ASTM F50-2007 Standard Practice for Continuous Sizing and Counting of Airborne Particles in Dust-Controlled Areas and Clean Rooms Using Instruments Capable of Detecting Single Sub-.pdf

1、Designation: F 50 07Standard 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 F 50; the number immediately follo

2、wing the designation indicates the year of originaladoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice co

3、vers 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 3 106particles/m3(100 000/ft3) are covered

4、for all particles equal to and larger than theminimum 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 indirectly re

5、lated 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 devicecapab

6、le 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 size di

7、stributionof 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 the dif

8、ferences 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 Sample acquis

9、ition 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 statisticalvariations o

10、f 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 these classifica-tions, the latest revision of the pertinent specificat

11、ion for these areas shallbe used.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with 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 limitat

12、ions prior to use. For specific hazardsstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D 1356 Terminology Relating to Sampling and Analysis ofAtmospheresF 328 Practice for Calibration of an Airborne ParticleCounter Using Monodisperse Spherical Particles3F 649 Practice for Second

13、ary Calibration of Airborne Par-ticle Counter Using Comparison Procedures3F 658 Practice for Calibration of a Liquid-Borne ParticleCounter Using an Optical System Based Upon LightExtinction32.2 U.S. Federal Standard:Federal Standard No. 209E, Clean Room and Work Station1This practice is under the ju

14、risdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology and is the direct responsibility ofSubcommittee E21.05 on Contamination.Current edition approved Nov. 1, 2007. Published November 2007. Originallyapproved in 1965. Last previous edition approved in 2001 as F 50

15、92 (2001)e12For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr

16、 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Requirements, Controlled Environment4,52.3 Other Documents:6ISO 14644-1 Cleanrooms and Associated Controlled Envi-ronments, Classification of air cleanlinessISO 14644-2 Cleanrooms and Associated Controlled Envi-ronments, Spe

17、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

18、 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

19、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 diam-eter of a reference sphere of known size and physical charac-teristics (for example,

20、refractive index when using an OPC;density when using an aerodynamic particle sizer; etc) andgenerating the same response in the SPC sensing zone as theparticle being measured. Spherical particles are used forcalibration of the SPCs considered here. The SPC response isrelated to the size, shape, ori

21、entation and physical properties ofthe particle passing through the SPC sensing zone. If an opticalparticle counter is used, the geometry of the optical system, aswell as the spectral distribution of the illuminating lightinfluences the reported particle size. If a condensation nucleuscounter with a

22、 size-fractionation device is used, the SPCoperating parameters and the particle properties that affect thenucleation efficiency and, for example, the diffusion coeffi-cient, will influence reported data. The SPC instruction manualshould make the user aware of the effects of such factors on theindic

23、ated particle 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

24、6.1 DiscussionIt 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 F 658.3.1.7 standardizationsecondary calibrati

25、on of electronicsystem 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 definit

26、ions of other terms used in this practice, seeTerminology D 1356 and ISO 14644-1(FederalStandard 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 pr

27、ogram is established 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 t

28、o be measured, and 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

29、 signal that can be 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 otherw

30、ise processed, locally 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 of

31、some government and 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 fordete

32、cting very small particles 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 dir

33、ect measurement of light scattering from individualparticles; other techniques may be required for smaller par-ticles, 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

34、 electronicand sample handling systems among the various SPCs maycontribute 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 bet

35、ween instrumentsusing similar particle sensing systems with different operating4Available from U.S. General Services Administration, Federal Supply Service,Standardization Division, Washington, DC 20406.5Fed-Std-209E has been replaced by ISO/DIS 14644-1 and -2, but may continueto be used by mutual a

36、greement.6Available from IEST, 940 E. Northwest Highway, Mt. Prospect, IL 60056 andthe International Organization for Standardization (ISO), 1 rue de Varemb, Casepostale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.chF50072parameters. These effects should be recognized and minimizedby using st

37、andard 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 SPCare representative of the particles in the entire dust-controlledarea being analyzed. Care is required that good samplingprocedure

38、s 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 operationof the SPC.6. Interferences6.1 Since the SPC is typically a high sensitivity device, itsresponse may be affected by internally or

39、 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 should also be taken to ensure that the testarea environment does not exceed the radio frequency orelectromagnetic interference capab

40、ilities 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 that will positively remove at least99.97 % of all particles of size equal to and greater than thatwhich the SPC will measure. Afte

41、r 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 consist of a SPC, selected onthe basis of its ability to count and size single particles in therequired size range. The SPC shall inclu

42、de 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 definition stated in ISO 14644-1(Table I of Federal Standard 209E), or from a different speci-fication of clean-area airborne parti

43、cle concentration at a statedminimum particle size. For classification levels based onmeasurement of particles larger than 0.05 m, an opticalparticle counter (OPC), an aerodynamic particle sizer or anequivalent SPC can be used. For classification levels based onparticles less than 0.05 m, a CNC in c

44、ombination 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 particle sensing/measurement chamber, an air flow meter-ing or control system, and an exhaust system. No abrupttransitions in dimension

45、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 characterization system. The sample inlet nozzleshould have a cross-sectional area equivalent to that of a circleof diameter at lea

46、st 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 flow 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 fl

47、ow 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. If a flexible transit tube is to be used, then noradius of curvature below 15 cm shall be used.7.1.2 Particle Sensing/Measureme

48、nt 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 parti

49、cle sensing occurs, thenthe SPC element that manipulates the particles shall not resultin significant particle number change during that process.7.1.3 Air Flow Metering of Control System, shall be locatedafter the particle sensing/measurement chamber so as tominimize particle losses or artifact generation before measure-ment occurs.7.1.4 Exhaust System, may consist of either a built-invacuum source or an external vacuum supply. If the built-invacuum source is used, then the exhaust stream from thatsource shall be suitably filtered so that particles samp