1、Designation: F50 12 (Reapproved 2015)Standard Practice forContinuous Sizing and Counting of Airborne Particles inDust-Controlled Areas and Clean Rooms Using InstrumentsCapable of Detecting Single Sub-Micrometre and LargerParticles1This standard is issued under the fixed designation F50; the number i
2、mmediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This
3、practice covers the determination of the particleconcentration, by number, and the size distribution of airborneparticles in dust-controlled areas and clean rooms, for particlesin the size range of approximately 0.01 to 5.0 m. Particleconcentrations not exceeding 3.5 106particles/m3(100 000ft3) are
4、covered for all particles equal to and largerthan the minimum size measured.1.2 This practice uses an airborne single particle countingdevice (SPC) whose operation is based on measuring the signalproduced by an individual particle passing through the sensingzone. The signal must be directly or indir
5、ectly related toparticle size.NOTE 1The SPC type is not specified here. The SPC can be aconventional optical particle counter (OPC), an aerodynamic particlesizer, a condensation nucleus counter (CNC) operating in conjunction witha diffusion battery or differential mobility analyzer, or any other dev
6、icecapable of counting and sizing single particles in the size range of concernand of sampling in a cleanroom environment.1.3 Individuals performing tests in accordance with thispractice shall be trained in use of the SPC and shall understandits operation.1.4 Since the concentration and the particle
7、 size distributionof airborne particles are subject to continuous variations, thechoice of sampling probe configuration, locations and sam-pling times will affect sampling results. Further, the differencesin the physical measurement, electronic and sample handlingsystems between the various SPCs and
8、 the differences inphysical properties of the various particles being measured cancontribute to variations in the test results. These differencesshould be recognized and minimized by using a standardmethod of primary calibration and by minimizing variability ofsample acquisition procedures.1.5 Sampl
9、e acquisition procedures and equipment may beselected for specific applications based on varying cleanroomclass levels. Firm requirements for these selections are beyondthe scope of this practice; however, sampling practices shall bestated that take into account potential spatial and statisticalvari
10、ations of suspended particles in clean rooms.NOTE 2General references to cleanroom classifications follow Fed-eral Standard 209E, latest revision. Where airborne particles are to becharacterized in dust-controlled areas that do not meet theseclassifications, the latest revision of the pertinent spec
11、ification for theseareas shall be used.1.6 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are provided forinformation only and are not considered standard.1.7 This standard does not purport to address all of thesafety concerns, if any, associated wit
12、h its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardsstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D1356 Terminology Re
13、lating to Sampling and Analysis ofAtmospheresF328 Practice for Calibration of an Airborne Particle Coun-ter Using Monodisperse Spherical Particles (Withdrawn2007)3F649 Practice for Secondary Calibration ofAirborne ParticleCounter Using Comparison Procedures (Withdrawn2007)3F658 Practice for Calibrat
14、ion of a Liquid-Borne ParticleCounter Using an Optical System Based Upon Light1This practice is under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology and is the direct responsibility ofSubcommittee E21.05 on Contamination.Current edition approved Oct. 1
15、, 2015. Published November 2015. Originallyapproved in 1965. Last previous edition approved in 2012 as F50 12. DOI:10.1520/F0050-12R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume inf
16、ormation, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Extinction (Withdrawn 2007)3
17、2.2 U.S. Federal Standard:Federal Standard No. 209E, Clean Room and Work StationRequirements, Controlled Environment4,52.3 Other Documents:6ISO 14644-1 Cleanrooms and Associated ControlledEnvironments, Classification of air cleanlinessISO 14644-2 Cleanrooms and Associated ControlledEnvironments, Spe
18、cifications for testing and monitoring toprove continued compliance with ISO 14644-13. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 dust-controlled areaa clean room or clean workspace in which airborne and deposited particulate contamina-tion levels, or both, are controlled on
19、 the basis of a documentedstandard such as Federal Standard 209E.3.1.2 dynamic rangethe particle size range, expressed as amultiple of the minimum measured size, over which the SPCcan measure particles with size resolution of 10 % or less.3.1.3 particle concentrationthe number of individual par-ticl
20、es per unit volume of ambient temperature and pressure air,particles/m3or particles/ft3.3.1.4 particle sizeequivalent diameter of a particle de-tected by an SPC.3.1.4.1 DiscussionThe equivalent diameter is the diameterof a reference sphere of known size and physical characteristics(for example, refr
21、active index when using an OPC; densitywhen using an aerodynamic particle sizer; etc) and generatingthe same response in the SPC sensing zone as the particle beingmeasured. Spherical particles are used for calibration of theSPCs considered here. The SPC response is related to the size,shape, orienta
22、tion and physical properties of the particlepassing through the SPC sensing zone. If an optical particlecounter is used, the geometry of the optical system, as well asthe spectral distribution of the illuminating light influences thereported particle size. If a condensation nucleus counter with asiz
23、e-fractionation device is used, the SPC operating parametersand the particle properties that affect the nucleation efficiencyand, for example, the diffusion coefficient, will influencereported data. The SPC instruction manual should make theuser aware of the effects of such factors on the indicatedp
24、article size data.3.1.5 primary calibrationcalibration with standard refer-ence particles for particle size and (optionally) concentration.Initially carried out by the SPC manufacturer.3.1.6 resolutionthe capability of the SPC to differentiatebetween particles with small difference in size.3.1.6.1 D
25、iscussionIt can be quantified as the ratio of thesquare root of the difference between the measured and actualvariances of a monosized particle size distribution to the meandiameter of those monosize particles, using procedures asshown in Practice F658.3.1.7 standardizationsecondary calibration of e
26、lectronicsystem voltage and signal response threshold levels using thereference system built into the SPC.3.1.7.1 DiscussionThe SPC should be capable of carryingout this procedure with a simple, rapid manual operation or byinternal timed or microprocessor controlled components.3.2 For definitions of
27、 other terms used in this practice, seeTerminology D1356 and (Federal Standard 209E).4. Summary of Practice4.1 Satisfactory primary calibration within the manufactur-ers recommended time period and routine standardizationshould be verified as a first step.4.2 Asample acquisition program is establish
28、ed on the basisof the cleanliness level that is to be verified or monitored. Thisprogram will include sample point identification, sample sizedefinitions and sampling frequency, specification of the sam-pler inlet and sample transport system, definition of the particlesize ranges to be measured, and
29、 any other parameters ofconcern in the dust-controlled area or clean room.4.3 Air samples are passed through the SPC and the particlecontent of each sample is defined by the SPC. Particlescontained in the sampled air pass through the sensing zone ofthe SPC. Each particle produces a signal that can b
30、e related toparticle size. An electronic system sorts and counts the pulses,registering the number of particles of various sizes that havepassed through the sensing zone during passage of a known gasvolume. The concentration and particle size data can bedisplayed, printed or otherwise processed, loc
31、ally or remotely.5. Significance and Use5.1 The primary purpose of this practice is to describe aprocedure for collecting near real-time data on airborne particleconcentration and size distribution in clean areas as indicatedby single particle counting techniques. Implementation ofsome government an
32、d industry specifications requires acquisi-tion of particle size and concentration data using an SPC.5.2 The processing requirements of many products manu-factured in a clean room involves environmental cleanlinesslevels so low that a single particle counter with capability fordetecting very small p
33、articles is required to characterize cleanroom air. Real-time information on concentration of airborneparticles in size ranges from less than 0.1 m to 5 m andgreater can be obtained only with an SPC. Definition ofparticles larger than approximately 0.05 m may be carried outwith direct measurement of
34、 light scattering from individualparticles; other techniques may be required for smallerparticles, such as preliminary growth by condensation beforeparticle measurement.5.3 Particle size data are referenced to the particle systemused to calibrate the SPC. Differences in detection, electronicand samp
35、le handling systems among the various SPCs may4Available from U.S. General Services Administration, Federal Supply Service,Standardization Division, Washington, DC 20406, http:/www.gsa.gov.5Fed-Std-209E has been replaced by ISO/DIS 14644-1 and -2, but may continueto be used by mutual agreement.6Avai
36、lable 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 Stan-dardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20,
37、Switzerland, http:/www.iso.org.F50 12 (2015)2contribute to differences in particle characterization. Care mustbe exercised in attempting to compare data from particles thatvary significantly in composition or shape from the calibrationbase material. Variations may also occur between instrumentsusing
38、 similar particle sensing systems with different operatingparameters. These effects should be recognized and minimizedby using standard methods for SPC calibration and operation.5.4 In applying this practice, the fundamental assumption ismade that the particles in the sample passing through the SPCa
39、re representative of the particles in the entire dust-controlledarea being analyzed. Care is required that good samplingprocedures are used and that no artifacts are produced at anypoint in the sample handling and analysis process; theseprecautions are necessary both in verification and in operation
40、of the SPC.6. Interferences6.1 Since the SPC is typically a high sensitivity device, itsresponse may be affected by internally or externally generatednoise. The SPC should not be operated at a sensitivity level sohigh that internal noise produces more than 5 % of the datasignals.6.2 Precautions shou
41、ld also be taken to ensure that the testarea environment does not exceed the radio frequency orelectromagnetic interference capabilities of the SPC.6.3 Operation at acceptably low levels of internal noise canbe verified by drawing a sample into the SPC through a filteror other gas cleaning device th
42、at will positively remove at least99.97 % of all particles of size equal to and greater than thatwhich the SPC will measure. After a short stabilization period,any signals reported by the SPC can be assumed to arise frominternal or external noise sources.7. Apparatus7.1 SPCThe apparatus shall consis
43、t of a SPC, selected onthe basis of its ability to count and size single particles in therequired size range. The SPC shall include a sample air flowsystem, a particle characterization system, and a data process-ing system. The minimum measurable particle size shall beselected from the clean area de
44、finition stated in ISO 14644-1(Table I of Federal Standard 209E), or from a different speci-fication of clean-area airborne particle concentration at a statedminimum particle size. For classification levels based onmeasurement of particles larger than 0.05 m, an opticalparticle counter (OPC), an aer
45、odynamic particle sizer or anequivalent SPC can be used. For classification levels based onparticles less than 0.05 m, a CNC in combination with adiffusion battery, a differential mobility analyzer or an equiva-lent SPC can be used.7.1.1 Sample Air Flow System, consists of an intake tube,the particl
46、e sensing/measurement chamber, an air flow meter-ing or control system, and an exhaust system. No abrupttransitions in dimension should occur within the air flowsystem. The inlet tube should consist of a sharp-edged inletnozzle connected to a tube that will transport the sample air tothe particle ch
47、aracterization system. The sample inlet nozzleshould have a cross-sectional area equivalent to that of a circleof diameter at least 2 mm. The nozzle can be attached to atransit tube with dimensions so that residence time in the tubewill not exceed 10 s. Sample tubes should be configured so thatthe f
48、low Reynolds number is maintained in the range 5 000 to25 000. For particles in the size range 0.1 m to 2mindiameter and a SPC flow rate of 0.028 m3/min (1 ft3/min), atransit tube up to 30 m long can be used. For particles in thesize range 2 m to 10 m, a maximum transit tube length of3 m can be used
49、. If a flexible transit tube is to be used, then noradius of curvature below 15 cm shall be used.7.1.2 Particle Sensing/Measurement ChamberDefined bythe nature of the SPC that is used. It should be verified thatminimum recirculation and recounting of particles occurs inthat chamber. If the particle characterization system includesany particle manipulation (for example, diffusion battery ornucleation chamber, etc) before particle sensing occurs, thenthe SPC element that manipulates the particles shall not resultin significant particle number change
