E)
f) the test results, including particle concentration data for all sampling locations.
If concentrations of macroparticles are quantified, as described in Annex C, the relevant information
should be included with the test report.
ISO 14644-1:2015(E)
Annex A
(normative)
Reference method for classification of air cleanliness by particle
concentration
A.1 Principle
A discrete-particle-counting instrument is used to determine the concentration of airborne particles,
equal to and greater than the specified sizes, at designated sampling locations.
A.2 Apparatus requirements
A.2.1 Particle-counting instrument
The instrument shall have a means of displaying or recording the count and size of discrete particles
in air with a size discrimination capability to detect the total particle concentration in the appropriate
particle size ranges for the class under consideration.
NOTE Light scattering (discrete) airborne particle counters (LSAPC) are commonly used for undertaking air
cleanliness classification.
A.2.2 Instrument calibration
The particle counter shall have a valid calibration certificate: the frequency and method of calibration
[1]
should be based upon current accepted practice as specified in ISO 21501-4.
NOTE Some particle counters cannot be calibrated to all of the required tests in ISO 21501-4. If this is the
case, record the decision to use the counter in the test report.
A.3 Preparation for particle count testing
Prior to testing, verify that all relevant aspects of the cleanroom or clean zone that contribute to its
integrity are complete and functioning in accordance with its performance specification.
Care should be taken when determining the sequence for performing supporting tests for cleanroom
performance. ISO 14644-3, Annex A provides a checklist.
A.4 Establishment of sampling locations
A.4.1 Deriving the number of sampling locations
Derive the minimum number of sampling locations, N , from Table A.1. Table A.1 provides the number
L
of sampling locations related to the area of each cleanroom or clean zone to be classified and provides
at least 95 % confidence that at least 90 % of the cleanroom or clean zone area does not exceed the
class limits.
8 © ISO 2015 – All rights reserved

ISO 14644-1:2015(E)
Table A.1 — Sampling locations related to cleanroom area
Area of cleanroom (m ) Minimum number of sampling
less than or equal to locations to be tested (N )
L
2 1
4 2
6 3
8 4
10 5
24 6
28 7
32 8
36 9
52 10
56 11
64 12
68 13
72 14
76 15
104 16
108 17
116 18
148 19
156 20
192 21
232 22
276 23
352 24
436 25
636 26
1 000 27
> 1 000 See Formula (A.1)
NOTE 1 If the considered area falls between two values in the table, the greater of the two
should be selected.
NOTE 2 In the case of unidirectional airflow, the area may be considered as the cross
section of the moving air perpendicular to the direction of the airflow. In all other cases the
area may be considered as the horizontal plan area of the cleanroom or clean zone.
A.4.2 Positioning the sampling locations
In order to position the sampling locations
a) use the minimum number of sampling locations N derived from Table A.1,
L
b) then divide the whole cleanroom or clean zone into N sections of equal area,
L
c) select within each section a sampling location considered to be representative of the characteristics
of the section, and
ISO 14644-1:2015(E)
d) at each location, position the particle counter probe in the plane of the work activity or another
specified point.
Additional sampling locations may be selected for locations considered critical. Their number and
positions shall also be agreed and specified.
Additional sections and associated sampling locations may be included to facilitate subdivision into
equal sections.
For non-unidirectional airflow cleanrooms or clean zones, locations may not be representative if they
are located directly beneath non-diffused supply air sources.
A.4.3 Sampling locations for large cleanrooms or clean zones
When the area of the cleanroom or clean zone is greater than 1 000 m , apply Formula (A.1) to determine
the minimum number of sampling locations required.
 
 
A


N =×27  (A.1)


L


1000
 
 
where
N is the minimum number of sampling locations to be evaluated, rounded up to the next whole
L
number;
A is the area of the cleanroom in m .
A.4.4 Establishment of single sample volume and sampling time per location
At each sampling location, sample a volume of air sufficient to detect a minimum of 20 particles
if the particle concentration for the largest selected particle size were at the class limit for the
designated ISO Class.
The single sample volume, V , per sampling location is determined by using Formula (A.2):
s
 
 



V = ×1000 (A.2)

s


C
 

 nm, 
where
Vs is the minimum single sample volume per location, expressed in litres (except see Annex D);
C is the class limit (number of particles per cubic metre) for the largest considered particle
n,m
size specified for the relevant class;
20 is the number of particles that could be counted if the particle concentration were at the
class limit.
The volume sampled at each location shall be at least 2 l, with a minimum sampling time of 1 min for
each sample at each location. Each single sample volume at each sampling location shall be the same.
When V is very large, the time required for sampling can be substantial. By using the optional
s
sequential sampling procedure (see Annex D), both the required sample volume and the time required
to obtain samples may be reduced.
A.5 Sampling procedure
A.5.1 Set up the particle counter (see A.2) in accordance with the manufacturer’s instructions including
performing a zero count check.
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ISO 14644-1:2015(E)
A.5.2 The sampling probe shall be positioned pointing into the airflow. If the direction of the airflow
being sampled is not controlled or predictable (e.g. non-unidirectional airflow), the inlet of the sampling
probe shall be directed vertically upward.
A.5.3 Ensure normal conditions for the selected occupancy state are established before sampling.
A.5.4 Sample the volume of air determined in A.4.4, as a minimum, for each sample at each
sampling location.
A.5.5 If an out-of-specification count is found at a location due to an identified abnormal occurrence,
then that count can be discarded and noted as such on the test report and a new sample taken.
A.5.6 If an out-of-specification count found at a location is attributed to a technical failure of the
cleanroom or equipment, then the cause should be identified, remedial action taken and retesting
performed of the failed sampling location, the immediate surrounding locations and any other locations
affected. The choice shall be clearly documented and justified.
A.6 Processing of results
A.6.1 Recording of results
Record the result of each sample measurement as the number of particles in each single sample volume
at each of the considered particle size(s) appropriate to the relevant ISO Class of air cleanliness.
NOTE For particle counters with a concentration calculation mode, the manual evaluation may not be
necessary.
A.6.1.1 Average concentration of particles at each sampling location
When two or more single sample volumes are taken at a location, calculate and record the average
number of particles per location at each considered particle size from the individual sample particle
concentrations, according to Formula (A.3).
 
xx++ .x


ii.12 in.


x = (A.3)


i



 n
 
where
is the average number of particles at location i, representing any location;
x
i
x to x are the number of particles in individual samples;
i.1 i.n
n is the number of samples taken at location i.
A.6.1.2 Calculate the concentration per cubic metre
x ×1000
i
C = (A.4)
i
V
t
where
C is the concentration of particles per cubic metre;
i
is the average number of particles at location i, representing each location;
x
i
ISO 14644-1:2015(E)
V is the selected single sample volume in litres.
t
A.6.2 Interpretation of results
A.6.2.1 Classification requirements
The cleanroom or clean zone is deemed to have met the specified air cleanliness classification
requirements if the average of the particle co
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