1、Designation: F 2299 03Standard Test Method forDetermining the Initial Efficiency of Materials Used inMedical Face Masks to Penetration by Particulates UsingLatex Spheres1This standard is issued under the fixed designation F 2299; the number immediately following the designation indicates the year of
2、original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method establishes procedures for measuringthe i
3、nitial particle filtration efficiency of materials used inmedical facemasks using monodispersed aerosols.1.1.1 This test method utilizes light scattering particlecounting in the size range of 0.1 to 5.0 m and airflow testvelocities of 0.5 to 25 cm/s.1.2 The test procedure measures filtration efficie
4、ncy bycomparing the particle count in the feed stream (upstream) tothat in the filtrate (downstream).1.3 The values stated in SI units or in other units shall beregarded separately as standard. The values stated in eachsystem must be used independently of the other, withoutcombining values in any wa
5、y.1.4 The following precautionary caveat pertains only to thetest methods portion, Section 10, of this specification. Thisstandard does not purport to address all of the safety concerns,if any, associated with its use. It is the responsibility of the userof this standard to establish appropriate saf
6、ety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1356 Terminology Relating to Atmospheric Samplingand AnalysisD 1777 Method for Measuring Thickness of TextilesD 2905 Practice for Statements on Number of Speci
7、mensfor TextilesD 3776 Test Methods for Mass per Unit Area (Weight) ofWoven FabricE 691 Practice for Conducting an Interlaboratory Test toDetermine the Precision of Test MethodsF50 Practice for Continuous Sizing and Counting of Air-borne Particles in Dust-Controlled Areas Using Instru-ments Based Up
8、on Light-Scattering PrinciplesF 328 Practice for Determining Counting and Sizing Accu-racy of an Airborne Particle Counter Using Near-Monodispersed Spherical Particulate MaterialsF 778 Methods for Gas Flow Resistance Testing of Filtra-tion MediaF 1471 Test Method for Air Cleaning Performance of aHig
9、h-Efficiency Particulate Air-Filter SystemF 1494 Terminology Relating to Protective ClothingF 2053 Guide for Documenting the Results of AirborneParticle Penetration Testing of Protective Clothing Materi-als3. Terminology3.1 Definitions:3.1.1 aerosol, na suspension of a liquid or solid particlesin a
10、gas with the particles being in the colloidal size range.3.1.1.1 DiscussionIn this test method, aerosols includesolid particles having a diameter of 0.1 to 5 m suspended ordispersed in an airflow at concentrations of less than 102particles/cm3.3.1.2 isokinetic sampling, na condition where the veloci
11、tyof the airflow entering the sampling nozzle is the same as thevelocity of the airflow passing around the sampling nozzle.3.1.3 monodispersion, nscattering of discrete particles inan airflow where the size is centralized about a specific particlesize.3.1.3.1 DiscussionIn this test method, the monod
12、ispersedparticle distribution has a mean diameter size of the aerosol inthe 0.1 to 5 m range, with a coefficient of variation of themean diameter of 610 % or less, as certified by the manufac-turer.1This test method is under the jurisdiction of ASTM Committee F23 onProtective Clothing and is the dir
13、ect responsibility of Subcommittee F23.40 onBiological Hazards.Current edition approved July 10, 2003. Published September 2003.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informatio
14、n, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 For definitions of other protective clothing-related termsused in this test method, refer to Terminology F 1494.4.
15、 Summary of Test Method4.1 Filtered and dried air is passed through an atomizer toproduce an aerosol containing suspended latex spheres.4.1.1 This aerosol is then passed through a charge neutral-izer.4.1.2 The aerosol is then mixed and diluted with additionalpreconditioned air to produce a stable, n
16、eutralized, and driedaerosol of latex spheres to be used in the efficiency test.5. Significance and Use5.1 This test method measures the initial filtration efficiencyof materials used in medical face masks by sampling represen-tative volumes of the upstream and downstream latex aerosolconcentrations
17、 in a controlled airflow chamber.5.2 This test method provides specific test techniques forboth manufacturers and users to evaluate materials whenexposed to aerosol particle sizes between 0.1 and 5.0 m.5.2.1 This test method establishes a basis of efficiencycomparison between medical face mask mater
18、ials.5.2.2 This test method does not establish a comprehensivecharacterization of the medical face mask material for aspecific protective application.5.3 This test method does not assess the overall effective-ness of medical face masks in preventing the inward leakage ofharmful particles.5.3.1 The d
19、esign of the medical face mask and the integrityof the seal of the medical face mask to the wearers face are notevaluated in this test.5.4 This test method is not suitable for evaluating materialsused in protective clothing for determining their effectivenessagainst particulate hazards.5.4.1 In gene
20、ral, clothing design is a significant factor,which must be considered in addition to the penetration ofpenetration of particulates.6. Apparatus6.1 The aerosol test system incorporates the components asshown in Fig. 1. A more detailed diagram of test systemcomponents and equipment is found in STP 975
21、.36.2 Equipment:6.2.1 Clean, dry compressed air supply,6.2.2 HEPA filters (2),6.2.3 Aerosol generator,6.2.4 Charge neutralizer,6.2.5 Humidifier,6.2.6 Test filter holder and duct assembly,6.2.7 Pressure drop measuring device,6.2.8 Air flow rate measuring device,6.2.9 Temperature and relative humidity
22、 detectors,6.2.10 Air blower (optional for negative pressure system),and6.2.11 Optical particle counters.7. System Preparation and Control7.1 To test in the aerosol particle size range of 0.1 to 5.0 m,it is necessary to maintain a very clean inlet air supply.Achieveacceptable levels of background ae
23、rosol by passing the atom-izing air supply sequentially through a silica-gel dryer (forreduction of moisture), a molecular sieve material (for removalof oil vapor) and an ultra low penetrating aerosol (better than99.9999 % efficient at 0.6 m) filter. Then, supply the air to thetest chamber of aeroso
24、l generator through pressure regulatorsof 67 kPa 61 psi accuracy. For throttling of the main airflowas well as other flow splitting requirements, use needle valvesto maintain adequate flow stability and back pressure. Forrecommended flow control measurement, see 7.6. Monitor andrecord the temperatur
25、e and relative humidity at the exhaust portof the test chamber. To avoid interference from the test aerosol,take the humidity measurement from the outlet side of theHEPA filter (see 7.6.2) with an in-line probe.7.1.1 To provide a stable, reproducible aerosol through thetest material that remains con
26、stant over the sampling time ofthe efficiency test, maintain the main test duct and filtermedium specimen holder in a vertical orientation to minimizeaerosol sedimentation losses.7.2 Aerosol Generation:7.2.1 The aerosol generator must be capable of a latexsphere count concentrations output of 107to
27、108particles/m3.The suspension reservoir must be large enough to sustain astabilized output greater than 1 h. Two commercially availableatomizing techniques that provide these concentrations of thelatex spheres are presented in Figs. 2 and 3.7.2.2 As viewed in Figs. 2 and 3, these techniques utilize
28、 theatomizing of suspended uniform latex spheres from dilutewater suspensions. One liter quantities of these suspensionscan be made by diluting the 10 % by volume solids of theuniform latex spheres at 1000 to 1 or greater dilution ratios indeionized, filtered distilled water.NOTE 1The suspensions ha
29、vea3to6month usable life. Idealsuspension dilutions are a function of the latex particle size to the aerosolgenerator droplet size. In order to minimize the atomization of doublets orhigher aerosol multiples in the drying process, a recommended latexsuspension dilution ratio has been established so
30、that dilution ratios are onthe order of 1000:1 to 10 000:1.4Other aerosols produced from theseatomizers can be classified into monodispersed systems but for anindustrially recognized standard of particle size and composition theuniform latex spheres are the most reproducible and readily availablepar
31、ticles.7.3 Aerosol NeutralizerThis procedure recommends theuse of an aerosol charge neutralizer at the inlet of the testsystem. This technique generally will ensure aerosol surfacecharge stability. The aerosol neutralizer can be in the form of aradioactive decay ionizer. The desired Boltzmanns charg
32、eequilibrium for the aerosol has been described.5Typically, anionizing flux of 103mCi/m3/s provides the required aerosolneutralization.3Symposium on Gas and Liquid Filtration, ASTM STP 975, ASTM, Vol 11,1986, pp. 141-164.4Raabe, O., “The Dilution of Monodispersed Suspensions for Aerosolization,”Amer
33、ican Industrial Hygiene Association Journal, Vol 29, 1968, pp. 439-443.5Liu, B. Y. H. and Piu, D. Y. H., “Electrical Neutralization ofAerosols,” AerosolScience, Vol 5, 1974, pp. 465-472.F2299032NOTE 2A Krypton 85 source, a Polonium 210 source, or a Coronaelectrical discharge, A-C source have been fo
34、und satisfactory for thispurpose.7.4 Aerosol Dilution and Humidity ControlPrior to injec-tion or dispersion of the initial aerosol concentration into themain test chamber, dry or dilute the aerosol with make-upairflow for the final test aerosol concentration as needed.Conduct material testing in a r
35、elative humidity range of 30 to50 % and hold the relative humidity 65 % during a given test.FIG. 1 Schematic of Test MethodF2299033Complete the aerosol mixing a minimum of 8 duct diametersdistance before the inlet sampling probe and the materialspecimen.7.5 Material Specimen Holder:7.5.1 The materia
36、l specimen holder and test section shall bea continuous straight walled vessel, interrupted only by thefilter medium sample throughout its length. The materialspecimen holder must provide an uninterrupted airflow, pas-sage without measurable peripheral air leakage. Use a 50 to150 mm 2 to 6 in. cross
37、-sectional diameter for the mediumsample size. Choose the specimen size to ensure that the testspecimen is representative of the overall material and providesenough rigidity to be self-supporting.NOTE 3The recommended filter medium cross sections allow facevelocities of 0.5 to 25 cm/s approximately
38、1 to 50 ft/min at flow rates of1 L/min to 1 m3/min approximately 0.035 to 35 ft3/min to be developedin testing.7.5.2 Introduce the latex aerosol a minimum of 10 ductdiameters upstream of the material specimen and at a sufficientdistance to provide thorough mixing before the upstreamsampling probe.7.
39、6 Airflow Metering:7.6.1 Use a positive pressure (compressed air) or a negativepressure (exhaust fan or blower) system for the airflow to themain test chamber. For the application of any of thesetechniques of airflow measurement and calibration, refer to thestandards and practices of theAmerican Soc
40、iety of MechanicalEngineers.7.6.2 Use a High Efficiency Particulate Aerosol (HEPA)type filter (99.97 % efficiency on 0.3 m aerosol) upstream ofthe systems airflow measurement. Size the HEPA type filter toprovide adequate system collection of the exhausting testaerosol.7.7 Pressure Drop Measurement:7
41、.7.1 Use static pressure taps that are flush with the ductwalls at a distance of 1 duct diameter upstream and down-stream of the filter medium faces.7.7.2 With no filter medium in the sample holder, there shallbe no measurable pressure loss between the inlet-side andoutlet-side pressure taps. Use a
42、pressure-measuring instrumentcapable of being read to 60.025 cm of water gauge to makethis determination.7.8 Aerosol Sample Extraction and TransportUse geo-metrically and kinematically identical centerline probes toextract representative aerosols from the inlet and outlet sides ofthe material specim
43、en test section. Use probes that have aradius of curvature (R)of12cmorR/D (Diameter) 20:1 andpresent a cross-sectional area of less than 10 % of the cross-sectional area of the test system ducting. Locate the upstreamFIG. 2 AtomizerFIG. 3 Collision AtomizerF2299034probe 8 duct diameters (minimum) do
44、wnstream of the aerosolinjection point and 2 duct diameters ahead of the materialspecimen. Locate the downstream probe 3 duct diametersdownstream of the filter medium specimen. To minimizeaerosol sampling transport line losses due to settling, diffusionand inertia for the aerosol particle size range
45、 of the test method,use the following characteristics of the sampling.7.8.1 Maintain the sampling line flow in the laminar flowregime; that is, the Reynolds Number must be less than 1000.Calculate the Reynolds Number in accordance with the follow-ing formula:Re# 5rgVD1g(1)where:rg= gas density (kg/m
46、3),V = gas velocity (m/s),D1= inside diameter of sampling lines (m), andg= gas viscosity (kg/m-s).7.8.2 Limit horizontal sampling line length to less than 100cm and the total sample transport line to less than 2 m.7.8.3 Maintain all radius of curvatures to greater than 12cm.NOTE 4Isokinetic aerosol
47、sampling is recommended to minimizeprobe inlet losses. However, in those cases where isokinetic conditionscannot be met, it is recommended that the operation of these probes be610 % of isokinetic or that the particle Stokes Number at the probe inletbe held to less than 1.0 in order to minimize inert
48、ial losses at the probeinlet. It is also recommended that the Reynolds Number of the sampleflow lines be held to less than 2000. The Stokes Number is calculatedusing the following formula:St# 5Dp2rpVC9gDn(2)where:Dp= particle diameter (m),rp= particle density (kg/m),V = velocity of approach (m/s),g=
49、 gas viscosity (kg/m - s),Dn= diameter of sampling nozzle (m), andC = Cunningham correction factor, which for particleslarger than 1.0 3 10-6m (1 m) is assumed to be 1.0.NOTE 5Recommended sampling flow rates for extraction of themounting volume are to be less than 10 % of the total test system flowrate.7.9 Aerosol Concentration Counting:7.9.1 This practice is structured for utilizing automatic,single particle light-scattering counters. For an illustration ofthe application, calibration, and analyses by these instruments,refer to Practices F50and F 32
