ASTM F25/F25M-09(2015)

Standard Test Method for Sizing and Counting Airborne Particulate Contamination in Cleanrooms and Other Dust-Controlled Areas

ABSTRACT
This test method covers the apparatuses required, sampling methods, standard procedures and calculations, and test reports for counting and sizing airborne microparticulate matter, the sampling areas for which are specifically those with contamination levels typical of cleanrooms and dust-controlled areas. The test method is based on the microscopical examination of particles impinged upon a membrane filter with the aid of a vacuum. Sampling may be done in a cleanroom, clean zone, or other controlle areas, or in a duct or pipe, wherein the number of sampling points is proportional to the floor area of the enclosure to be checked. The apparatus and facilities required are typical of a laboratory for the study of macroparticle contamination. The operator must have adequate basic training in microscopy and the techniques of particle sizing and counting.
SCOPE
1.1 This test method covers counting and sizing airborne particulate matter 5 µm and larger (macroparticles). The sampling areas are specifically those with contamination levels typical of cleanrooms and dust-controlled areas.  
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.

General Information

• Status: Historical
• Publication Date: 30-Sep-2015
• ICS: 13.040.30 - Workplace atmospheres
• Technical Committee: E21 - Space Simulation and Applications of Space Technology
• Drafting Committee: E21.05 - Contamination

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F25/F25M − 09 (Reapproved 2015)
Standard Test Method for
Sizing and Counting Airborne Particulate Contamination in
Cleanrooms and Other Dust-Controlled Areas
This standard is issued under the fixed designation F25/F25M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.3 IEST Document:
IEST-G-CC1003Measurement of Airborne Macroparticles
1.1 This test method covers counting and sizing airborne
(1999)
particulate matter 5 µm and larger (macroparticles). The
2.4 SAE Document:
samplingareasarespecificallythosewithcontaminationlevels
SAEAbstractARP-743, Procedure for the Determination of
typical of cleanrooms and dust-controlled areas.
Particulate Contamination of Air in Dust-Controlled
1.2 The values stated in either SI units or inch-pound units
Spaces by Particle Count Method, August 1962
are to be regarded separately as standard. The values stated in
each system may not be exact equivalents; therefore, each
3. Terminology
system shall be used independently of the other. Combining
3.1 Definitions:
values from the two systems may result in non-conformance
3.1.1 airflow:
with the standard.
3.1.1.1 unidirectional airflow—airflowwhichhasasingular
1.3 This standard does not purport to address all of the
direction of flow and may or may not contain uniform
safety concerns, if any, associated with its use. It is the
velocities of air flow along parallel lines.
responsibility of the user of this standard to establish appro-
NOTE 1—Formerly known as laminar airflow.
priate safety and health practices and determine the applica-
3.1.1.2 non-unidirectional airflow—air distribution where
bility of regulatory requirements prior to use.
the supply air entering the room mixes with the internal air by
2. Referenced Documents
means of induction.
2.1 ASTM Standards:
3.1.2 critical pressure—for an orifice, with a constant up-
F50Practice for Continuous Sizing and Counting of Air-
stream pressure, the downstream pressure at which the flow
borne Particles in Dust-Controlled Areas and Clean
will not increase when the downstream pressure decreases.
Rooms Using Instruments Capable of Detecting Single
3.1.3 critical pressure ratio—the ratio of the critical pres-
Sub-Micrometre and Larger Particles
sure of an orifice to the entrance pressure.
2.2 ISO Standard:
3.1.4 customer—organization, or the agent thereof, respon-
ISO 14644-1 Cleanrooms and Associated Controlled
3 sible for specifying the requirements of a cleanroom or clean
Environments—Part 1: Classification of Air Cleanliness
zone.
3.1.5 fiber—particlehavinganaspect(length-to-width)ratio
This test method is under the jurisdiction of ASTM Committee E21 on Space
of 10 or more.
Simulation andApplications of SpaceTechnology and is the direct responsibility of
Subcommittee E21.05 on Contamination.
3.1.6 macroparticle—particle with an equivalent diameter
Current edition approved Oct. 1, 2015. Published November 2015. Originally
greater than 5 µm.
approved in 1963. Last previous edition approved in 2009 as F25–09. DOI:
10.1520/F0025_F0025M-09R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from Institute of Environmental Sciences and Technology (IEST),
Standards volume information, refer to the standard’s Document Summary page on Arlington Place One, 2340 S.Arlington Heights Rd., Suite 100,Arlington Heights,
the ASTM website. IL 60005-4516, http://www.iest.org.
3 5
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., Available from Society of Automotive Engineers (SAE), 400 Commonwealth
4th Floor, New York, NY 10036, http://www.ansi.org. Dr., Warrendale, PA 15096-0001, http://www.sae.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F25/F25M − 09 (2015)
FIG. 2 Typical Air Sampling-Filtration Apparatus
5. Apparatus
5.1 Filter Holder, aerosol open type having an effective
FIG. 1 Suitable Microscope: Inclined Binocular Body; Mechanical
filtering area of 960 6 25 mm .
Stage; Triple Nosepiece; Ocular-Objective Combination to Obtain
40 to 45× and 90 to 150× Magnification 7
5.2 Adapter.
5.3 Flow-Limiting Orifice, 10 L/min.
3.1.7 M descriptor—measured or specified concentration of
5.4 Membrane Filters, black, 0.80-µm mean pore size,
macroparticlespercubicmetreofair,expressedintermsofthe
47-mmdiameter,withimprintedgridsquareshavingsides3.10
equivalent diameter that is characteristic of the measurement
6 0.08 mm. Pressure drop across the filter used shall be no
method used.
greater than 50 torr for an air flow rate of 1 L/min·cm .
3.1.7.1 Discussion—The M descriptor may be regarded as
5.5 Forceps, with unserrated tips.
an upper limit for the averages at sampling locations (or as an
upper confidence limit, depending upon the number of sam-
5.6 Vacuum Pump, capable of producing a pressure of 34
pling locations used to characterize the cleanroom or clean
kPa (260 torr) (vacuum of 500 torr) downstream of the orifice
zone). M descriptors cannot be used to define airborne particu-
at a flow rate of 10 L/min through the orifice.
late cleanliness classes, but they may be quoted independently
5.7 Flowmeter,calibratedandhavingacapacityinexcessof
or in conjunction with airborne particulate cleanliness classes.
10 L/min.
3.1.8 occupancy states:
5.8 Glass Microscope Slides, 50 mm by 75 mm, or 47-mm
3.1.8.1 as-built—condition where the installation is com-
plastic disposable petri dishes.
plete with all services connected and functioning but with no
additional equipment, materials, or personnel present.
3.1.8.2 at-rest—condition where the installation is complete
The sole source of supply of the apparatus known to the committee at this time
with equipment installed and operating in a manner agreed
is 47 mm Stainless Steel, Millipore XX5004710, available from Millipore
upon by the customer and supplier, but with no personnel
Corporation,290ConcordRd.,Billerica,MA01821.Ifyouareawareofalternative
present. suppliers, please provide this information to ASTM International Headquarters.
Your comments will receive careful consideration at a meeting of the responsible
3.1.8.3 operational—condition where the installation is 1
technical committee, which you may attend.
functioning in the specified manner, with the specified number The sole source of supply of the apparatus known to the committee at this time
1 3
is Luer slip to ⁄4 in. - ⁄8 in. ID hose Stainless Steel, XX6200004, available from
of personnel present and working in the manner agreed upon.
Millipore Corporation, 290 Concord Rd., Billerica, MA01821. If you are aware of
3.1.9 particle size—major projected dimension of the par-
alternative suppliers, please provide this information to ASTM International
Headquarters.Your comments will receive careful consideration at a meeting of the
ticle.
responsible technical committee, which you may attend.
The sole source of supply of the apparatus known to the committee at this time
4. Summary of Test Method
is Limiting Orifice Set (5 orifices including 10 L/min), XX5000000, available from
Millipore Corporation, 290 Concord Rd., Billerica, MA01821. If you are aware of
4.1 The test method is based on the microscopical exami-
alternative suppliers, please provide this information to ASTM International
nation of particles impinged upon a membrane filter with the
Headquarters.Your comments will receive careful consideration at a meeting of the
aid of a vacuum. The number of sampling points is propor- 1
responsible technical committee, which you may attend.
tional to the floor area of the enclosure to be checked. The
The sole source of supply of the apparatus known to the committee at this time
is AABG04700, Black Grid, 0.80 µm, available from Millipore Corporation, 290
apparatus and facilities required are typical of a laboratory for
Concord Rd., Billerica, MA01821. If you are aware of alternative suppliers, please
the study of macroparticle contamination. The operator must
provide this information toASTM International Headquarters.Your comments will
have adequate basic training in microscopy and the techniques
receive careful consideration at a meeting of the responsible technical committee,
of particle sizing and counting. which you may attend.
F25/F25M − 09 (2015)
5.9 Binocular Microscope, (Fig. 1) with ocular-objective 7.2 The filter surface may be vertical or horizontal with
combinations to obtain 40 to 45× and 90 to 150× magnifica- respect to the floor.
tions. Latter objective shall have numerical aperture of 0.15 7.2.1 The orientation of the filter depends on airflow direc-
min. tion for unidirectional airflow areas.
10 7.2.1.1 Samplinginaunidirectionalairflowshallbeasclose
5.10 Normal Counter, (2 gang) or equivalent.
to isokinetic as is possible.
5.11 Microscope Lamp, 6 V, 5 A, high-intensity.
7.2.1.2 IEST-G-CC1003 provides additional information on
5.12 Ocular Micrometer Scale, 5-mm linear scale with 100 isokinetic sampling.
7.2.2 For nonunidirectional airflow areas, the customer may
divisions.
specify an orientation or the process being monitored in the
5.13 Stage Micrometer, standard 0.01-mm to 0.1-mm scale.
cleanroom may indicate which orientation would be preferred.
7.2.2.1 In nonunidirectional airflow, airflow directions and
6. Sampling Apparatus
velocities vary with location and time.
6.1 The airborne particles shall be collected, with the aid of
7.2.2.2 IEST G-CC1003 recommends a sample inlet probe,
a vacuum source, on a membrane filter of 960-mm effective
with an inlet diameter of at least 20 mm, facing upward. This
filtering area.
will collect larger particles that tend to settle out of the air.
6.2 Theapparatusspecifiedin5.1,5.2,and5.3orequivalent
7.3 The standard sample for this test method shall be 300 L
shall be used.
(10 ft ).
6.3 Fig. 2 is picture of a typical sampler.
7.3.1 The sample size may be adjusted for specific condi-
tions.
6.4 Fig. 3 is a drawing of a typical sampler assembly.
7.3.2 The number of particles sampled shall meet statistical
6.5 Sampler airflow is maintained using the vacuum pump,
criteria of ISO 14644-1 or other accepted statistical sampling
specified in 5.6, connected to the sampler and either a
criteria.
flowmeter to measure flow or a calibrated orifice to control
7.4 The sample shall be taken at waist level [0.9 to 1.0 m
flow.
(36 to 40 in.)] from the floor), at bench level, or at other points
6.5.1 The flow rate may be adjusted using a flowmeter and
as specified by the customer. The sample points may be
valvedownstreamofthesamplerwithfilterandotherelements
selectedforrelevancetoandsensitivityoftheoperationsbeing
installed.
performed in the cleanroom.
6.5.2 A calibrated orifice, 5.3, may be used to control the
airflow rate. The specified flow rate for the orifice depends on
7.5 The number and location of sampling points shall be as
critical pressure ratio of less than 0.53 for air at room
designated in the sampling plan.
temperature and pressure. The limiting orifice shall be cali-
7.5.1 Theminimumnumberofsamplelocationsasspecified
brated with the pump, filter holder, and filter used for this test
in ISO 14644-1, Annex B may be used:
method. The required flow rate is 10 6 0.5 L/min.
N 5 =A (1)
L
6.6 Inspect the sampler, including the orifice, to ensure that
where:
itisfreeofrestrictingmatterbeforeeachtest.Cleanifrequired.
N = minimumnumberofsamplinglocations(roundedupto
L
7. Sampling in a Cleanroom, Clean Zone, or other
a whole number), and
Controlled Areas
A = area of the cleanroom or clean zone in square metres.
7.1 Sampling Plan:
7.1.1 A sampling plan shall be provided.
In the case of unidirectional horizontal airflow, the area A
7.1.2 ISO 14644-1 and IEST-G-CC1003 may be used as
may be considered as the cross section of the moving air
guides for the plan.
perpendicular to the direction of the airflow.
7.5.2 The nature of the operations or the customer may
select the number of sampling points.
Thesolesourceofsupplyoftheapparatusknowntothecommitteeatthistime
is the Veeder-Root counter, available from Veeder-Root, 6th Ave. & Burns Xing,
8. Sampling in a Duct or Pipe
Altoona, PA 16602. If you are aware of alternative suppliers, please provide this
8.1 The sampling of a moving gas stream in a duct or
information to ASTM International Headquarters. Your comments will receive
careful consideration at a meeting of the responsible technical committee, which
pipeline requires isokinetic sampling.
you may attend.
FIG. 3 Typical Aerosol Monitor Sampling System
F25/F25M − 09 (2015)
8.2 Often by reason of the total flow, the allowable pressure
drop, or the physical dimensions of the system (as for example
an air conditioning air duct), it is impracticable to sample the
entire flow.
8.3 Becauseofthelowviscosityofgas,movinggasstreams
present several special sampling problems, which may disturb
FIG. 5 Faulty Sample from a Rapid-Ducted Gas Stream
the results unless care is taken.
8.4 To collect a representative sample of particulate con-
8.10 Sampling rate and probe dimensions shall be carefully
tamination from a ducted air stream, insert a probe (as shown
adjusted to match duct and probe air velocities.
in Fig. 4) coupled to the sampling apparatus described in 5.1,
5.2, and 5.3.
9. Preparation of Apparatus
8.5 Achievingaccurateisokineticsamplingrequiresthatthe
9.1 Before sampling, remove dirt and dust from the filter
gas linear velocity at the probe opening match that in the duct.
holder by washing in a free-rinsing detergent, ketone-free
Equalvelocitiesmaybeachievedbyaproperratiobetweenthe
isopropyl alcohol, submicron-filtered reagent grade petroleum
probe opening and the limiting orifice dimensions, for ex-
ether (boiling range 30 to 60°C) or trichloromonofluorometh-
ample:
ane or trichlorotrifluoroethane.
flowinduct ~L/min! samplingrate ~L/min!
5 (2) 9.2 The clean laboratory equipment used for counting and
ductcross 2sectionalarea probeopeningarea
sizing the collected particles shall be in a HEPA-filtered clean
8.6 Failuretomatchtheprobeandductvelocitieswillcause
bench or equivalent clean area.
adistortionofresultsfavoringeitherlargeparticlesiftheprobe
9.3 Plastic microscope hoods shall be installed on the
velocitylowerthanductvelocityorsmallparticlesiftheprobe
microscope to minimize particle deposition on the filter being
velocity higher than duct velocity.
counted.
8.7 Fig. 5 shows an open-type holder installed in
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F25/F25M − 09 F25/F25M − 09 (Reapproved 2015)
Standard Test Method for
Sizing and Counting Airborne Particulate Contamination in
Cleanrooms and Other Dust-Controlled Areas
This standard is issued under the fixed designation F25/F25M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers counting and sizing airborne particulate matter 5 μm and larger (macroparticles). The sampling
areas are specifically those with contamination levels typical of cleanrooms and dust-controlled areas.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
requirements prior to use.
2. Referenced Documents
2.1 ASTM Standards:
F50 Practice for Continuous Sizing and Counting of Airborne Particles in Dust-Controlled Areas and Clean Rooms Using
Instruments Capable of Detecting Single Sub-Micrometre and Larger Particles
2.2 ISO Standard:
ISO 14644-1 Cleanrooms and Associated Controlled Environments—Part 1: Classification of Air Cleanliness
2.3 IEST Document:
IEST-G-CC1003 Measurement of Airborne Macroparticles (1999)
2.4 SAE Document:
SAE Abstract ARP-743, Procedure for the Determination of Particulate Contamination of Air in Dust-Controlled Spaces by
Particle Count Method, August 1962
3. Terminology
3.1 Definitions:
3.1.1 airflow:
3.1.1.1 unidirectional airflow—air flow which has a singular direction of flow and may or may not contain uniform velocities
of air flow along parallel lines.
NOTE 1—Formerly known as laminar airflow.
3.1.1.2 non-unidirectional airflow—air distribution where the supply air entering the room mixes with the internal air by means
of induction.
3.1.2 critical pressure—for an orifice, with a constant upstream pressure, the downstream pressure at which the flow will not
increase when the downstream pressure decreases.
This test method is under the jurisdiction of ASTM Committee E21 on Space Simulation and Applications of Space Technology and is the direct responsibility of
Subcommittee E21.05 on Contamination.
Current edition approved April 1, 2009Oct. 1, 2015. Published April 2009November 2015. Originally approved in 1963. Last previous edition approved in 20042009 as
F25 – 04.F25 – 09. DOI: 10.1520/F0025_F0025M-09.10.1520/F0025_F0025M-09R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Available from Institute of Environmental Sciences and Technology (IEST), Arlington Place One, 2340 S. Arlington Heights Rd., Suite 100, Arlington Heights, IL
60005-4516, http://www.iest.org.
Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F25/F25M − 09 (2015)
3.1.3 critical pressure ratio—the ratio of the critical pressure of an orifice to the entrance pressure.
3.1.4 customer—organization, or the agent thereof, responsible for specifying the requirements of a cleanroom or clean zone.
3.1.5 fiber—particle having an aspect (length-to-width) ratio of 10 or more.
3.1.6 macroparticle—particle with an equivalent diameter greater than 5 μm.
3.1.7 M descriptor—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.
3.1.7.1 Discussion—
The M descriptor may be regarded as an upper limit for the averages at sampling locations (or as an upper confidence limit,
depending upon the number of sampling locations used to characterize the cleanroom or clean zone). M descriptors cannot be used
to define airborne particulate cleanliness classes, but they may be quoted independently or in conjunction with airborne particulate
cleanliness classes.
3.1.8 occupancy states:
3.1.8.1 as-built—condition where the installation is complete with all services connected and functioning but with no additional
equipment, materials, or personnel present.
3.1.8.2 at-rest—condition where the installation is complete with equipment installed and operating in a manner agreed upon
by the customer and supplier, but with no personnel present.
3.1.8.3 operational—condition where the installation is functioning in the specified manner, with the specified number of
personnel present and working in the manner agreed upon.
3.1.9 particle size—major projected dimension of the particle.
4. Summary of Test Method
4.1 The test method is based on the microscopical examination of particles impinged upon a membrane filter with the aid of
a vacuum. The number of sampling points is proportional to the floor area of the enclosure to be checked. The apparatus and
facilities required are typical of a laboratory for the study of macroparticle contamination. The operator must have adequate basic
training in microscopy and the techniques of particle sizing and counting.
FIG. 1 Suitable Microscope: Inclined Binocular Body; Mechanical Stage; Triple Nosepiece; Ocular-Objective Combination to Obtain 40
to 45× and 90 to 150× Magnification
F25/F25M − 09 (2015)
FIG. 2 Typical Air Sampling-Filtration Apparatus
5. Apparatus
6 2
5.1 Filter Holder, aerosol open type having an effective filtering area of 960 6 25 mm .
5.2 Adapter.
5.3 Flow-Limiting Orifice, 10 L/min.
5.4 Membrane Filters, black, 0.80-μm mean pore size, 47-mm diameter, with imprinted grid squares having sides 3.10 6 0.08
mm. Pressure drop across the filter used shall be no greater than 50 torr for an air flow rate of 1 L/min·cm .
5.5 Forceps, with unserrated tips.
5.6 Vacuum Pump, capable of producing a pressure of 34 kPa (260 torr) (vacuum of 500 torr) downstream of the orifice at a
flow rate of 10 L/min through the orifice.
5.7 Flowmeter, calibrated and having a capacity in excess of 10 L/min.
5.8 Glass Microscope Slides, 50 mm by 75 mm, or 47-mm plastic disposable petri dishes.
5.9 Binocular Microscope, (Fig. 1) with ocular-objective combinations to obtain 40 to 45× and 90 to 150× magnifications. Latter
objective shall have numerical aperture of 0.15 min.
5.10 Normal Counter, (2 gang) or equivalent.
5.11 Microscope Lamp, 6 V, 5 A, high-intensity.
5.12 Ocular Micrometer Scale, 5-mm linear scale with 100 divisions.
5.13 Stage Micrometer, standard 0.01-mm to 0.1-mm scale.
6. Sampling Apparatus
6.1 The airborne particles shall be collected, with the aid of a vacuum source, on a membrane filter of 960-mm effective
filtering area.
6.2 The apparatus specified in 5.1, 5.2, and 5.3 or equivalent shall be used.
6.3 Fig. 2 is picture of a typical sampler.
6.4 Fig. 3 is a drawing of a typical sampler assembly.
The sole source of supply of the apparatus known to the committee at this time is 47 mm Stainless Steel, Millipore XX5004710, available from Millipore Corporation,
290 Concord Rd., Billerica, MA 01821. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will
receive careful consideration at a meeting of the responsible technical committee, which you may attend.
7 1 3
The sole source of supply of the apparatus known to the committee at this time is Luer slip to ⁄4 in. - ⁄8 in. ID hose Stainless Steel, XX6200004, available from Millipore
Corporation, 290 Concord Rd., Billerica, MA 01821. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your
comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
The sole source of supply of the apparatus known to the committee at this time is Limiting Orifice Set (5 orifices including 10 L/min), XX5000000, available from
Millipore Corporation, 290 Concord Rd., Billerica, MA 01821. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters.
Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
The sole source of supply of the apparatus known to the committee at this time is AABG04700, Black Grid, 0.80 μm, available from Millipore Corporation, 290 Concord
Rd., Billerica, MA 01821. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful
consideration at a meeting of the responsible technical committee, which you may attend.
The sole source of supply of the apparatus known to the committee at this time is the Veeder-Root counter, available from Veeder-Root, 6th Ave. & Burns Xing, Altoona,
PA 16602. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration
at a meeting of the responsible technical committee, which you may attend.
F25/F25M − 09 (2015)
FIG. 3 Typical Aerosol Monitor Sampling System
6.5 Sampler airflow is maintained using the vacuum pump, specified in 5.6, connected to the sampler and either a flowmeter
to measure flow or a calibrated orifice to control flow.
6.5.1 The flow rate may be adjusted using a flowmeter and valve downstream of the sampler with filter and other elements
installed.
6.5.2 A calibrated orifice, 5.3, may be used to control the airflow rate. The specified flow rate for the orifice depends on critical
pressure ratio of less than 0.53 for air at room temperature and pressure. The limiting orifice shall be calibrated with the pump,
filter holder, and filter used for this test method. The required flow rate is 10 6 0.5 L/min.
6.6 Inspect the sampler, including the orifice, to ensure that it is free of restricting matter before each test. Clean if required.
7. Sampling in a Cleanroom, Clean Zone, or other Controlled Areas
7.1 Sampling Plan:
7.1.1 A sampling plan shall be provided.
7.1.2 ISO 14644-1 and IEST-G-CC1003 may be used as guides for the plan.
7.2 The filter surface may be vertical or horizontal with respect to the floor.
7.2.1 The orientation of the filter depends on airflow direction for unidirectional airflow areas.
7.2.1.1 Sampling in a unidirectional airflow shall be as close to isokinetic as is possible.
7.2.1.2 IEST-G-CC1003 provides additional information on isokinetic sampling.
7.2.2 For nonunidirectional airflow areas, the customer may specify an orientation or the process being monitored in the
cleanroom may indicate which orientation would be preferred.
7.2.2.1 In nonunidirectional airflow, airflow directions and velocities vary with location and time.
7.2.2.2 IEST G-CC1003 recommends a sample inlet probe, with an inlet diameter of at least 20 mm, facing upward. This will
collect larger particles that tend to settle out of the air.
7.3 The standard sample for this test method shall be 300 L (10 ft ).
7.3.1 The sample size may be adjusted for specific conditions.
7.3.2 The number of particles sampled shall meet statistical criteria of ISO 14644-1 or other accepted statistical sampling
criteria.
7.4 The sample shall be taken at waist level [0.9 to 1.0 m (36 to 40 in.)] from the floor), at bench level, or at other points as
specified by the customer. The sample points may be selected for relevance to and sensitivity of the operations being performed
in the cleanroom.
7.5 The number and location of sampling points shall be as designated in the sampling plan.
7.5.1 The minimum number of sample locations as specified in ISO 14644-1, Annex B may be used:
N 5=A (1)
L
where:
N = minimum number of sampling locations (rounded up to a whole number), and
L
A = area of the cleanroom or clean zone in square metres.
In the case of unidirectional horizontal airflow, the area A may be considered as the cross section of the moving air perpendicular
to the direction of the airflow.
7.5.2 The nature of the operations or the customer may select the number of sampling points.
8. Sampling in a Duct or Pipe
8.1 The sampling of a moving gas stream in a duct or pipeline requires isokinetic sampling.
8.2 Often by reason of the total flow, the allowable pressure drop, or the physical dimensions of the system (as for example an
air conditioning air duct), it is impracticable to sample the entire flow.
8.3 Because of the low viscosity of gas, moving gas streams present several special sampling problems, which may disturb the
results unless care is taken.
F25/F25M − 09 (2015)
8.4 To collect a representative sample of particulate contamination from a ducted air stream, insert a probe (as shown in Fig.
4) coupled to the sampling apparatus described in 5.1, 5.2, and 5.3.
8.5 Achieving accurate isokinetic sampling requires that the gas linear velocity at the probe opening match that in the duct.
Equal velocities may be achieved by a proper ratio between the probe opening and the limiting orifice dimensions, for example:
flow in duct L/min sampling rate L/min
~ ! ~ !
5 (2)
duct cross 2 sectional area probe opening area
8.6 Failure to match the probe and duct velocities will cause a distortion of results favoring either large particles if the probe
velocity lower than duct velocity or small particles if the probe velocity higher than duct velocity.
8.7 Fig. 5 shows an open-type holder installed in a duct. Some large particles are diverted from the filter by airflow around the
filter holder. Most small particles are dive
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