ASTM F50-12(2015)
(Practice)Standard 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
Standard 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
SIGNIFICANCE AND USE
5.1 The primary purpose of this practice is to describe a procedure for collecting near real-time data on airborne particle concentration and size distribution in clean areas as indicated by single particle counting techniques. Implementation of some government and industry specifications requires acquisition of particle size and concentration data using an SPC.
5.2 The processing requirements of many products manufactured in a clean room involves environmental cleanliness levels so low that a single particle counter with capability for detecting very small particles is required to characterize clean room air. Real-time information on concentration of airborne particles in size ranges from less than 0.1 μm to 5 μm and greater can be obtained only with an SPC. Definition of particles larger than approximately 0.05 μm may be carried out with direct measurement of light scattering from individual particles; other techniques may be required for smaller particles, such as preliminary growth by condensation before particle measurement.
5.3 Particle size data are referenced to the particle system used to calibrate the SPC. Differences in detection, electronic and sample handling systems among the various SPCs may contribute to differences in particle characterization. Care must be exercised in attempting to compare data from particles that vary significantly in composition or shape from the calibration base material. Variations may also occur between instruments using similar particle sensing systems with different operating parameters. These effects should be recognized and minimized by using standard methods for SPC calibration and operation.
5.4 In applying this practice, the fundamental assumption is made that the particles in the sample passing through the SPC are representative of the particles in the entire dust-controlled area being analyzed. Care is required that good sampling procedures are used and that no artifacts are produced at any point in the samp...
SCOPE
1.1 This practice covers the determination of the particle concentration, by number, and the size distribution of airborne particles in dust-controlled areas and clean rooms, for particles in the size range of approximately 0.01 to 5.0 μm. Particle concentrations not exceeding 3.5 × 106 particles/m 3 (100 000/ft3) are covered for all particles equal to and larger than the minimum size measured.
1.2 This practice uses an airborne single particle counting device (SPC) whose operation is based on measuring the signal produced by an individual particle passing through the sensing zone. The signal must be directly or indirectly related to particle size.
Note 1: The SPC type is not specified here. The SPC can be a conventional optical particle counter (OPC), an aerodynamic particle sizer, a condensation nucleus counter (CNC) operating in conjunction with a diffusion battery or differential mobility analyzer, or any other device capable of counting and sizing single particles in the size range of concern and of sampling in a cleanroom environment.
1.3 Individuals performing tests in accordance with this practice shall be trained in use of the SPC and shall understand its operation.
1.4 Since the concentration and the particle size distribution of airborne particles are subject to continuous variations, the choice of sampling probe configuration, locations and sampling times will affect sampling results. Further, the differences in the physical measurement, electronic and sample handling systems between the various SPCs and the differences in physical properties of the various particles being measured can contribute to variations in the test results. These differences should be recognized and minimized by using a standard method of primary calibration and by minimizing variability of sample acquisition procedures.
1.5 Sample acquisition procedures and equipment may be selected for specific applications based on va...
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Designation: F50 − 12 (Reapproved 2015)
Standard 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
ThisstandardisissuedunderthefixeddesignationF50;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 Sample acquisition procedures and equipment may be
selected for specific applications based on varying cleanroom
1.1 This practice covers the determination of the particle
class levels. Firm requirements for these selections are beyond
concentration, by number, and the size distribution of airborne
thescopeofthispractice;however,samplingpracticesshallbe
particlesindust-controlledareasandcleanrooms,forparticles
stated that take into account potential spatial and statistical
in the size range of approximately 0.01 to 5.0 µm. Particle
6 3 variations of suspended particles in clean rooms.
concentrations not exceeding 3.5 × 10 particles/m
(100000⁄ft ) are covered for all particles equal to and larger
NOTE 2—General references to cleanroom classifications follow Fed-
eral Standard209E, latest revision. Where airborne particles are to be
than the minimum size measured.
characterized in dust-controlled areas that do not meet these
1.2 This practice uses an airborne single particle counting
classifications, the latest revision of the pertinent specification for these
device(SPC)whoseoperationisbasedonmeasuringthesignal
areas shall be used.
produced by an individual particle passing through the sensing
1.6 The values stated in SI units are to be regarded as the
zone. The signal must be directly or indirectly related to
standard. The values given in parentheses are provided for
particle size.
information only and are not considered standard.
NOTE 1—The SPC type is not specified here. The SPC can be a
1.7 This standard does not purport to address all of the
conventional optical particle counter (OPC), an aerodynamic particle
safety concerns, if any, associated with its use. It is the
sizer,acondensationnucleuscounter(CNC)operatinginconjunctionwith
responsibility of the user of this standard to establish appro-
a diffusion battery or differential mobility analyzer, or any other device
priate safety and health practices and determine the applica-
capableofcountingandsizingsingleparticlesinthesizerangeofconcern
and of sampling in a cleanroom environment. bility of regulatory limitations prior to use.Forspecifichazards
statements, see Section 8.
1.3 Individuals performing tests in accordance with this
practiceshallbetrainedinuseoftheSPCandshallunderstand
2. Referenced Documents
its operation.
2.1 ASTM Standards:
1.4 Sincetheconcentrationandtheparticlesizedistribution
D1356Terminology Relating to Sampling and Analysis of
of airborne particles are subject to continuous variations, the
Atmospheres
choice of sampling probe configuration, locations and sam-
F328Practice for Calibration of anAirborne Particle Coun-
plingtimeswillaffectsamplingresults.Further,thedifferences
ter Using Monodisperse Spherical Particles (Withdrawn
in the physical measurement, electronic and sample handling
2007)
systems between the various SPCs and the differences in
F649PracticeforSecondaryCalibrationofAirborneParticle
physicalpropertiesofthevariousparticlesbeingmeasuredcan
Counter Using Comparison Procedures (Withdrawn
contribute to variations in the test results. These differences
2007)
should be recognized and minimized by using a standard
F658Practice for Calibration of a Liquid-Borne Particle
methodofprimarycalibrationandbyminimizingvariabilityof
Counter Using an Optical System Based Upon Light
sample acquisition procedures.
1 2
This practice is under the jurisdiction of ASTM Committee E21 on Space For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Simulation andApplications of SpaceTechnology and is the direct responsibility of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Subcommittee E21.05 on Contamination. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2015. Published November 2015. Originally the ASTM website.
approved in 1965. Last previous edition approved in 2012 as F50–12. DOI: The last approved version of this historical standard is referenced on
10.1520/F0050-12R15. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F50 − 12 (2015)
Extinction (Withdrawn 2007) 3.1.6.1 Discussion—It can be quantified as the ratio of the
square root of the difference between the measured and actual
2.2 U.S. Federal Standard:
variances of a monosized particle size distribution to the mean
Federal Standard No. 209E,Clean Room and Work Station
4,5
diameter of those monosize particles, using procedures as
Requirements, Controlled Environment
shown in Practice F658.
2.3 Other Documents:
ISO 14644-1 Cleanrooms and Associated Controlled 3.1.7 standardization—secondary calibration of electronic
system voltage and signal response threshold levels using the
Environments, Classification of air cleanliness
ISO 14644-2 Cleanrooms and Associated Controlled reference system built into the SPC.
3.1.7.1 Discussion—TheSPCshouldbecapableofcarrying
Environments,Specificationsfortestingandmonitoringto
prove continued compliance with ISO 14644-1 out this procedure with a simple, rapid manual operation or by
internal timed or microprocessor controlled components.
3. Terminology
3.2 For definitions of other terms used in this practice, see
3.1 Definitions of Terms Specific to This Standard:
Terminology D1356 and (Federal Standard209E).
3.1.1 dust-controlled area—a clean room or clean work
4. Summary of Practice
space in which airborne and deposited particulate contamina-
tionlevels,orboth,arecontrolledonthebasisofadocumented
4.1 Satisfactory primary calibration within the manufactur-
standard such as Federal Standard209E.
er’s recommended time period and routine standardization
should be verified as a first step.
3.1.2 dynamic range—theparticlesizerange,expressedasa
multiple of the minimum measured size, over which the SPC
4.2 Asampleacquisitionprogramisestablishedonthebasis
can measure particles with size resolution of 10% or less.
of the cleanliness level that is to be verified or monitored.This
program will include sample point identification, sample size
3.1.3 particle concentration—the number of individual par-
definitions and sampling frequency, specification of the sam-
ticles per unit volume of ambient temperature and pressure air,
3 3
plerinletandsampletransportsystem,definitionoftheparticle
particles/m or particles/ft .
size ranges to be measured, and any other parameters of
3.1.4 particle size—equivalent diameter of a particle de-
concern in the dust-controlled area or clean room.
tected by an SPC.
4.3 AirsamplesarepassedthroughtheSPCandtheparticle
3.1.4.1 Discussion—Theequivalentdiameteristhediameter
ofareferencesphereofknownsizeandphysicalcharacteristics content of each sample is defined by the SPC. Particles
contained in the sampled air pass through the sensing zone of
(for example, refractive index when using an OPC; density
when using an aerodynamic particle sizer; etc) and generating the SPC. Each particle produces a signal that can be related to
particle size.An electronic system sorts and counts the pulses,
thesameresponseintheSPCsensingzoneastheparticlebeing
measured. Spherical particles are used for calibration of the registering the number of particles of various sizes that have
passedthroughthesensingzoneduringpassageofaknowngas
SPCs considered here.The SPC response is related to the size,
shape, orientation and physical properties of the particle volume. The concentration and particle size data can be
displayed, printed or otherwise processed, locally or remotely.
passing through the SPC sensing zone. If an optical particle
counter is used, the geometry of the optical system, as well as
5. Significance and Use
the spectral distribution of the illuminating light influences the
5.1 The primary purpose of this practice is to describe a
reported particle size. If a condensation nucleus counter with a
procedureforcollectingnearreal-timedataonairborneparticle
size-fractionationdeviceisused,theSPCoperatingparameters
concentration and size distribution in clean areas as indicated
and the particle properties that affect the nucleation efficiency
by single particle counting techniques. Implementation of
and, for example, the diffusion coefficient, will influence
some government and industry specifications requires acquisi-
reported data. The SPC instruction manual should make the
tion of particle size and concentration data using an SPC.
user aware of the effects of such factors on the indicated
particle size data.
5.2 The processing requirements of many products manu-
3.1.5 primary calibration—calibration with standard refer- factured in a clean room involves environmental cleanliness
ence particles for particle size and (optionally) concentration. levels so low that a single particle counter with capability for
Initially carried out by the SPC manufacturer. detecting very small particles is required to characterize clean
room air. Real-time information on concentration of airborne
3.1.6 resolution—the capability of the SPC to differentiate
particles in size ranges from less than 0.1 µm to 5 µm and
between particles with small difference in size.
greater can be obtained only with an SPC. Definition of
particleslargerthanapproximately0.05µmmaybecarriedout
with direct measurement of light scattering from individual
Available from U.S. General ServicesAdministration, Federal Supply Service,
Standardization Division, Washington, DC 20406, http://www.gsa.gov.
particles; other techniques may be required for smaller
Fed-Std-209EhasbeenreplacedbyISO/DIS14644-1and-2,butmaycontinue
particles, such as preliminary growth by condensation before
to be used by mutual agreement.
particle measurement.
Available from Institute of Environmental Sciences and Technology (IEST),
Arlington Place One, 2340 S.Arlington Heights Rd., Suite 100,Arlington Heights,
5.3 Particle size data are referenced to the particle system
IL 60005-4516, http://www.iest.org, and from International Organization for Stan-
used to calibrate the SPC. Differences in detection, electronic
dardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20,
Switzerland, http://www.iso.org. and sample handling systems among the various SPCs may
F50 − 12 (2015)
contributetodifferencesinparticlecharacterization.Caremust transit tube with dimensions so that residence time in the tube
be exercised in attempting to compare data from particles that willnotexceed10s.Sampletubesshouldbeconfiguredsothat
vary significantly in composition or shape from the calibration the flow Reynolds number is maintained in the range 5000 to
base material. Variations may also occur between instruments 25000. For particles in the size range 0.1 µm to ≈2µmin
3 3
using similar particle sensing systems with different operating diameter and a SPC flow rate of 0.028 m /min (1 ft /min), a
parameters.These effects should be recognized and minimized transit tube up to 30 m long can be used. For particles in the
by using standard methods for SPC calibration and operation. size range ≈ 2 µm to 10 µm, a maximum transit tube length of
3 m can be used. If a flexible transit tube is to be used, then no
5.4 In applying this practice, the fundamental assumption is
radius of curvature below 15 cm shall be used.
made that the particles in the sample passing through the SPC
7.1.2 Particle Sensing/Measurement Chamber—Defined by
are representative of the particles in the entire dust-controlled
the nature of the SPC that is used. It should be verified that
area being analyzed. Care is required that good sampling
minimum recirculation and recounting of particles occurs in
procedures are used and that no artifacts are produced at any
that chamber. If the particle characterization system includes
point in the sample handling and analysis process; these
any particle manipulation (for example, diffusion battery or
precautions are necessary both in verification and in operation
nucleation chamber, etc) before particle sensing occurs, then
of the SPC.
the SPC element that manipulates the particles shall not result
6. Interferences
in significant particle number change during that process.
6.1 Since the SPC is typically a high sensitivity device, it’s 7.1.3 Air Flow Metering of Control System, shall be located
after the particle sensing/measurement chamber so as to
response may be affected by internally or externally generated
noise. The SPC should not be operated at a sensitivity level so minimize particle losses or artifact generation before measure-
ment occurs.
high that internal noise produces more than 5% of the data
signals.
7.1.4 Exhaust System, may consist of either a built-in
vacuum source or an external vacuum supply. If the built-in
6.2 Precautions should also be taken to ensure that the test
vacuum source is used, then the exhaust stream from that
area environment does not exceed the radio frequency or
sourceshallbesuitablyfilteredsothatparticlessampledbyand
electromagnetic interference capabilities of the SPC.
internallygeneratedbytheSPC,orboth,arenotreturnedtothe
6.3 Operation at acceptably low levels of internal noise can
dust-controlled area.
be verified by drawing a sample into the SPC through a filter
7.2 Particle Characterization System, shall be capable of
orothergascleaningdevicethatwillpositivelyremoveatleast
both detecting and sizing the particles that are sampled by the
99.97% of all particles of size equal to and greater than that
SPC. The characterization system particle sizing resolution,
which the SPC will measure.After a short stabilization period,
expressed as a percentage, shall not exceed 10% over the
any signals reported by the SPC can be assumed to arise from
operating dynamic range.The SPC specifications shall include
internal or external noise sources.
information as to the maximum particle concentration that can
7. Apparatus
be measured before coincidence error > 10% of the indicated
7.1 SPC—The apparatus shall consist of a SPC, selected on particle count, occurs in the detection process. The specifica-
tions shall also define the pulse rate where the data processing
the basis of its ability to count and size single particles i
...
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: F50 − 12 F50 − 12 (Reapproved 2015)
Standard 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
This standard is issued under the fixed designation F50; 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 practice covers the determination of the particle concentration, by number, and the size distribution of airborne particles
in dust-controlled areas and clean rooms, for particles in the size range of approximately 0.01 to 5.0 μm. Particle concentrations
6 3 3
not exceeding 3.5 × 10 particles/m (100 000 ⁄ft ) are covered for all particles equal to and larger than the minimum size
measured.
1.2 This practice uses an airborne single particle counting device (SPC) whose operation is based on measuring the signal
produced by an individual particle passing through the sensing zone. The signal must be directly or indirectly related to particle
size.
NOTE 1—The SPC type is not specified here. The SPC can be a conventional optical particle counter (OPC), an aerodynamic particle sizer, a
condensation nucleus counter (CNC) operating in conjunction with a diffusion battery or differential mobility analyzer, or any other device capable of
counting and sizing single particles in the size range of concern and of sampling in a cleanroom environment.
1.3 Individuals performing tests in accordance with this practice shall be trained in use of the SPC and shall understand its
operation.
1.4 Since the concentration and the particle size distribution of airborne particles are subject to continuous variations, the choice
of sampling probe configuration, locations and sampling times will affect sampling results. Further, the differences in the physical
measurement, electronic and sample handling systems between the various SPCs and the differences in physical properties of the
various particles being measured can contribute to variations in the test results. These differences should be recognized and
minimized by using a standard method of primary calibration and by minimizing variability of sample acquisition procedures.
1.5 Sample acquisition procedures and equipment may be selected for specific applications based on varying cleanroom class
levels. Firm requirements for these selections are beyond the scope of this practice; however, sampling practices shall be stated
that take into account potential spatial and statistical variations of suspended particles in clean rooms.
NOTE 2—General references to cleanroom classifications follow Federal Standard 209E, latest revision. Where airborne particles are to be characterized
in dust-controlled areas that do not meet these classifications, the latest revision of the pertinent specification for these areas shall be used.
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are provided for information
only and are not considered standard.
1.7 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
limitations prior to use. For specific hazards statements, see Section 8.
2. Referenced Documents
2.1 ASTM Standards:
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
This practice 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, 2012Oct. 1, 2015. Published May 2012November 2015. Originally approved in 1965. Last previous edition approved in 20072012 as
F50 – 07.F50 – 12. DOI: 10.1520/F0050-12.10.1520/F0050-12R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F50 − 12 (2015)
F328 Practice for Calibration of an Airborne Particle Counter Using Monodisperse Spherical Particles (Withdrawn 2007)
F649 Practice for Secondary Calibration of Airborne Particle Counter Using Comparison Procedures (Withdrawn 2007)
F658 Practice for Calibration of a Liquid-Borne Particle Counter Using an Optical System Based Upon Light Extinction
(Withdrawn 2007)
2.2 U.S. Federal Standard:
4,5
Federal Standard No. 209E, Clean Room and Work Station Requirements, Controlled Environment
2.3 Other Documents:
ISO 14644-1 Cleanrooms and Associated Controlled Environments, Classification of air cleanliness
ISO 14644-2 Cleanrooms and Associated Controlled Environments, Specifications for testing and monitoring to prove continued
compliance with ISO 14644-1
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 dust-controlled area—a clean room or clean work space in which airborne and deposited particulate contamination levels,
or both, are controlled on the basis of a documented standard such as Federal Standard 209E.
3.1.2 dynamic range—the particle size range, expressed as a multiple of the minimum measured size, over which the SPC can
measure particles with size resolution of 10 % or less.
3.1.3 particle concentration—the number of individual particles per unit volume of ambient temperature and pressure air,
3 3
particles/m or particles/ft .
3.1.4 particle size—equivalent diameter of a particle detected by an SPC.
The last approved version of this historical standard is referenced on www.astm.org.
Available from U.S. General Services Administration, Federal Supply Service, Standardization Division, Washington, DC 20406, http://www.gsa.gov.
Fed-Std-209E has been replaced by ISO/DIS 14644-1 and -2, but may continue to be used by mutual agreement.
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, and from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland,
http://www.iso.org.
3.1.4.1 Discussion—
The equivalent diameter is the diameter of a reference sphere of known size and physical characteristics (for example, refractive
index when using an OPC; density when using an aerodynamic particle sizer; etc) and generating the same response in the SPC
sensing zone as the particle being measured. Spherical particles are used for calibration of the SPCs considered here. The SPC
response is related to the size, shape, orientation and physical properties of the particle passing through the SPC sensing zone. If
an optical particle counter is used, the geometry of the optical system, as well as the spectral distribution of the illuminating light
influences the reported particle size. If a condensation nucleus counter with a size-fractionation device is used, the SPC operating
parameters and the particle properties that affect the nucleation efficiency and, for example, the diffusion coefficient, will influence
reported data. The SPC instruction manual should make the user aware of the effects of such factors on the indicated particle size
data.
3.1.5 primary calibration—calibration with standard reference particles for particle size and (optionally) concentration. Initially
carried out by the SPC manufacturer.
3.1.6 resolution—the capability of the SPC to differentiate between particles with small difference in size.
3.1.6.1 Discussion—
It can be quantified as the ratio of the square root of the difference between the measured and actual variances of a monosized
particle size distribution to the mean diameter of those monosize particles, using procedures as shown in Practice F658.
3.1.7 standardization—secondary calibration of electronic system voltage and signal response threshold levels using the
reference system built into the SPC.
3.1.7.1 Discussion—
The SPC should be capable of carrying out this procedure with a simple, rapid manual operation or by internal timed or
microprocessor controlled components.
3.2 For definitions of other terms used in this practice, see Terminology D1356 and (Federal Standard 209E).
F50 − 12 (2015)
4. Summary of Practice
4.1 Satisfactory primary calibration within the manufacturer’s recommended time period and routine standardization should be
verified as a first step.
4.2 A sample acquisition program is established on the basis of the cleanliness level that is to be verified or monitored. This
program will include sample point identification, sample size definitions and sampling frequency, specification of the sampler inlet
and sample transport system, definition of the particle size ranges to be measured, and any other parameters of concern in the
dust-controlled area or clean room.
4.3 Air samples are passed through the SPC and the particle content of each sample is defined by the SPC. Particles contained
in the sampled air pass through the sensing zone of the SPC. Each particle produces a signal that can be related to particle size.
An electronic system sorts and counts the pulses, registering the number of particles of various sizes that have passed through the
sensing zone during passage of a known gas volume. The concentration and particle size data can be displayed, printed or otherwise
processed, locally or remotely.
5. Significance and Use
5.1 The primary purpose of this practice is to describe a procedure for collecting near real-time data on airborne particle
concentration and size distribution in clean areas as indicated by single particle counting techniques. Implementation of some
government and industry specifications requires acquisition of particle size and concentration data using an SPC.
5.2 The processing requirements of many products manufactured in a clean room involves environmental cleanliness levels so
low that a single particle counter with capability for detecting very small particles is required to characterize clean room air.
Real-time information on concentration of airborne particles in size ranges from less than 0.1 μm to 5 μm and greater can be
obtained only with an SPC. Definition of particles larger than approximately 0.05 μm may be carried out with direct measurement
of light scattering from individual particles; other techniques may be required for smaller particles, such as preliminary growth by
condensation before particle measurement.
5.3 Particle size data are referenced to the particle system used to calibrate the SPC. Differences in detection, electronic and
sample handling systems among the various SPCs may contribute to differences in particle characterization. Care must be exercised
in attempting to compare data from particles that vary significantly in composition or shape from the calibration base material.
Variations may also occur between instruments using similar particle sensing systems with different operating parameters. These
effects should be recognized and minimized by using standard methods for SPC calibration and operation.
5.4 In applying this practice, the fundamental assumption is made that the particles in the sample passing through the SPC are
representative of the particles in the entire dust-controlled area being analyzed. Care is required that good sampling procedures are
used and that no artifacts are produced at any point in the sample handling and analysis process; these precautions are necessary
both in verification and in operation of the SPC.
6. Interferences
6.1 Since the SPC is typically a high sensitivity device, it’s response may be affected by internally or externally generated noise.
The SPC should not be operated at a sensitivity level so high that internal noise produces more than 5 % of the data signals.
6.2 Precautions should also be taken to ensure that the test area environment does not exceed the radio frequency or
electromagnetic interference capabilities of the SPC.
6.3 Operation at acceptably low levels of internal noise can be verified by drawing a sample into the SPC through a filter or
other gas cleaning device that will positively remove at least 99.97 % of all particles of size equal to and greater than that which
the SPC will measure. After a short stabilization period, any signals reported by the SPC can be assumed to arise from internal
or external noise sources.
7. Apparatus
7.1 SPC—The apparatus shall consist of a SPC, selected on the basis of its ability to count and size single particles in the
required size range. The SPC shall include a sample air flow system, a particle characterization system, and a data processing
system. The minimum measurable particle size shall be selected from the clean area definition stated in ISO 14644-1 (Table I of
Federal Standard 209E), or from a different specification of clean-area airborne particle concentration at a stated minimum particle
size. For classification levels based on measurement of particles larger than 0.05 μm, an optical particle counter (OPC), an
aerodynamic particle sizer or an equivalent SPC can be used. For classification levels based on particles less than 0.05 μm, a CNC
in combination with a diffusion battery, a differential mobility analyzer or an equivalent SPC can be used.
7.1.1 Sample Air Flow System, consists of an intake tube, the particle sensing/measurement chamber, an air flow metering or
control system, and an exhaust system. No abrupt transitions in dimension should occur within the air flow system. The inlet tube
should consist of a sharp-edged inlet nozzle connected to a tube that will transport the sample air to the particle characterization
system. The sample inlet nozzle should have a cross-sectional area equivalent to that of a circle of diameter at least 2 mm. The
F50 − 12 (2015)
nozzle can be attached to a transit tube with dimensions so that residence time in the tube will
...
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