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Aerosol Photometers: The Gold Standard in HEPA Filtration Testing Presented by: Dave Crosby Tim McDiarmid Don Largent Air Techniques International www.ATItest.com.

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Presentation on theme: "Aerosol Photometers: The Gold Standard in HEPA Filtration Testing Presented by: Dave Crosby Tim McDiarmid Don Largent Air Techniques International www.ATItest.com."— Presentation transcript:

1 Aerosol Photometers: The Gold Standard in HEPA Filtration Testing Presented by: Dave Crosby Tim McDiarmid Don Largent Air Techniques International

2 Introductions

3 Agenda History of Photometry Science of Photometry Applications of Photometry

4 History of Photometers & HEPA Filters

5 “You can’t have one without the other”

6 The photometer was first since there was a need David Sinclair, Ph.D. (Nephelometer) (Not portable and had logarithmic display)

7 Air Pollution Research 1933

8 WW II generated a high priority need It all started in 1942

9 Some Key Players Wendell Anderson, Humphrey Gilbert, Dr. Melvin First

10 Captured WW II German Gas Masks The US had performed no gas mask development since WW 1 German masks used cellulose asbestos media patented by Dräger Werke in 1933 Wendell Anderson working with H&V developed media comparable to the German sample

11 M10A1 Canister

12 Tank & APC M-25 Mask

13 Smoke Penetrometer to test the gas mask paper & filters

14 First Linear Photometer

15 Space Filter US military needed filtration of room areas for people and used gas mask media for a pleated filter for larger air flow ( ) Know as “Collective Protection” Used cardboard spacers between pleats, which had high air flow resistance

16 Cardboard Pleat

17 Manhattan Project Humphrey Gilbert safety engineer at Los Alamos was sent to Oak Ridge Filters used in Manhattan Project were very thick with extremely high pressure drop Foresaw need for high efficiency air filters in HVAC systems

18 Absolute Air Filter Gilbert (now with AEC) unhappy with Army Space filter and its limitations AEC in 1948 gives Author D. Little a contract to redesign filter and find a supplier Walter Smith Ph.D. comes up with corrugated cardboard separator idea

19 Improved Pleated Filter Design

20

21 HEPA Filter Development First Air Cleaning Seminar for AEC personnel held June 1951 at Harvard Air Cleaning Laboratory First Handbook on Air Cleaning distributed at meeting Fires at several weapons plants made need for high temperature and water resistance necessary

22 Second Air Cleaning Conference held in Ames, IA 1952 Melvin W. First Ph.D. Presented four research papers

23 Military develops procedures and Apparatus to test High Efficiency filters and related products Penetrometers Q-127 Low Flow Q-76 Med. Flow Q-107 High Flow Rough Handling Water Repellency etc.

24 HEPA Development for Fire & Water Resistance (1953)

25 First HEPA Guide (1961)

26 Willis Whitfield (1961) Discovery of Laminar Flow at Sandia National Labs

27 SNL Demonstrates Clean Room Concept in Chicago for IES(T) (1962)

28 First “In Place Filter Test”

29 First Portable Linear Photometer TDA-2 (1962)

30 JM-1000 Photometer (1964)

31 Next Portable Photometer TDA-2A (1964) First Scanning Probe Cabinet covered in white Formica (White Rooms)

32 Next Portable Photometer TDA-2B ( ) Ergonomic front panel design

33 First Commercial Standards (1967)

34

35 Discussion

36 What is a Filter

37 Before Photometry… What is a Filter? –Filtration Mechanics –MPPS How to Test a Filter –Efficiency –Leak (Integrity)

38 What is a Filter? Separation of one phase from another Solids or liquids in Air (Home Furnace) Solids in liquid (Auto Oil/Gas) Liquid in Air (Air oil separators) Liquid in liquid (RO) Gas in Gas (Activated Carbon)

39 What is a Filter? A Controlled Leak! Filtration controls the amount of impurity that is allowed to pass. There is no such thing as a ‘perfect’ filter (no resistance and 100% efficiency)

40 Filtration Types Materials –Fibers –Fibrous Structures –Micropores Performance –High Efficiency –Low Efficiency

41 What are we dealing with? Solids or liquids in Air & Fibrous Filters Other structures are more common in ultra filtration and special applications

42 Fibrous Filters Typically Depth Filters –Filtration throughout media depth –Very low to very high particle removal Fibrous Filter Construction –Filter Disks/Pads –Pleated Cartridges –Bags/Pockets

43 Filtration Mechanics Pressure Drop Single Filter Efficiency Collection Mechanisms

44 Darcy’s Law ΔP

45 Darcy’s Law

46 Filter Pressure Drop Pressure Drop Linear Pressure DropInertialVelocity (Darcy Law) RegimeRegime CLEANROOM HVAC

47 Filtration Assumptions Fibers are in cross flow Particles are ‘collected’ upon contact with fiber Uniform fiber diameter Uniform particle size

48 Single Fiber Efficiency η s = Particles collected by fiber. Particles in volume of air geometrically swept out by fiber Air Volume swept out by fiber

49 Fiber Structure - HEPA

50 Particle Collection Mechanics Sieving Inertial Impaction Diffusion Interception

51 Particle Collection: Sieving Fibers Particle Flow

52 Particle Collection: Interception

53 Particle Collection: Inertial Impaction

54 Particle Collection: Diffusion

55 Particle Collection Mechanisms

56 High Efficiency Filter MPPS (Most Penetrating Particle Size) Particle Size Penetration MPPS 0.08 to 0.18µm Impaction Diffusion

57 Filtration is Selective Particle Collection Small and big particles are more effectively collected

58 Impact of Flow Rate on Efficiency

59 A Filter’s Performance is Determined at Media Velocity Media Velocity Face Velocity Media Velocity is Lower Than Face Velocity

60 Consideration in Filter Design Penetration or efficiency Critical Particle Size Pressure Drop or resistance (Cost)

61 Filter Tests Efficiency –Media Manufacturer –Filter Manufacturer –3 rd Party Certification Leak/Integrity –Filter Manufacturer –Field/In-Situ

62 Efficiency Testing Challenge filter with aerosol at or near the MPPS –This requires a mono-dispersed aerosol (tight distribution) Measure upstream and downstream concentration Sequential or parallel (simultaneous) measurements Efficiency = 1 – Downstream Upstream Note: This is a ‘global’ measurement (i.e. entire filter)

63 Typical Filter Efficiency Test System Recommended filter performance test system from IEST RP-CC-0021

64 What is a Leak? Leak is a local measurement. Leak is generally 5 –10 times the average penetration at a local spot. Therefore we do not require a mono- dispersed challenge aerosol at the MPPS –Easier and less costly to generate larger particles with a broader distribution.

65 A Good Filter Will Allow Few Particles to Penetrate o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o 0 o

66 Add a Leak and… o o o o o o o o o o o o o o o o o o o o o o o o o o o o 00 o o o o o 0 0 O o o o o o o 0 0o o o

67 Test for a Leak/Integrity Measure local penetration at each sample location to determine: –Filters are not faulty / not been damaged –Filters have been installed properly –There are no leaks in the mounting frame / between mounting frame and housing –System contains no by-pass of the filter

68 Leak/Integrity Scanning Ensure that all parts of filter are within specification

69 Efficiency vs. Leak/Integrity in General Terms Efficiency Testing Leak Testing GlobalLocal Determine % Penetration Yes Yes 1 Pinpoint LeaksNo Yes Manufacturer Test YesYes 2 Field TestNo Yes 1 – Local % penetration, not overall efficiency 2 – Due to variations in the media manufacturing process

70 Discussion

71 When Testing a Filter What are We Looking For?

72 Let’s Review… Particulate penetration as –Efficiency –Leak Size of interest? –MPPS from 0.08 to 0.18 micron –Even when looking for a leak? However…..

73 What is a particle?

74 The Simplest Particle?

75 Equivalent Particle Size Diameter of a Sphere that has the same magnitude of a chosen Property as the particle In question –Optical Diameter (Eye/microscope) –Scattering Diameter (Light Scattering) –Electric Mobility (Charge On Particle) –Mobility (Diffusion) –Stokes Diameter (Drag Forces) –Aerodynamic Diameter (Settling Speed)

76 In Filtration, Collections of Particles Interest Us AerosolSolid/Liquid and Gas (dust, fog) HydrosolSolid/Liquid and Liquid (milk, paint, lotion) FoamGas in Solid or Liquid (sponge, shampoo)

77 Key Concepts Drag Force – proportional d p > 10µm Slip Correction for d p < 10µm Stopping Distance and Relaxation Time Settling velocity Mobility and Electric Mobility Diffusion and Brownian Motion Coagulation Dimensionless Numbers

78 Units of Measurement in Filtration µmMicrometer, meter NmNanometer, meter AAngstrom Unit, meter 1 µm = 1,000 nm = 10,000 A Some perspective: 1cm is 1000 µm 1in = 2.54 cm = 25,400 µm

79 ItemApproximate Particle Diameter Eye of a Needle1,230 microns Beach Sand100 – 2000 microns Table salt~100 microns Human hair microns Talcum powder~10 microns Tobacco Smoke0.01 – 1.0 microns Bacteria microns Virus<0.005 – 0.05 microns Particle Sizes of Interest

80 Typical Particle Sizes 0.3um

81 Another Particle Size Chart

82 Typical Settling Velocity Diameter (um)Feet/min

83 How is an Aerosol Characterized? Frequency X (range)Raw DataNormalized 0 to to to Consider this data set

84 Normalized Frequency Distribution Y/ΔX

85 Size Distribution Terms Independent variable, X Mean X m Standard Deviation, σ Mode (peak) Median (50 th percentile)

86 Arithmetic Standard Deviation

87 Geometric Standard Deviation

88 Particle Size Distribution Most Natural Processes are Geometrically Distributed and often multi modal Number (count), Surface, or Volume (mass) Distribution are common weightings

89 Why is this important? Due to data weighting… …the 0.3um DOP particle measured in the 50’s is a volume (mass) mean… …whose number (count) median is actually closer to 0.18um…the MPPS

90 Geometric vs. Arithmetic Consider Geometric as Arithmetic or Linear on a log scale Geometric spreads out the lower end In Arithmetic, equal differences result in equal spacing In Geometric, equal ratios result in equal spacing

91 Geometric vs. Arithmetic Equal intervals Arithmetic: = = … (equal differences) Geometric: 10/7.48 = 7.48/5.62 = … (equal ratios)

92 Why Use Log Normal Distributions? No Negative Values For known distributions, the Means of different weightings can be calculated from the others For example, Mass (volume) Mean calculated from Count (number) mean

93 Number and Volume Weighting dpdp Number CountsVolume (πd 3 /6) 11,000,000523, , ,000

94 Key Points to Remember Particles come in many shapes and sizes ALL measurements determine some physical property and provide an Equivalent Size In filtration, larger particles settle out and are not important, particularly cleanrooms Geometric Distributions (aka Log Normal) are used to define particle size distributions Mass and Number weightings are common in particle measurements

95 Discussion

96 Now we know we are looking for particles… The Light-Particle Interaction

97 Primary Light-Particle Interactions Elastic Scattering –Rayleigh Scattering –MIE Scattering –Phase Shift –Polarization Absorbtion

98 Incident Light LIGHT PARTICLE INTERACTION Diffraction Reflection Raman Fluorescence Refraction Emission Absorption Scattering

99 Common Properties Refraction – the apparent change in direction of light due to change in refractive index within one medium or between dissimilar medium Reflection – redirection of light at the surface of a material Diffraction – bending or deflection of light around a particle Polarization – oscillations of the light occurring in a defined plane

100 Complex Numbers (4) 1/2 = 2 What is (-1) 1/2 ? It is defined by the symbol i A complex number is written as (a - b i ) where the imaginary part is represented by the symbol i

101 Refractive Index Refractive Index of a material is a complex number Usually given as i The imaginary part is due to absorption

102 Refractive Index of Common Materials Quartz i Glass1.5 to i PSL i Ca Sulfate i Carbon2.0 – 0.33 i Iron1.5 – 1.63 i

103 Refraction Refractive Index = sine r / sine i i r

104 Size and Scattering Regimes Size Range of Interest

105 Elastic Scattering Redirection of Incident Light without change in wavelength Refraction – internal to particle, wavelength and composition dependent Reflection – at surface of particle, dependent on wavelength and composition Diffraction – external to particle, independent of wavelength and composition

106 Particle Size Affects Elastic Scattering Optical Particle Size (α) α = πd / λ where: d = particle diameter λ = wavelength Scattering Intensity (I s ) I s = λ 2 f(α) where: f(α) is a size dependent function

107 Light Scattering Particles much smaller (< 0.025um) than the wavelength of light results in Rayleigh Scattering Particles comparable to the wavelength of light (0.025> x < 2.5um) results in MIE Scattering Much larger particles result in geometric scattering.

108 Light Scattering Particles much smaller (< 0.025um) than the wavelength of light results in Rayleigh Scattering Particles comparable to the wavelength of light (0.025> x < 2.5um) results in MIE Scattering Much larger particles result in geometric scattering.

109 Rayleigh Scattering

110

111 Mie Scattering Wavelength, λ Incident light

112 MIE Scattering

113

114 Discussion

115 Multiple and Single Particle Sensing and Sensors

116 Multiple Particle Sensing Sampling Volume ≥ 1/number concentration Independent of sample volume (measuring a ‘cloud’) Precision depends on averaging time (due to variations in the ‘cloud’)

117 Multiple Particle Sensors Extinction (umbrella) –Smoke Meter (soot content in exhaust stack) –Transmissometer (visual ranging) Scattering –Intensity (nephelometry) –Backscatter (LIDAR) –Photometry

118 Photometer Aerosol is illuminated by a light source Total scattered light is detected by PMT Total concentration is measured

119 Photometer Aerosol Light Source Focus Optics Collector Optics Photodetector Electronics

120 Photometer Focal Point

121 Nephelometer Particle density is a function of the light reflected into the detector from the illuminated particles

122 Multiple Particle Sensors Summary Light-Particle interaction results in scattering Optical instruments in particle measurement is dependent upon the particle size and scattering properties Multiple particle scattering is independent of volume; depends on averaging time.

123 Single Particle Sensing Sample Volume << 1/number concentration Requires a precise, known volume of sampled air Same as counting events; precision depends on total counts

124 Single Particle Sensors Light attenuation (extinction) Scattering (Particle Counters) –Laser –White Light Angular Scattering Doppler anemometer

125 Particle Counter O O Electronics Light Source Focus Optics Collector Optics Photodetector

126 Common Particle Counter Challenges Multi Valued Response Coincidence Problems at small particle sizes

127 Multi Valued Signal

128 Coincidence O O Electronics Light Source Focus Optics Collector Optics Photodetector

129 Small Particle Detection Scattering intensity is very small Common Solutions –Increase intensity of light –Change light source wavelength –New techniques?

130 Small Particle Detection Increase Intensity –Improves signal from particles –Increases noise from air molecules Reduce the wavelength –Shifts the curves to smaller sizes –Increases noise from molecules Reduce the viewing volume

131 Saturator Vapor Condensation Nucleus Counter Aerosol Alcohol Condensation Nucleii

132 Single Particle Sensors Summary Most optical measurements are in the MIE regime Single particle counting requires known volume of sampled air Same as counting events; precision depends on total counts – long sample times at low counts Problems of coincidence at high concentrations Non unique response and low signal to noise ratio at small sizes Small sizes handled by using smaller wavelengths or proprietary methods

133 Photometer vs. Particle Counter vs. CNC Photometer –Measures Total Aerosol –Response Linear With Total Aerosol Volume –Requires Known Aerosol And Relatively High Concentration –Problems: No Particle Size Information Requires High Concentrations

134 Particle Counter (Laser) –Detects and sizes particles –Counts by size –Measures down to 0.1 μm –Can use any aerosol –Problems: Assumes everything measured is a PSL Multi Valued Response Coincidence Problems at small particle sizes Long sample times to obtain a statistically valid results Photometer vs. Particle Counter vs. CNC

135 CNC –Particle detector only –Can measure less than 0.05 μm –Problems: Requires mono-dispersed aerosol Counts all particles, noise at bottom end Long sample times to obtain a statistically valid results Photometer vs. Particle Counter vs. CNC

136 Discussion

137 Aerosols and Aerosol Generators

138 What is a Standard? A KNOWN and Universally Accepted value of a physical property or quantity –Meter for measure of length – ◦ C for Temperature

139 Why are Standards Necessary? They establish accuracy of measuring instruments Calibrate the accuracy of instruments in use –Temperature –Scales –Flow Meters –Photometers –Particle Counters

140 How Does this Affect Aerosols? A Standard Aerosol has KNOWN properties –Particle Size and Distribution –Concentration –Shape (usually spherical) –Chemistry (inert) –And Refractive Index in our business

141 Aerosol Standards Mono-disperse Aerosol –‘Single’ size particles σ g ≤ 1.4 Instrument Calibration for PCs Research & Development Near Mono-disperse Aerosol –Narrow distribution 1.4 < σ g ≤ 1.6 Some Production QC Level of accuracy Poly-disperse Aerosol –Broad distribution 1.6 < σ g –Industrial measurements –Instrument verification –Some instrument calibrations

142 Mono vs Poly Disperse

143

144 Implication on Size Dispersion For a log normal distribution –95% of the particles are between Meanσ g 2 σ g 2 & Mean

145 Implication on Size Dispersion An aerosol with mean of 0.3um – σ g = % of particles are between 0.21 & 0.43um – σ g = % of particles are between and 1.2um

146 Mono vs Poly Disperse

147 Three Types of Aerosol Mono-disperse: σ g ≤ 1.4 Near Mono-disperse: 1.4 < σ g ≤ 1.6 Poly-disperse: 1.6 < σ g

148 Typical Poly-Disperse Aerosol Standards Laskin Nozzle Wright Nebulizer Pneumatic Nebulizer Condensation Generators Spinning Disk Exploding Wire Standard Dusts

149 Laskin Nozzle Air Entrained Liquid Aerosol

150 Laskin Nozzle

151

152 Laskin Nozzle Concentration Calculations Output of Laskin Nozzle is defined: By # 20 PSIG Concentration = # Nozzles x 13,500 Total Flow (cfm) By # Jets at 20 PSIG Concentration = # Nozzles x 3,375 Total Flow (cfm) *Note: there are 4 jets in a standard Laskin Nozzle

153 Laskin Nozzle Concentration Calculations You can calculate the system concentration, if you know: –System Air Volume (CFM) –Number of Laskin Nozzles/Jets at 20 PSIG You can calculate the number of nozzles/Jets, if you know: –System Air Volume (CFM) –Desired system concentration

154 Wright Nebulizer

155 Pneumatic Nebulizer Liquid Aerosol Compressed Air

156 Thermal Condensation Aerosol Generators Heater O 0 O o 0 Quench Air Vapor Aerosol Liquid Compressed Gas Quench Air

157 Thermal Aerosol Generator Polydispersed Produces a greater level of aerosol concentration than pneumatic type nozzle Applications include higher flow systems Median particle size is smaller than pneumatic generation Output concentration cannot be calculated as output is variable Size and distribution shift with concentration

158 Ultrasonic Nebulizer

159 Spinning Disk Particle Generator

160 Exploding Wire

161 Test Dusts Standard Dust (Arizona Road Dust) –Mainly Silica with Mass Mean Diameter of 7 µm σ g of 3.6 Specific Gravity of 2.7 –Originally collected from Arizona Desert

162 Test Dusts ASHRAE –Custom blend of: 72% ISO , A2 Fine Test Dust, 23% powdered carbon 5% milled cotton linters –Attempt to simulate natural dust for HVAC

163 Test Dusts SAE Dusts – automotive filter testing –Fine Mass Median Diameter ~ 25µm No particles > 100µm –Coarse Mass Median Diameter ~ 60µm 10%+ may be larger than 100µm

164 Common Mono-disperse Aerosol Standards Poly Styrene Latex (PSL) Vibrating Orifice Electrostatic Classification Condensation Techniques

165 PSL Aerosols NIST Traceable PSL Particles –Examples –Methodology Atomize PSL in Liquid (water) Evaporate the liquid NIST Traceable PSL Aerosol

166 PSL Aerosols

167 Residue & PSL Aerosols Impurities in water become small particles These particles can be counted as particles in standard aerosol, especially by a CNC

168 Residue & PSL Aerosols Assuming a typical 2um atomizer droplet and 10 ppm purity water, Residue particle size can be computed 10 x = (residue dia/drop dia) 3 Residue Diameter = 0.04um

169 Residue Particles

170 PSL Aerosols Common for Cleanroom Applications NIST traceable PSLs are expensive PSLs are easy to aerosolize, but output concentration is variable Limited by residue at small sizes Not available in large sizes PSL gives excellent optical response Used as calibration aerosol for particle counters

171 Electric Mobility Classification

172 Points to Remember Standards are required to verify and calibrate instruments and devices A Standard aerosol can be either poly or mono disperse R&D standards are more precise and are for laboratory use Industrial standards are easier to produce and are widely used

173 Points to Remember cont’d. Poly-disperse aerosols are commonly generated by atomization, nebulization or mechanical means Only a few techniques are available to generate very tight, mono-disperse aerosols NIST traceable PSLs are generated in small quantities and are very expensive PSL concentration output is variable Residue particles can be a problem in small sizes

174 Discussion

175 Photometer Testing Standards & Practices

176 What is a “Filter” Testing Standard? A DOCUMENTED and Universally Accepted method of obtaining a Qualitative Performance Measurement

177 Why are Standards Necessary? They establish consistent methodology Provide a guide for understanding and compensating for variables encountered during practical application

178 How Does this Affect Filter Testing? A Test Standard defines methods and limits –Aerosol characteristics –System Operating Conditions –Testing protocols Allowable Challenge Concentrations Sampling Rate Maximum “Allowable” Leakage Scanning Speed

179 Standards & Recommended Practices Organizations AACC (American Association for Contamination Control) ISO (International Organization for Standardization) BNL (Brookhaven National Laboratory) ASTM (American Society for Testing and Materials) EN (European Norm) IEST (Institute of Environmental Science & Technology) ANSI (American National Standards Institute) ASME (American Society of Mechanical Engineers) DOE (Department of Energy)

180 Filter Testing Standards CS-IT (1968) Standard for HEPA filters CS-2T (1968) Standard for Laminar Flow Clean Air Devices - Installation Leak Test (filter and gaskets) CS-2T (1968) Standard for Laminar Flow Clean Air Devices - Induction Leak Test (seams and joints) (2005) Cleanrooms & Associated Environments, Annex B- Test Methods (Informative) IH62300 (2001) In-Place HEPA Filter testing, Section 6.2 Equipment EN High Efficiency Air Filters (HEPA & ULPA)-Part 2: Aerosol Production, Measuring Equipment, Particle Counting Statistics IES-RP-CC001 HEPA & ULPA Filters IES-RP-CC006 Testing Cleanrooms IES-RP-CC007 Testing ULPA Filters IES-RP-CC034 HEPA & ULPA Filter Leak Tests Fed Std 209E (1992 by IEST) Most referenced in “Filter” industry was replaced by ISO & 2 in November 2001 NSF 49:2008 (Annex A:2008) Biosafety Cabinetry: Design, Construction, Performance & Field Certification-Performance Tests NSF 49:2008 (Annex F:2008) Biosafety Cabinetry: Design, Construction, Performance & Field Certification-Field Tests ASME N509 (2008) Nuclear Power Plant Air-Cleaning Units & Components) N510 (2007) Testing of Nuclear Air Treatment Systems N511 (2007) In-Service Testing of Nuclear Air Treatment Heating, Ventilating and Air-Conditioning Systems DOE-HDBK-1169, DOE Handbook Nuclear Air Cleaning Handbook, Section In-Place Testing

181 Industries Using Photometry Pharmaceutical Non-pharmaceutical –Civilian Nuclear Power –Military Nuclear Weapons Chemical Weapons Biological Weapons

182 Photometer vs. Discrete Particle Counter 1968 CS-1T Standard for HEPA Filters Photometer Upstream challenge aerosol must be at least 27ug/l Maximum Leakage = 0.01% Scanning rate = 2 inches per 1 inch from filter face Particle Counter No defined method

183 Photometer vs. Discrete Particle Counter 1968 CS-2T Standard for Laminar Flow Clean Air Devices –Installation Leak Test (for filter & gaskets) Photometer Upstream challenge aerosol must be at least 27ug/l Maximum Leakage = 0.01% Scanning rate = 2 inches per 1 inch from filter face Particle Counter No defined method

184 Photometer vs. Discrete Particle Counter 1968 CS-2T Standard for Laminar Flow Clean Air Devices –Induction Leak Test (for seams & joints) Photometer Ambient aerosol must be at least 10 E 3 above FF Maximum Leakage = >FF Scanning rate = 2 inches per 1 inch from joint or seam within clean zone Particle Counter Ambient aerosol must be >300K particles/ft3 Maximum leakage >100 counts Scanning rate = 2 inches per 1 inch from joint or seam within clean zone

185 Photometer vs. Discrete Particle Counter 2005 ISO Cleanrooms & associated controlled environments, Test methods –Installed Filter System Leakage Photometer Upstream challenge aerosol of between 20 & 80ug/l Maximum Leakage = 0.01% Scanning rate = 2 inches per 1 inch from filter face Limitations Efficiency < MPPS Oil aerosols allowed Ability to achieve required concentrations Particle Counter Upstream challenge aerosol (Too much detail to list 6 pages) sufficiently high that N p >2 & <10 Maximum leakage = 0.01% Scanning rate ≤ 3.14 inches per second (varies depending on probe dimensions, N p, sample rate

186 Photometer vs. Discrete Particle Counter 2005 ISO Cleanrooms & associated controlled environments, Test methods –Containment Test Photometer Upstream challenge aerosol of between 20 & 80 ug/l Maximum Leakage = 0.01% Scanning rate ≤ 2 inches per second at 2 inches from joint, seal or mating surfaces Limitations Efficiency < MPPS Oil aerosols allowed Ability to achieve required concentrations Particle Counter The greater of: ambient count X E10 3 > 3.5 E10 6 particles/m 3 Maximum leakage = ≤ ambient count X E10 -2 Scanning rate ≤ 2 inches per second at 2 inches from joint, seal or mating surfaces

187 Photometer vs. Discrete Particle Counter 2001 IH62300:2001 In-Place HEPA Filter testing Photometer Upstream challenge aerosol 10 4 greater than ambient Maximum Leakage = 0.03% Duct measurement-No scan Particle Counter No defined method

188 Photometer vs. Discrete Particle Counter IEST-RP-CC006 Testing Cleanrooms Photometer Upstream challenge aerosol of between 10 to 20 ug/l Maximum Leakage = 0.01% Scanning rate = 2 inches per 1 inch from filter face Particle Counter 3 x E10 8 particle size of interest (10 counts per Appendix B, Exp. 1) Maximum Leakage = 0.01% Scanning rate = [(C c )(L s )(F s )(D p )]÷ [(60)(N p )] Result in or 0.65 inches per second (Appendix B, Exp. 1)

189 Photometer vs. Discrete Particle Counter IEST-RP-CC034 HEPA & ULPA Filter Leak Tests Photometer Upstream challenge aerosol of between 10 to 90 ug/l Maximum Leakage = 0.01% Scanning rate = 2 inches per 1 inch from filter face Particle Counter 2.8 x E10 8 particle size of interest (10 counts per Appendix G, Exp. 1) Maximum Leakage = 0.01% Scanning rate = [(2.8)(108)÷1000][(0.0001) (28.3)(1.25)÷(60)(10)] Result = in or 0.5 in/sec (Appendix G, Exp. 1)

190 Photometer vs. Discrete Particle Counter 2008 NSF 49 Biosafety Cabinetry Particle Counter No defined method Photometer Upstream challenge aerosol of at least 10 ug/l Maximum Leakage = 0.01% Scanning rate = 2 inches per 1 inch from filter face

191 Points to Remember! Photometer & particle counter results are not likely to correlate due to the different weighting of the technology used. –Photometry response is mass weighted while particle response is number weighted. Filter testing process is the same regardless of photometer or particle counter use. –Measure upstream challenge –Measure downstream penetration by scanning or point sampling –Calculate penetration

192 Points to Remember! Filter testing process complexity varies between photometers and particle counters. –Challenge concentration Photometers:Variable range of ug/l with ug/l being typical (Std defined) Particle counters: Variable range of 3.0 E10 5 to 3.0 E10 8 (Std defined, calculated to achieve desired N p ) –Measure Downstream Photometers :0.01% leakage maximum while scanning rate of 2 inches /second in most cases (Std defined) Particle counter: 0.01% leakage maximum in most cases while scanning at a calculated, statistically, determined rate (Std defined)

193 Points to Remember! Calculate Penetration –Photometer:Ratio of upstream challenge to downstream expressed as a percent –Particle counter: Ratio of upstream challenge to downstream expressed as a percent

194 Points to Remember! Each technology has design strengths and weaknesses which decide where its use is “reasonable” in filter leakage testing. –Photometer Aerosol generator for upstream challenge “oil” aerosol No diluter necessary for Upstream measurements Consistent & essentially “Calculation Free” test method Limited to systems with efficiencies ≤99.997% Typically consistent results among multiple units Robust “core” technology –Particle counter Aerosol generator required in most cases, but at a lower output Use of solid or liquid aerosol possible Ability to test systems to % efficiency Diluter required for upstream sampling Unit to unit result consistency difficult to achieve More sensitive detection system results in less-robust instrument

195 Discussion

196 Hands On Demo: Photometer Filter Leak Scanning

197 Review and Discussion

198 Thank you David W. Crosby Tim McDiarmid Don Largent Your logo here. Important: Logo only on FIRST and LAST slides.


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