IEST G-CC1003-1999 Measurement of Airborne Macroparticles.pdf

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1、INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Contamination Control Division Technical Guide 103 IEST-G-C103 Measurement of Airborne acroparticles INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Arlington Place One 2340 S. Arlington Heights Road, Suite 10 Arlington Heights, IL 6005-4516 Phon

2、e: (847) 981-010 Fax: (847) 981-4130 E-mail: iestiest.org Web: ww.iest.org 2 Copyrighted material INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY IEST-G-C103 IEST-G-C103 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted material 3 This Guide is published by the INSTITUTE OF ENVIRONME

3、NTAL SCIENCES AND TECHNOLOGY to advance contamination con-trol technology and the technical and enginering sciences. Its use is entirely voluntary, and determination of its aplicability and suitability for any particular use is solely the responsibility of the user. Copyright 199 by the INSTITUTE OF

4、 ENVIRONMENTAL SCIENCES AND TECHNOLOGY ISBN 978-1-87862-76-2 No part of this publication may be copied or reproduced in any form, or by any means, including electronic, mechanical, photocopying, or otherwise, without the prior writen permision of the Institute of Environmental Sciences and Technol-o

5、gy, 2340 S. Arlington Heights Road, Arlington Heights, IL 6005-4516. INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Arlington Place One 2340 S. Arlington Heights Road, Suite 10 Arlington Heights, IL 6005-4516 Phone: (847) 981-010 Fax: (847) 981-4130 E-mail: iestiest.org Web: ww.iest.org 4 Copyri

6、ghted material IEST-G-CC1003 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGYIEST-G-CC1003 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted material 5Measurement of Airborne MacroparticlesIEST-G-CC1003CONTENTSSECTION1 Application 72 Scope 73 Sample handling procedures 84 Measurement

7、procedures 105 Procedure for determination of the M descriptor 126 Data reporting . 127 References 13APPENDIXAPPENDIX A; Data Report Example 14FIGUREFigure 1. Sampling probe inlet areas for isokinetic sampling . 8Figure 2. Vertical sampling probe inlet efficiencies in turbulent flow . 96 Copyrighted

8、 material IEST-G-CC1003 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGYIEST-G-CC1003 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted material 7INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGYContamination Control DivisionGuide 1003Measurement of Airborne MacroparticlesIEST-G-CC10

9、031 ApplicationThis guide describes procedures for measurementof the concentration and size of airbornemacroparticles (i.e., particles that are larger than 5m in diameter). The numerical value of the con-centration of such particles, expressed in terms ofmacroparticles per cubic meter, is the M desc

10、riptor.This term may refer to a specified concentration ofmacroparticles or to measurement of the concen-tration of macroparticles in a given sample of air.The procedures contained herein are suitable foruse in conjunction with related cleanroom stan-dards such as ISO 14644-1, for defining air clean

11、li-ness, and ISO 14644-2, for monitoring. The proce-dures are applicable to cleanrooms and clean zonesin any of three occupancy states, as defined in ISO14644-1.In relation to standard air cleanliness classifica-tions, as defined in ISO 14644-1, this document istypically most appropriate for use wit

12、h cleanroomand clean zone environments that qualify as ISOClass 5 or less clean. It may also be used in anysituation where process or product considerationsrequire monitoring or control of airborne contami-nants in the macroparticle size range.NOTE: For further definitions and explanations ofterms i

13、n this document, see IEST-RD-CC011.2 ScopeThere are numerous procedures available for count-ing macroparticles. Since different procedures maynot respond to the same particle size parameter(s),the data produced by a given procedure may notcorrelate with data from another procedure. There-fore, a var

14、iety of methods will be discussed herein.Two general categories of macroparticle mea-surement operations are considered:a) Collection by filtration or inertial effects, fol-lowed by microscopic measurement of the numberand size, or measurement of the mass of collectedparticles.b) In-situ measurement

15、 of the concentration andsize of macroparticles with a time-of-flight particlecounter or a discrete-particle counter.The importance of proper sample acquisitionand handling in order to minimize losses of macro-particles in the sample handling operations is em-phasized. Procedures are provided for ca

16、lculatingmacroparticle losses when ideal sample handlingprocedures cannot be accomplished.8 Copyrighted material IEST-G-CC1003 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGYNOTE: When the cleanliness of air is to be measuredas the air comes from a potential contaminatingsource, or as contaminate

17、d air approaches apotential target, an appropriate procedure shouldbe selected from ASTM F 50-00, reported, andfollowed.3 Sample handling procedures3.1 Sample acquisition3.1.1 Isokinetic samplingSampling of airborne macroparticles in unidirec-tional flow facilities or in ducts generally requiresisok

18、inetic sampling to minimize sampling losses.Isokinetic sampling is achieved when the samplingprobe inlet is faced into the direction from whichthe sampled airflow is approaching, with the probeaxis parallel to (isoaxial with) that flow, and whenthe mean flow velocity of the air entering the probeinl

19、et matches the mean flow velocity of the airbeing sampled at that location.Thin-walled sampling probes are recommended,with the ratio of the exterior diameter to the interiordiameter of the probe inlet face being 5 m, a low-power optical microscope capable of 100-fold mag-nification can be used. Pla

20、ce the membrane filterfrom the filter holder or aerosol monitor upon themicroscope stage. An observed field size should beselected which contains no more than 50 particles.Record the selected field size. Estimate the totalIEST-G-CC1003 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted m

21、aterial 11number of particles upon the membrane surface byexamining two fields. If the estimate is 500 or less,count all of the particles that are 5 m on thesurface of the membrane filter. If the estimate is500, count sufficient fields so that a total numberof 500 or more is counted.Determine the to

22、tal number of particles uponthe membrane filter by multiplying the number ofparticles counted by the ratio of membrane filtersurface to the area of the counted fields. Themacroparticle concentration is then defined as thetotal number on the membrane filter divided by thetotal airflow volume which pa

23、ssed through thefilter.4.1.2 Cascade impactor methodIn cascade impactors, the sampled airflow passesthrough a series of jets of decreasing orifice size.The larger particles are deposited directly belowthe largest orifices and smaller and smaller par-ticles are deposited at each successive stage of t

24、heimpactor.Two types of cascade impactors are used forcollection of macroparticles. In one, the particlesare deposited upon the surfaces of removable plateswhich are removed for subsequent weighing ormicroscopic examination. Sampling flow rates of0.00047 m3/sec or more are typically used for thistyp

25、e of cascade impactor. In the other type, theparticles are deposited upon piezoelectric quartzmicrobalance mass sensors which electronicallyweigh the particles collected by each impactor stage.This type of impactor uses significantly smallerflow rates.a) For the first type of cascade impactor, the i

26、nitialtare weight of each collection stage is recorded orthe tare number of particles per unit area is countedbefore any measurements are made. The impactoris placed at the selected sampling point locationand its outlet connected to a suitable vacuum source.The impactor is operated for a period of 1

27、0 minutesor more. At the end of that time, it is sealed andmoved to the microscope or balance facility. Thestages are removed.For each stage capable of collecting macro-particles, the number or weight of particles accu-mulated thereon is recorded. The tare values aresubtracted to determine the quant

28、ity collected dur-ing sampling.The macroparticle concentration is then definedas the total weight or number on the pertinentimpactor stages divided by the total airflow vol-ume which passed through the impactor.b) For the second type of cascade impactor, theparticle mass data are collected at the ti

29、me of sam-pling. Since the microbalance sensors for each stagecan be set to indicate the change in mass, it is notnecessary to determine initial tare weights beforesample collection begins.As with the other type of cascade impactor, thestages can be removed and measurements made ofindividual particl

30、es with a light microscope or par-ticle composition can be determined using an elec-tron microscope. This type of cascade impactor isreported to be capable of detecting concentrationsof 5 g/m3of airborne particles with specific grav-ity of 2. The sample flow rate is adjusted to 0.00039m3/sec and sam

31、ple duration set to time periodsfrom 10 minutes to several hours, depending uponthe clean area.The impactor is placed at the preselected sam-pling point location and turned on. At the end of thesampling period, the impactor can be moved toother locations and additional sample measure-ments can be ma

32、de.The macroparticle concentration is defined asthe total weight or number of particles on thepertinent impactor stages divided by the total air-flow volume which passed through the impactor.4.2 Counting procedures withoutparticle collectionMacroparticles can be measured without initiallycollecting

33、the particles from the air. The proceduresinvolve optical measurement of the particles sus-pended in the air. An air sample is moved at aspecific flow rate through a discrete-particle counterwhich reports either the equivalent optical diam-eter or the aerodynamic diameter of the particles.4.2.1 Disc

34、rete-particle counter methodThe procedures for macroparticle measurementusing a discrete-particle counter (DPC) are identi-cal to those specified in ASTM F 50 (reference 7c) forgeneral clean area airborne particle measurement,with one exception. The discrete-particle counterthat is used does not req

35、uire sensitivity for detec-tion of submicrometer particles since data are re-quired only for macroparticle counting.Care is required to ensure that the DPC samplesdirectly from the air at the sampling point location;sample lines to the DPC shall not be used. The DPCshould be capable of sample flow o

36、f 0.00047 m3/sec12 Copyrighted material IEST-G-CC1003 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGYand should be fitted with an inlet sized for isokineticsampling in unidirectional flow areas. In areaswhere nonunidirectional flow exists, the DPCshould be located with the sample inlet facingvert

37、ically upward. The sample inlet diameter is noless than 3 cm.The DPC size range settings are established sothat only macroparticles (particles 5 m) are re-ported. The data from one size range below the 5m point are recorded to ensure that the concentra-tion of particles smaller than macroparticle si

38、ze isnot so high as to cause coincidence error in the DPCmeasurement. The particle concentration in thatlower size range, when added to the macroparticleconcentration, shall not exceed 50% of the maxi-mum recommended particle concentration speci-fied for the DPC being used.4.2.2 Time-of-flight parti

39、cle countermethodMacroparticle dimensions can be measured with atime-of-flight instrument. An air sample is drawninto the instrument and accelerated to near-sonicvelocity by expansion through a nozzle into a par-tial vacuum, where a measurement region is lo-cated. Any particles in that air sample wi

40、ll acceler-ate to match the air velocity in the measurementregion. The particle acceleration time to match theair velocity will vary directly with particle massand inertia.Since the particle inertia is a direct function ofparticle mass, the relationship between the air ve-locity and the particle vel

41、ocity can be used to deter-mine the aerodynamic diameter of the particle.Knowing the pressure difference between that ofthe ambient air and the pressure at the measure-ment region, the air velocity can be calculateddirectly.The particle velocity is measured by the time offlight between two laser bea

42、ms. The differencebetween the particle velocity and the air velocity atthe measurement region will vary with the particleaerodynamic diameter. The time-of-flight instru-ment can measure aerodynamic diameters of par-ticles up to approximately 100 m with sizing reso-lution of 10% at rates of 10,000 pa

43、rticles/sec. The airsampling rate of this instrument is 0.0001 m3/sec.Sample acquisition procedures are the same asthose required when using a DPC to measuremacroparticles. In addition, the same proceduresfor the DPC are used with this instrument in estab-lishing the particle size ranges to be repor

44、ted.5 Procedure for determination ofthe M descriptorSet up the sampling inlet probe of the selectedinstrument at a specified sampling location. Samplethe required volume of air as agreed upon by thecustomer and the supplier or as specified for theparticular test method in use.If not otherwise specif

45、ied, the volume of air persample should be as follows:a) For installations operating at air cleanliness clas-sifications cleaner than ISO Class 5, the samplevolume should be at least 0.28 m3.b) For installations operating at ISO Class 5 andless clean, the sample volume should be at least0.028 m3.Rep

46、eat the procedure at all remaining samplingpoints. Their number and locations may be deter-mined in accordance with ISO 14644-1 or by agree-ment between the customer and the supplier.When the M descriptor data are collected for thepurpose of periodic testing of the cleanroom orclean zone, such as di

47、rected by ISO 14644-2, thenumber and locations of sampling points are se-lected and agreed upon by the customer and thesupplier. Special regard in the selection of locationsmay be placed on the positions of critical processes,equipment, and operations.Where information is required to determine thest

48、ability of concentrations of macroparticles, sev-eral (three or more) additional measurementsshould be made at selected locations over a speci-fied time interval, as agreed upon between thecustomer and the supplier.Calculate the M descriptor concentrations basedupon the defined macroparticle thresho

49、ld size(s),as agreed upon between the customer and thesupplier, and report the data as shown in section 6and Appendix A.6 Data reportingRecord the following information, as specified, foreach cleanroom or clean zone:a) Identification and location of the cleanroom orclean zone.b) Identification of the particle measuring instru-mentation and its calibration status, if applicable.c) Definition of the particle parameter to which theinstrument responds.IEST-G-CC1003 INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Copyrighted ma