### CHEMICAL BIOLOGICAL CENTER

U.S. ARMY RESEARCH, DEVELOPMENT AND ENGINEERING COMMAND



### ECBC-CR-085

RESPIRATOR FILTER EFFICIENCY TESTING AGAINST PARTICULATE AND BIOLOGICAL AEROSOLS UNDER MODERATE TO HIGH FLOW RATES

Aaron W. Richardson Jonathan P. Eshbaugh Kent C. Hofacre

BATTELLE MEMORIAL INSTITUTE Columbus, OH 43201-2693

Paul D. Gardner

RESEARCH AND TECHNOLOGY DIRECTORATE

August 2006

Approved for public release; distribution is unlimited.

ABERDEEN PROVING GROUND , MD 21010-5424 

# EDGEWOODDisclaimer
The findings in this report are not to be cons trued as an official Department of the Army position unless so designated by other authorizing documents.

### REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (070 4-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202- 4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty f or failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) XX-08-2006 2. REPORT TYPE Final 3. DATES COVERED (From - To) Dec 2003 - Oct 2005 5a. CONTRACT NUMBER SPO700-00-D-3180 5b. GRANT NUMBER 4. TITLE AND SUBTITLE Respirator Filter Efficiency Testing against Particulate and Biological Aerosols under Moderate to High Flow Rates

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

5e. TASK NUMBER 335 6. AUTHOR(S) Richardson, Aaron W.; Eshbaugh, Jonathan P.; Hofacre, Kent C. (Battelle Memorial Institute); and Gardner, Paul D. (ECBC)

5f. WORK UNIT NUMBER
8. PERFORMING ORGANIZATION REPORT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) AND ADDRESS(ES) Battelle Memorial Institute, 505 Ki ng Avenue, Columbus, OH 43201-2693 DIR, ECBC, ATTN: AMSRD-ECB-RT-PR, APG, MD 21010-5424 ECBC-CR-085

10. SPONSOR/MONITOR’S ACRONYM(S)

11. SPONSOR/MONITOR’S REPORT NUMBER(S) 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) DIR, ECBC, ATTN: AMSRD-ECB-RT-PR, APG, MD 21010-5424

12. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution is unlimited.

13. SUPPLEMENTARY NOTES COR: Paul Gardner, AMSRD-ECB-RT-PR, (410) 436-6692

14. ABSTRACT The growing terrorism threat associated with biological and ch emical agents presents a challenge to emergency responders, healthcare workers, and the civilian population. Currently, Na tional Institute for Occupationa l Safety and Health (NIOSH)- approved respirators are used in various workplace settings to provide protection against harmful aerosols. The primary objective of this project was to evaluate and compare the aeros ol filtration performance of NIOSH-approved respirator filters with non-biological (inert) and biological test aerosols under breathe r flow rates associated with hi gh work rates. The inert test challenges consisted of solid and oil aerosols having nominal diameters ranging from 0.02 to 3.02 μm, spanning the spectrum of potential biological threat agents. As expected , penetration of submicron aerosols was found to increase under increased cyclic and constant flow conditi ons. The magnitude and significance of this increase was dependent on the specific filter type and design. The most penetrating particle size w as generally between 0.1 and 0.2 μm for the P100 filters and 0.05 and 0.10 μm for the N95 filters. Inert aerosols of similar aerodynamic diameter were shown to provide a reasonable estimate of performance against the biological aerosols tested, Bg spores and MS2 phage. The second objective was to assess the extent of reaerosolization of surrogate biological agents from NIOSH-approved filtering facepieces. The extent of reaerosolization was dependent on the particle size, particle type, and loading level. 15. SUBJECT TERMS Filtration efficiency Bioaerosol Biological aerosol Cyclic High flow Aerosol penetration Filter Reaerosolization Breathing Reentrainment
16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON Sandra J. Johnson
a. REPORT

U b. ABSTRACT

U c. THIS PAGE

U UL 181 19b. TELEPHONE NUMBER (include area code) (410) 436-2914 Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18ii Blankiii EXECUTIVE SUMMARY
The growing terrorism threat associated with biological and chemical agents presents a challenge to emergency responders , healthcare workers, and the civilian popul ation. The use of National Institute for Occupational Safety and Health (NIOSH)-approved respirators, if used according to recommended practices, provides prot ection against harmful agents in different workplace settings. Currently, NIOSH certifies resp irators based on an inert aerosol test at a constant flow rate of 85 L/min. However, meas urements of physiological parameters of workers show peak inhalation flow rates for short dura tions in the 300 to 400 L/min range for certain activities that demand high work loads. One objec tive of this study was to investigate the effects of high volumetric and peak flow rates on respirat or filtration performance. In addition, although NIOSH-approved respirator filters have been shown to provide ad equate protection against inert aerosols, their performance with respect to protection against bio aerosols has not been extensively assessed. Thus, another objective of this study was to evaluate and compare the aerosol filtration performance of NIOSH-approved re spirator filters with non-biological (inert) and biological test aerosols.
Four cyclic and three cons tant flow conditions were se lected based on an analysis completed by the U.S. Army's Edgewood Chemi cal Biological Center (ECBC) to assess the relationship between work load and ventilation rate. The cyclic flow conditions have minute volumes ranging from moderate (40 L/min) to high (135 L/min) with peak flows up to 430 L/min. The respirator filters were selected in coordinati on with NIOSH and included two N95 and two P100 filtering facepieces, and two N 95 and two P100 cartridges. The inert aerosol challenges had nominal diameters ranging from 0.05 to 3.0 μ m and were selected to span a range of potential bioaerosol threat agent sizes to include nanopart icles well below the size of bioaerosol threat agents. Oil aerosols were us ed with the P100 filters and solids with the N95 filters. The biological aerosols included bacterial B. globigii (Bg) spores and the virus MS2 phage.
The most penetrating particle size was generally between 0.1 and 0.2 μ m for the P100 filters and 0.05 and 0.10 μ m for the N95 filters. The iner t testing demonstrated that the penetration of submicron particles tends to increase with flow rate or filtration velocity. The magnitude and significance of this increase was dependent on the specific filter design. For example, the SEA HE-T P100 cartridge met the P100 requirement (less than 0.03 percent penetration) even at the highe st cyclic flow conditions. In comparison, the Survivair 1050 P100 cartridge, which has approximately half of the available surface area, had a penetration in excess of 0.1 percent. Although se veral of the filters had penetrations in excess of the NIOSH requirement at the highest flow conditions, the intended use and a ssigned protection factor of the respirator must be considered to determine whet her the increase in penetration is significant.
Comparison of the penetrations measured under constant and cycl ic flow conditions showed that the mean and peak inhalation flow (PIF) rates were important parameters. For the P100 cartridges, similar penetra tions were measured under consta nt and cyclic flow if the constant flow was equivalent to th e mean inhalation flow rate. In contrast to the P100 cartridges, it may be more important to consider the PIF when testing filtering facepi eces or N95 cartridges, especially at the high volumetric flow rates that can be experienced during heavy work loads.iv The N95 filters are not as suitable for the high volumetric flow rate applications as evidenced by their lower surface area as compared to the P100 ca rtridges. Selecting a co nstant flow equivalent to the peak inhalation flow generally provides a conservative estimate of filter performance under cyclic flow conditions.
The filtration efficiency of the N95 a nd P100 filters was also assessed against bioaerosol challenges, Bg spores and MS2 phage , aerosolized both from liquid suspension and a dry powder. The performance of NIOSH-approved N95 and P100 respirator filters was assessed against the bioaerosol challeng es under high volumetric flow conditions. Mean penetrations were below the penetration require ments for the respective filter t ypes (i.e., penetration less than 5 percent for N95 and less than 0.03 percent for P100 filters) under all flow conditions tested. Penetrations of Bg spores through the P100 filters were typically below detectable limits, thus, penetrations were at least an order-of-magnit ude below the P100 requirement. The N95 filters also were very efficient at removing the bacter ial aerosol challenges as average penetrations were less than 0.5 percent. There were no practi cal differences in the penetrations measured using the "wet" and "dry" Bg spore aerosoliza tion methods. The most penetrating of the biological aerosols tested was the "wet" MS2 phage as the particle size was closest to the most penetrating particle size (MPPS) as measured using inert aerosol challenges. Average penetrations through the N95 and P100 filters were typically less than 2 and 0.03 percent, respectively, under all flow conditions. Inert ae rosols of similar aerodynamic diameter were shown to provide a good estimate of performan ce against biological aerosols. The Bg spore "wet" and "dry" aerosol penetrati on was generally within a factor of five of the penetrations measured using the 1.3 μ m PSL. Similarly, the MS2 "wet" ae rosol penetration through the cartridges was within a factor of five of the inert aerosol pene trations measured using the 0.3 μ m PSL. Comparisons were not made with the MS2 "dry" as aerosol penetration was typically below detectable limits. However, this is in agreement with the penetrations measured for the 2.3 μ m PSL. The results demonstrated that tes ting with inert particles in the MPPS range provide a conservative estimate of biological aerosol penetration for those biological aerosols assessed in this study. Finally, the results demons trated that using an optical light scattering instrument such as the LAS to measure bacter ial aerosol penetration provides a conservative estimate of filter performance. This is notable due to the labor intensiv e nature of the bioassay method.
A test method was developed to quantify the extent of reaerosolization from a filtering facepiece loaded with either an inert or biological aerosol. Te sts were performed to assess the effect of particle size, particle type, and loadi ng level. Two brands of filtering facepieces were tested, the MSA Affinity Plus and Gerson 1730. Th e levels and trends of reaerosolization were similar for both brands. For the inert aerosols, reaerosolization was obser ved to increase with increased particle size over the range tested (0.8 to 2.2 μ m). This trend was consistent with that observed by Qian et al. (1997) who attr ibuted this to increased drag for ce on the larger particles.

The extent of reaerosolization of 0.8 μ m particles from filtering facepieces without exhalation valves was very low (less than 0.002 pe rcent or 1 in every 50,0 00 particles loaded). Reaerosolization was observed to increase by an order of magnitude when the same brands of filtering facepieces were tested with exhalation valves. This was attributed to the movement of the valve and localized high veloc ity air that could re-entrain pa rticles collected on the surface ofv the valve or valve housing. Specifically for the 0.8 μ m PSL, the number of particles reaerosolized was observed to increase with increased loading ove r the range from 1 x 10 4 to 1 x 10 6 particles/cm 2 . However, the number of particles did not increase proportionally to the increased loading. Increasi ng the loading by a factor of 10 only increased the number of particles reaerosolized by a fact or of 5. Further work is recommended to determine whether similar trends hold for larger particles.
The percent reaerosolization of the biological aerosols wa s greater than that observed for the inert aerosols with a similar AMMD. For example, reaerosolization of the 0.8 μ m PSL was minimal (~0.002 percent) while reaerosolizat ion of the similarly-sized Bg spores was typically 0.05 to 0.1 percent. Si milarly, reaerosolization of the 2.2 μ m PSL was only 0.01 percent while reaerosolizati on of the comparably -sized MS2 "dry" was 0.5 percent. The higher reaerosolization for the biological aerosols was attri buted to their broader size distribution. For example, the MS2 "dry" ae rosol had significant mass between 2.5 and 5.0 μ m that contained viable particles. As described ab ove, the extent of reae rosolization was shown to increase with increased particle size. Thus, it is important to c onsider the entire size distribution and not just the nominal particle si ze when selecting an inert simulant.
In conclusion, the performance of NI OSH-approved N95 and P100 cartridges and filtering facepieces has been assessed against bot h inert and biological aerosols under high flow conditions representative of ventilation rates duri ng heavy activity. All filters tested were very efficient against the bioaerosols tested in this study as measured penetrations were below NIOSH requirements for all flow conditions tested. The penetrations of inert particles provided a good indication of filter performance against bioaerosols with a similar aerodynamic diameter. When comparing penetrations measured under constant and cyclic flow, those measured at a constant flow equivalent to the cyclic flow MIF pr ovided a good estimate of performance under cyclic flow conditions (i.e., generally within a factor of 2 to 4). Testing at a constant flow equivalent to the PIF results in higher penetr ations than measured under the cyclic flow condition and, thus, would provide a more conservative estimate of pe rformance. All cyclic flow testing performed in this task was done using a sinusoidal flow pr ofile. Additional testi ng is recommended with alternative waveforms such as a trapezoidal wave form to assess the effect of flow profile. Finally, a method was developed to assess reaerosolization of inert and biological aerosols loaded onto a filtering facepiece due to a cough. The extent of reaerosolization was shown to be dependent on particle type, part icle size, and loading level. Further work is recommended to assess the effect of varying th e reentrainment flow profile (e .g., sneeze or cough profiles with different peak flows) and to assess the effect of loading level of pa rticles greater than 1 μ m.vi Blankvii PREFACE
The work described in this report was authorized under Contract No. SP0700-00-D-3180, Task No. 335. This work was st arted in December 2003 and completed in October 2005.

Use of either trade or manufacturers’ name s in this report does not constitute an official endorsement of any commercial products. This report may not be cited for purposes of advertisement.
This report has been approved for public re lease. Registered users should request additional copies from the Defense Technical Information Center; unregistered users should direct such requests to the Nationa l Technical Information Service.
The text of this contractor report is published as received and was not edited by the Technical Releases Office, U.S. Army Edgewood Chemical Biological Center.

Acknowledgments

The authors would like to thank the Office of Law Enforcement Standards, National Institute of Standards and Technology, Gaithersburg, MD, and the National Personal Protective Technology Laboratory (NPPTL), Nationa l Institute for Occupational Safety and Health, Pittsburgh, PA, for funding this project . Special appreciati on goes to Dr. Samy Rengasamy, NPPTL, for his expertise a nd assistance with planning this study.viii Blankix CONTENTS

EXECUTIVE SUMMARY ..................................................................................iii

1.0 INTRODUCTION ................................................................................................ 1
1.1 Background..................................................................................................... 1 1.2 Objective......................................................................................................... 1 1.3 Scope............................................................................................................... 1

2.0 LITERATURE REVIEW ..................................................................................... 2
2.1 Search Strategy ............................................................................................... 2 2.2 Inert Filtration Efficiency ............................................................................... 2 2.2.1 Aerosol Collection Mechanisms............................................................... 3 2.2.2 Effect of Particle Size/Flow Rate.............................................................. 4 2.2.3 Comparison of Constant/Cyclic Flow Penetrations.................................. 7 2.3 Biological Filtration Efficiency ...................................................................... 8 2.3.1 Test Methods............................................................................................. 8 2.3.2 Inert/Biological Pe netration Comparison .................................................10 2.3.3 Effect of Flow Rate...................................................................................13 2.3.4 Viral Filtration Efficiency.........................................................................13 2.3.5 Reaerosolization........................................................................................14 2.4 Summary.........................................................................................................16 2.4.1 Filter Efficiency Testing ...........................................................................16 2.4.1.1 Inert Testing........................................................................................16 2.4.1.2 Biological Testing...............................................................................17 2.4.1.3 Reaerosolization..................................................................................18

3.0 INERT PARTICULATE FILTRAT ION EFFICIENCY TESTING ....................18

3.1 Test Parameters...............................................................................................18 3.2 Test Matrix......................................................................................................21 3.3 Technical Approach........................................................................................22 3.3.1 Model 3160 Automated Filter Tester........................................................22 3.3.1.1 System Description .............................................................................22 3.3.1.2 System Characterization .....................................................................24 3.3.1.3 Test Procedure ....................................................................................24 3.3.2 Large Particle Test System .......................................................................25 3.3.2.1 System Description .............................................................................25 3.3.2.2 System Characterization .....................................................................26 3.3.2.3 Test Procedure ....................................................................................27 3.4 Calculation of Aerosol Penetration.................................................................27 3.5 Inert Results ....................................................................................................28 3.5.1 Effect of High Volumetric Flow Rate.......................................................28 3.5.1.1 Cartridge Filters ..................................................................................28x 3.5.1.2 Filtering Facepieces ............................................................................35 3.5.2 Constant/Cyclic Flow Comparisons .........................................................41 3.6 Inert Aerosol Testing Summary......................................................................44

4.0 BIOAEROSOL FILTRATION EFFICIENCY TESTING...................................45

4.1 Test Parameters...............................................................................................45 4.2 Test Matrix......................................................................................................47 4.3 Technical Approach........................................................................................48 4.3.1 Test System...............................................................................................48 4.3.2 Bioaerosol Generation Methods ...............................................................49 4.3.2.1 Wet......................................................................................................49 4.3.2.2 Dry ......................................................................................................49 4.3.3 Aerosol Sampling and Classification........................................................51 4.3.3.1 Viable Samples ...................................................................................51 4.3.3.2 Optical Particle Counters ....................................................................52 4.3.3.3 Cascade Impactor................................................................................52 4.3.4 System Characterization ...........................................................................53 4.3.5 Test Procedure ..........................................................................................53 4.4 Calculation of Aerosol Penetration.................................................................54 4.5 Bioaerosol Results ..........................................................................................55 4.5.1 Bg Spore Results.......................................................................................55 4.5.1.1 Particle Size Distribution ....................................................................55 4.5.1.2 Bioassay Penetration Results ..............................................................57 4.5.2 MS2 Phage Results ...................................................................................62 4.5.2.1 Particle Size Distribution ....................................................................62 4.5.2.2 MS2 Penetration Results.....................................................................63 4.5.3 Inert Comparisons.....................................................................................66 4.5.3.1 Bg Spores............................................................................................66 4.5.3.2 MS2 Phage..........................................................................................69 4.6 Summary.........................................................................................................71

5.0 REAEROSOLIZATION.......................................................................................72

5.1 Test Parameters...............................................................................................72 5.2 Test Matrix......................................................................................................74 5.3 Test Method ....................................................................................................75 5.3.1 Test System Description ...........................................................................75 5.3.2 Test Procedure ..........................................................................................76 5.3.3 Analytical Methods...................................................................................77 5.3.3.1 Inert Aerosols......................................................................................77 5.3.3.2 Biological Aerosols.............................................................................78 5.3.4 System Characterization ...........................................................................78 5.3.5 Calculation of Reaerosolization................................................................81 5.4 Results .............................................................................................................82 5.4.1 Inert Aerosols............................................................................................83xi 5.4.2 Biological Aerosols...................................................................................85 5.4.2.1 Bg Spores............................................................................................85 5.4.2.2 MS2 Phage..........................................................................................86 5.5 Summary and Discussion................................................................................87

6.0 CONCLUSIONS AND RECOMMENDATIONS ...............................................88

LITERATURE CITED .........................................................................................93

APPENDIXES

A. PHOTOGRAPHS OF CA RTRIDGES AND FILTERING FACEPIECES........................................................................................... A-1

B. RATIONALE FOR SELECT ING FLOW CONDITIONS ......................B-1

C. SHAKEDOWN TESTING OF MODEL 3160......................................... C-1

D. SHAKEDOWN OF TEST SYSTEM FOR LARGE PARTICLE INERT TESTING ..................................................................................... D-1

E. SUMMARY OF MEASURED INERT FILTRATION EFFICIENCIES E-1

F. ESTIMATION METHOD FOR CYCLIC FLOW PENETRATIONS .... F-1

G. MICROBIOLOGICAL METHODS......................................................... G-1

H. SHAKEDOWN TESTING OF THE BIOAEROSOL TEST SYSTEM .. H-1

I. SUMMARY OF BIOAEROSOL PENETRATION RESULTS............... I-1

J. SUMMARY OF REAEROSOLIZATION RESULTS............................. J-1xii FIGURES
1. Four Mechanisms of Particle Capture (DHHS, 2003).......................................... 3
2. Primary Mechanism of Capture for Va rious Particle Diameters Indicating MPPS (DHHS, 2003)............................................................................................ 4
3. Comparison of Sinusoidal Waveforms Used to Assess the Effect of Moderate to High Breather Flows on Filter Performance ................................20

4. Additional HEPA Filters on Dilu tion Air Inlet of Model 3160............................23

5. Lucite Chamber Used to House and S eal Test Filters to the Model 3160............24
6. Test System Used to Measure Penetration of 0.7, 1.3, and 2.9 μm PSL through the N95 Filters .........................................................................................25

7. Effect of Particle Size and Constant Flow Rate on Measured Penetration through SEA HE-T P100 Cartridge ......................................................................29

8. Effect of Particle Si ze and Cyclic Flow Rate on Measured Penetration through SEA HE-T P100 Cartridge ......................................................................29

9. Effect of Particle Si ze and Constant Flow Rate on Measured Penetration through Survivair ® 1050 P100 Cartridge..............................................................30

10. Effect of Particle Si ze and Cyclic Flow Rate on Measured Penetration through Survivair ® 1050 P100 Cartridge ..............................................................30
11. Penetration of 0.1 μm Pa rticles as Function of Face Velocity for SEA and Survivair ® P100 Cartridge Filters ........................................................................31

12. Effect of Particle Size and Constant Flow Rate on Measured Penetration through North 7506 N95 Cartridge.......................................................................32

13. Effect of Particle Si ze and Cyclic Flow Rate on Measured Penetration through North 7506 N95 Cartridge.......................................................................33

14. Effect of Particle Si ze and Constant Flow Rate on Measured Penetration through MSA Flexi-Filter N95 Cartridge .............................................................33

15. Effect of Particle Si ze and Cyclic Flow Rate on Measured Penetration through MSA Flexi-Filter N95 Cartridge .............................................................34xiii 16. Comparison of Ratios of Penetrations Measured through P100 and N95 Cartridges at 180 and 135 L/min...................................................................35

17. Effect of Particle Size and Fl ow Rate on Measured Penetration through 3M TM P100 Filtering Facepiece at Constant Flow..................................36

18. Effect of Particle Size and Fl ow Rate on Measured Penetration through 3M TM P100 Filtering Facepiece at Cyclic Flow ......................................36

19. Effect of Particle Size and Flow Rate on Measured Penetration through Moldex P100 Filtering Facepiece at Constant Flow ...............................37

20. Effect of Particle Size and Flow Rate on Measured Penetration through Moldex P100 Filtering Facepiece at Cyclic Flow ...................................38

21. Effect of Particle Size and Flow Rate on Measured Penetration through Gerson ® N95 Filtering Facepiece at Constant Flow................................39

22. Effect of Particle Size and Flow Rate on Measured Penetration through Gerson ® N95 Filtering Facepiece at Cyclic Flow....................................39

23. Effect of Particle Size and Flow Rate on Measured Penetration through MSA N95 Filtering Facepiece at Constant Flow ....................................40

24. Effect of Particle Size and Flow Rate on Measured Penetration through MSA N95 Filtering Facepiece at Cyclic Flow ........................................40
25. Comparison of Measured Penetratio ns under Cyclic and Constant Flow Conditions with Minute Volumes of 85 L/min.....................................................42
26. Comparison of Penetrations Measured under Constant and Cyclic Flow Conditions for Cartridge Filters............................................................................43
27. Comparison of Penetrations Measur ed under Constant and Cyclic Flow Conditions for Filtering Facepieces......................................................................43
28. Comparison of Penetrations Measur ed under Constant and Cyclic Flow Conditions for P100 Cartridge Filters...................................................................44
29. Schematic of Test System Used to Measure Bioaerosol Penetration ...................48

30. Vilnius Aerosol Generator ....................................................................................50
31. Aerosolization Chamber and Rotary Va ne of Vilnius Aerosol Generator ...........51xiv 32. Size Distribution of “Wet” and “Dry ” Bg Spores Measured Using the Cascade Impactor..................................................................................................56
33. Size Distribution of Bg Spores Measured Using the Aerosizer............................56
34. Size Distribution of Bg Spores Meas ured Using the Aerosizer (Cumulative Number Distribution)............................................................................................57
35. Comparison of Measured Bg “Wet” Penetrations through N95 Filters................59
36. Comparison of Measured Bg “Dry” Penetrations through N95 Filters ................59
37. Comparison of Bg “Wet” and “Dry” Pene trations through Cartridge Filters.......60
38. Comparison of Bg “Wet” and “Dry ” Penetrations through Filtering Facepieces .............................................................................................................60
39. Comparison of Bg Spore Penetratio ns Measured Using the Bioassay Method and LAS-X...............................................................................................61

40. Size Distribution of MS2 “Wet” Meas ured Using the Sierra Impactor................62
41. Size Distribution of MS2 “Wet” Measured Using the LAS-X.............................63
42. Size Distribution of MS2 “Dry” Meas ured Using the Sierra Impactor and Aerosizer ........................................................................................................63
43. Comparison of Measured MS2 “Wet” Penetrations through N95 Filters.............65
44. Comparison of Measured MS2 “Dry” Penetrations through N95 Filters.............65
45. Comparison of MS2 Phage Penetrat ions Measured Using the Bioassay Method and LAS-X...............................................................................................66
46. Comparison of Bg Spore and Inert Penetrations through the North N95 7506 Cartridge ......................................................................................................67

47. Comparison of Measured Inert and Bg Bioaerosol Penetrations Through the North 7506 Cartridge at C onstant Flows of 42.5 and 135 L/min.....68
48. Comparison of Bg Spore and Iner t Penetrations through the MSA N95 Flexi-Filter Cartridge ............................................................................................68
49. Comparison of Bg Spore and Iner t Penetrations through the MSA N95 Affinity Plus Filtering Facepiece..........................................................................69xv 50. Comparison of Bg Spore and Inert Penetrations through the Gerson N95 1730 Filtering Facepiece.......................................................................................69
51. Comparison of MS2 “Wet” and Iner t Penetrations through the North N95 7506 Cartridge...............................................................................................70 52. Comparison of MS2 “Wet” and In ert Penetrations through the MSA N95 Flexi-Filter Cartridge ....................................................................................70
53. Comparison of MS2 “Wet” and In ert Penetrations through the MSA N95 Affinity Plus Filtering Facepiece ..................................................................71
54. Comparison of MS2 “Wet” and Iner t Penetrations through the Gerson N95 1730 Filtering Facepiece...............................................................................71
55. Cough Profile for Reaerosolization Testing .........................................................74
56. Schematic of Reaerosolization Test System.........................................................76
57. Analysis Patterns on 47-mm Collecti on Filters Used with Fluorescent Microscope to Quantify Load ings of Inert Particles.............................................78
58. Comparison of Target and Measured Cough Profile Used for Reaerosolization Testing.................................................................................79
59. Comparison of Number of Particle s Collected on Pre- and Post-Cough Filters for Tests Performed with the 0.8 μm PSL .................................................80
60. Comparison of Number of Particle s Collected on Pre- and Post-Cough Filters for Tests Performed with the Biological and Inert Aerosols .....................81
61. Comparison of Percent Reaerosolizati on of Inert Particles from MSA and Gerson Filtering Facepieces..................................................................................84
62. Comparison of Percent Reaerosoliz ation of 0.8 μm PSL from Gerson Respirator with Exhalation Va lve Protected during Loading...............................84
63. Comparison of Percent Reaerosoliz ation of 0.8 μm PSL from Gerson Respirator at Loadi ngs Ranging from 1 x 10 4 to 1 x 10 6 Particles/cm 2 ................85
64. Comparison of Inert and Bg Spore Reaerosolization Results...............................86
65. Comparison of Inert and MS2 Phage Reaerosolization Results ...........................87xvi TABLES
1. Influence of Filtration Velocity and Ae rosol Size on Collection Mechanisms .... 4
2. Summary of Cartridges a nd Filtering Facepieces.................................................19
3. Summary of Challenge Aerosols for Testing N95 and P100 Filters ....................19
4. Summary of Cyclic Flows Used for Tes ting with the Inert Aerosol Challenges..20
5. Test Matrix Completed to Assess the Effect of High Cyclic Flows on Filtration Performance of Ca rtridge Respirator Filters....................................21
6. Test Matrix Completed to Assess the Effect of High Cyclic Flows on Filtration Performance of Filtering Facepieces................................................22
7. Comparison of Face Velocities for P100 and N95 Cartridges..............................34
8. Test Matrix Completed to Assess Filter Performance under Cyclic Flow Conditions Using a Bioaerosol Challenge ............................................................47
9. Test Matrix Completed to Assess Fi lter Performance under Constant Flow Using a Bioaerosol Challenge...............................................................................47
10. Particle Size Range Six-Stage Cascade Impactor.................................................53
11. Comparison of “Wet” and “Dry” Bg Size Distributions ......................................55
12. Comparison of Penetration Measured Using Bioassay Method and Bg Spore “Wet” Aerosol Challenge under Constant and Cyclic Flow Conditions ..............58
13. Comparison of Penetration Measured Using Bioassay Method and Bg Spore “Dry” Aerosol Challenge under Constant and Cyclic Flow Conditions...............58
14. Comparison of “Wet” and “Dry” MS2 Aerosol Size Distributions......................62
15. Comparison of Penetration Measur ed Using Bioassay Method and MS2 “Wet” Aerosol Challenge under Constant and Cyclic Flow Conditions ..............64
16. Comparison of Penetration Measur ed Using Bioassay Method and MS2 “Dry” Aerosol Challenge under Constant and Cyclic Flow Conditions...............64
17. Estimated Surface Areas of N95 Filtering Facepieces .........................................73
18. Test Matrix Completed to Assess Reaerosolization .............................................75
19. Summary of Reaerosolization Results..................................................................831 RESPIRATOR FILTER EFFICIENCY TES TING AGAINST PARTICULATE AND
BIOLOGICAL AEROSOLS UNDER MO DERATE TO HIGH FLOW RATES

1.0 INTRODUCTION

1.1 Background

The growing terrorism threat associated with biological and chemical agents presents a challenge to emergency responders, healthcare wo rkers, and the civilian population. Currently, National Institute for Occupational Safety and H ealth (NIOSH)-approved respirators are used in various workplace settings to provide protection ag ainst harmful aerosols. Particulate respirator filters are certified using an inert aerosol at a fl ow rate of 85 L/min. While this is sufficient to ensure protection in most situations when us ed according to recommended practices, it is unknown how these filters would perform at higher fl ow rates or against a biological aerosol that
could be encountered in an act of terrorism. A rigorous, de finitive study assessing respirator filter performance challenged w ith bioaerosols has not yet been conducted to fully address particle size dependence. In a ddition, investigations on the eff ects of high volumetric and peak flow rates on respirator filtration performance associated with high work rates are lacking.

1.2 Objective

The primary objective of this task was to evaluate and compare the aerosol filtration performance of NIOSH-approved re spirator filters with non-biologi cal (inert) and biological test aerosols under high breather flow rates. In addition, penetratio ns measured under constant and cyclic flow conditions were compared. Finally , the extent of reaerosolization of surrogate biological agents from NIOSH-approved filt ering facepiece mask s was characterized.

1.3 Scope

The literature review comple ted to identify previous effo rts to assess the effects of particle size, particle type, a nd/or flow condition on the performa nce of particulate respirator2 filters is described in Section 2.0. Section 3.0 desc ribes the test matrices, methods, and results of the inert filtration efficiency testing perfor med at the U.S. Army's Edgewood Chemical Biological Center (ECBC). A sim ilar summary of the bioaerosol testing performed at Battelle
follows in Section 4.0. The test method develo ped for reaersolizati on and the results are
discussed in Section 5.0. Conclusions and r ecommendations are provid ed in Section 6.0.

2.0 LITERATURE REVIEW

2.1 Search Strategy

A literature search was completed to identify previous efforts to assess the effects of particle size, particle type, a nd/or flow condition on the performa nce of particulate respirator filters. The purpose of the search was to help define the test parameters and matrices for this task. The search included the open literature, test standards, and the Chemical Biological Information Analysis Center (CBIAC) and De fense Technical Information Center (DTIC) databases. A partial list of search terms included: filter, re spirator, efficiency, penetration, cyclic, breather, aerosol, and biological. In addition, a sear ch of the open literature was completed to identify previous work assessi ng reaerosolization of bi ological aerosols from filtering facepieces. A partial list of key words us ed in the search included: filter, respirator, bioaerosol, reaerosolization, and reentrainment. Limited information was identified on the reaerosolization of particles from filter materials. The title, aut hor, and abstract of each record were reviewed to identify the potentially relevant articles.

2.2 Inert Filtration Efficiency

The most relevant studies are summari zed below following a brief overview of the primary mechanisms for aerosol collection and th e influence of filtration velocity and aerosol size on each mechanism (S ection 2.2.1). A number of studies that assessed the effect of both particle size and constant flow rate on measured penetration ar e reviewed in Section 2.2.2. Two studies that compare penetrations measured under constant and cyclic flow are reviewed in
Section 2.2.3.3 2.2.1 Aerosol Collection Mechanisms

Particle penetration is depende nt on several parameters includ ing the aerosol particle size, filtration velocity (based on flow rate and available surface area), and several filter parameters including the thickness, fiber diameter, and solidity or fiber packing density (i.e ., ratio of solid fiber volume to gross filter volume). The four primary collection mechanisms, illustrated in Figure 1, for aerosol filtration are: (1) inertial imp action, (2) interception, (3) diffusion, and (4) electrostatic (Hinds, 1999). Th e general trends regarding the in fluence of filtration velocity
and aerosol size on the mechanisms are summar ized in Table 1. Particles less than 0.1 μ m are most effectively collected by the diffusion m echanism. Diffusion occurs when the random (Brownian) motion of a particle causes that particle to contact a fiber. As velocity is increased, collection by diffusion is reduced. Interception occu rs when a particle does not deviate from the stream line but is intercepted by the fiber (i.e., streamline passes within one particle radius of fiber). Interception is the most important collection mechanism for particles in the most penetrating particle size (MPPS) an d is independent of velocity. Inertial impaction occurs when a particle deviates from the streamline around th e fiber and collides with the fiber. This mechanism is most effective for larger particles and is enhanced by higher particle velocities.
The electrostatic mechanism is an enhancement to mechanical filtrati on. Electret media are made of dielectric materials that have a significa nt microscopic bipolar charge on the fibers with a low net macroscopic charge. Charged particles are attracted to oppositely charged fibers by the Coulombic force. Neutral particles are coll ected by the polarization force induced by local
electric fields within the filter media.

Figure 1. Four Mechanisms of Particle Capture (DHHS, 2003)4 Table 1. Influence of Filtration Velocity and Aerosol Size on Collection Mechanisms
Mechanism Increased Filtration Ve locity Increased Aerosol Size Inertial Impaction Collection Increased Collection Increased Interception Independent of Velocity Collection Increased

Diffusion Collection Reduced Collection Reduced Electrostatic Collection Reduced Collection Reduced
The three primary collection mechanisms, diffusion, interception, and impaction, are effective over different partic le sizes. The MPP through a fi lter exists where none of the mechanisms is dominant. This generally occurs between 0.05 and 0.5 μ m depending on the filter properties and filtration ve locity (Hinds, 1999). A generic illustr ation of the effect of particle size on filtration efficiency is provided in Fi gure 2. The figure also indicates where each collection mechanism is predominant over the pa rticle size range. Penetration generally increases with increased flow rate or velocity in the region of the MPPS because the diffusion collection mechanism is reduced. This also ge nerally leads to a shift in the MPPS toward smaller particles. Collection efficiency of larg er particles can actually increase with increased velocity as the inertial impac tion mechanism is enhanced.

Figure 2. Primary Mechanism of Capture for Various Particle Diameters Indicating MPPS (DHHS, 2003)

2.2.2 Effect of Particle Size/Flow Rate

Several published studies have assessed the effect of particle si ze and/or flow rate on the measured efficiency of respirator filters in cluding: Ruuskanen et al. (1988), Brosseau et al.5 (1989); Stevens and Moyer (1989), Fardi and Lui ( 1991), Chen et al. (1992) , Qian et al. (1998), Hanley and Foarde (2003). The challenge ae rosols employed consisted mainly of chargeneutralized dioctyl phthalate (DOP), sodium chlori de (NaCl), corn oil, or polystyrene latex (PSL) spheres. The aerosol concentrations upstream and downstream of the filter were typically analyzed using a laser aerosol spectrometer (L AS) or condensation nucleus counter (CNC) for particle sizes in the submicrometer range. For particles larger than 1 μ m, researchers frequently used an aerodynamic particle sizer (APS, TSI Inc., Shoreview, MN) or aerodynamic size spectrometer (Aerosizer ® , Amherst Process Instruments Inc., Hadley, MA). In general, the
studies were conducted at constant flow rates ra nging from 16 to 85 L/min using a variety of disposable dust-mist (DM), dust-fume-mist (DFM), and high-efficiency particulate air (HEPA) respirator filters. These resp irator filters were certified under the requirements of 30 CFR 11 (1972), which has since been replaced by 42 CFR 84 (1995). Stevens and Moyer (1989) evaluated the effect of a “worst-case” ae rosol on the filtration efficiency of a variety of DM, DF M, and high-efficiency respirator filters. The most penetrating particle sizes were determined as a function of test flow rate. Filters were challenged with either solid NaCl aerosol or liquid DOP aerosol w ith numerical median di ameters (NMDs) ranging
from 0.03 to 0.3 μ m and constant flow rates ranging from 16 to 85 L/min. The particle size of maximum penetration varied with filter type and flow rate, and was less than 0.25 μ m NMD in all cases. As the flow rate was increased, th e magnitude of penetrati on increased and a shift towards a smaller particle size for maximum penetr ation was observed. This is consistent with the mechanisms described above. At the most pe netrating conditions, the high-efficiency filters provided greater than 99.97 pe rcent efficiency, while the DM and DFM respirators had efficiencies ranging from 67 to 89 percen t and 85 to 99 percent, respectively. Brosseau et al. (1989) evalua ted electrostatic DM respirat ors from ten manufacturers challenged with monodisperse PSL part icles ranging in size from 0.102 to 2.02 μ m. Filter penetration was greatest for particles 0.1 μ m in diameter, which was consistent with the results of Stevens and Moyer (1989). In addition, appreciable differences were found in the performances of filters distributed by the ten different manufacturers, where filter penetration ranged from about 5 to 15 percent for the most penetrating particle sizes. Fardi and Liu (1991) challenged DM and DF M respirators composed of charged and uncharged fibers using monodisper se NaCl and DOP particles with diameters in the range of6 0.035 to 0.4 μ m. Tests were conducted at constant fl ow rates ranging from 16 to 48 L/min, and aerosol penetration measurements were ma de using a condensation nucleus counter, aerodynamic particle sizer, and laser optical pa rticle counter for purposes of comparison. Results obtained by these instruments were in ag reement with each other in the overlapping size range of the instruments. The most penetrating particle size was found to be approximately
0.1 μ m for filters containing charged fibers and 0.3 to 0.4 μ m for mechanical filters. Consistent with Stevens and Moyer (1989), for all filters test ed there was an increase in penetration with increasing particle size for small particles until a maximum was reached, and then penetration decreased with particle size for larger particles. For the range of respirator filters tested, the peak penetration varied from 1.2 to 30 percent at 16 L/min, 3.5 to 37 percent at 28 L/min, and 6 to 45 percent at 48 L/min. There was no significant difference in penetration between solid NaCl and liquid DOP particles of the same size. Chen et al. (1992) assessed aeros ol penetration as a function of particle size for several filtering facepieces and DM, DFM, and HEPA respir ator cartridges using corn oil particles over a size range of 0.1 to 15 μ m. Tests were conducted at consta nt flow rates ranging from 5 to 100 L/min. The respirators were sealed to a mannequin head form during testing. Results showed an increase in aerosol penetration with increasing flow rate in the submicrometer size range, leading the authors to concede that th e primary removal mechanisms are diffusion and
electrostatic attraction within th is size range. The penetration of supermicrometer-sized aerosol particles decreased with mask flow, indicat ing removal of large particles by impaction. Only a limited number of recent studies were identified that have evaluated N-, R-, and P-type respirators certified under 42 CFR 84. Qi an et al. (1998) compared the measured filtration efficiency of NIOSH-approved N95 respirators with that of DM and DFM respirators using challenge aerosols of NaCl and PSL particles with sizes ranging from 0.1 to 5.10 μ m. Tests were conducted at constant flow rates of 32 and 85 L/ min. N95 respirators were found to have higher filtration efficiencies than DM a nd DFM respirators, showing at least 95 percent efficiency against particles at the most penetrating partic le size (0.1 to 0.3 μ m). The filtration efficiency increased with size, reaching appr oximately 99.5 percent or higher at about 0.75 μ m. In a more recent study, Hanley and Foarde ( 2003) assessed the filtration efficiency provided by the C2A1 canister against an in ert potassium chloride aerosol (0.3 to 10 μ m) over a range of constant flow rates (30, 50, and 80 L/ min). The results demonstrated that the7 penetration rapidly decreased as th e particle size increased above 0.3 μ m, and penetration of particles ranging from 0.3 to 0.7 μ m increased with higher flow rate . Penetrations could not be accurately measured for pa rticles greater than 0.7 μ m as the downstream aerosol concentrations
were below the detection limit of the aerosol particle counter, demonstrating the difficulty in generating sufficient challenge concentrations of the larger particles to accurately measure penetrations of high-efficiency filters. Martin and Moyer (2000) evaluated seve ral N95, N99, R95 and P100 electrostatic respirator filters to determine filter efficiency and most penetrating particle size. Challenge aerosols included NaCl (0.075 μ m NMD, 1.86 GSD) and DOP (0.185 μ m NMD, 1.60 GSD), and
a constant flow rate of 85 L/min was used fo r N95 filters and 42.5 L/min for N99, R95, and P100 filters. Tests involved comparing “as received” filters to those dipped in isopropanol to remove the electrical charge associated with the filter fibers. All of the filters tested which had the electrostatic charge removed showed a dramatic increase in filter penetration. For the NaCl aerosol, N-series filters increased in maximum pe netration from less than 5 percent up to 35 to 55 percent. Similarly, the maximum penetrati on increase with the R 95 filters was from 0.03 percent up to 50 percent and for the P100 filters fr om 0.001 to 4 percent. In addition, there was a shift in the most penetr ating particle size from approximately 0.05 to 0.10 μ m for the new filters toward larger sizes in the 0.25 to 0.35 μ m range once the electrostatic charge was removed.

2.2.3 Comparison of Constant/Cyclic Flow Penetrations

A limited number of studies were identified th at assessed the effect of cyclic flow on filter performance. The two mo st relevant studies were by Stafford et al. (1973) and Brosseau et al. (1990). Stafford et al. (1973) measured the pe netration of monodisperse PSL (0.176 to 2.02 μ m) and DOP (0.3 μ m) aerosols through respirator filter cart ridges at three cyclic flows with mean flow rates of 30, 35, and 53 L/min. These flows we re selected to correspond to work rates of 415, 622, and 830 kg-m/min. Tests were also conducte d at a constant flow rate of 16 L/min (equivalent to 32 L/min through a pair of cartrid ges). At steady-flow conditions, the maximum penetration occurred at a particle size of 0.3 μ m, which is consistent with theoretical single-fiber predictions. However, during cyclic flow the particle size that produced maximum penetration8 varied between filters, in one case less then 0.3 μ m and in the other approximately 0.5 μ m. Also, the maximum penetration was considerably hi gher than corresponding steady-flow values, suggesting that tests conducted under steady-fl ow conditions may provide a considerable overestimate of filter performance. Brosseau et al. (1990) compared the collec tion of silica and asbestos aerosols by DM respirators under breathing and constant flows. The cyclic flow was sinusoidal with a mean flow of 76 L/min and a peak flow of 100 L/min, and represented a work rate of 622 kg-m/min. The constant flow rate was 32 L/min. In general, the silica penetration under cyclic flow conditions was about one and a half times as great as that measured under steady flow conditions, which is
consistent with the results of Sta fford et al. (1973). The asbestos results were inconclusive as the results varied by filter.

2.3 Biological Filtration Efficiency

The majority of research published in the open literature has fo cused on evaluation of surgical masks and a variety of disposable dust-mist (DM), dust-fume-mist (DFM), and highefficiency particulate air (HEPA) respirator filters for protec tion against bacterial aerosols (Brosseau et al., 1994; Chen et al., 1994; J ohnson et al., 1994; Willeke et al., 1996; Brosseau et al., 1997; McCullough et al., 1997 ; Wake et al., 1997; Qian et al., 1998).

2.3.1 Test Methods

Previous studies were largely conducted to assess use of respirators in controlling healthcare-worker exposures to infec tious biological aerosols, namely Mycobacterium
tuberculosis , the organism which causes tuberculosis. The studies used bacterial test aerosols including M. chelonae , M. abscessus , Bacillus subtilis , B. megatherium , B. alcalophilus , Streptococcus salivarius , Staphylococcus epidermidis , Pseudomonas fluorescens , P. alcaligenes , and Micrococcus luteus to simulate pathogenic organisms such as M. tuberculosis . No studies were identified in the open lite rature that assessed viral aerosol penetrat ion through respirator
filters.9 Test system designs and methodologies empl oyed for evaluating mask and respirator filter efficiency against biological aerosols varied between different research groups. Brousseau et al. (1994) used a co lumn apparatus with ve rtical airflow to minimize aerosol losses to the duct walls by sedimentation. The mask or respirator filter was sealed with wax onto a metal plate within the duct. Measurements upstream and downstream of the filter were corroborated with Andersen cascade impactor s and an aerodynamic particle sizer (APS, TSI Inc.), which measures the aerosol concentrati ons of viable and total particles, respectively. By comparison, Willeke et al. (1996) conducted te sts using a rectangular test chamber with perforated metal sheets at the top and bottom of the chamber to ensure a uniform aerosol concentration in the vicinity of the test mannequi n. The mask or respirator was sealed to the mannequin head form with silicone adhesive or petroleum jelly. Upstream and downstream particle concentrations were measured with an aerodynamic size spectrometer (Aerosizer ®

, Amherst Process Instruments Inc.) Finally, Wake et al. (1997) designed a test system which was comprised of two aerodynamically identical flow lines, one of which contained the mask or respirator filter while the other served as a reference line. The mask or filter was sealed with PVC tape or hot-melt adhesive within the flow line, and the downstream aerosol concentrations were measured using all glass impingers (AGI) for both the filtered a nd reference lines. The penetration through the filter was obtained from the ratio of the filtered and reference lines. The bacterial aerosols were typically aerosolized using a 6-jet Collison nebulizer (BGI Inc.) operated at pressures ranging from 7 to 15 psi. McCullough et al. (1998) found that reducing the nebulizer operating pressure to 3 psi increased the percentage of culturable particles
of M. abscessus from 15 to 45 percent. Generated challenge concentr ations, if reported, were generally in the range of 10 4 to 10 6 colony forming units (CFU)/m 3 air, the higher concentration being used to provide a suffici ent downstream concentration wh en testing the most efficient
filters. Most studies were conducted under constant airflow rates ranging from 16 to 85 L/min. As alluded to above, a variety of techniques have been used to measure th e challenge and filtered
aerosol concentrations. Tota l particle analyzers used include the APS, Aerosizer ® , and LAS. Viable particle samplers include the Andersen six-stage impactor , membrane filters, and AGIs. Viable sampling involves collecting and transf erring the sampled organisms onto growth media to allow the organism to replicate for enumera tion. Organism viability can be reduced due to aerosolization, transport, and sampling. Total pa rticle analyzers meas ure both viable and10 non-viable particles, therefore aerosol concen tration measurements are higher than those determined by viable samplers. Strong correla tion of filter penetration measured by viable samplers and the APS has been reported (Brous seau et al., 1994; Chen et al., 1994; McCullough et al., 1997; Johnson and Andersen, 1996). In some cases, it was not ed that the filter penetrations were slightly lower for the Anders en impactor (Chen et al., 1994) and AGI (Johnson and Andersen, 1996) compared to the APS. However, because of the strong correlation, researchers suggest that a total pa rticle analyzer may be used in place of more labor-intensive viable sampling techniques for de termining bioaerosol penetration. A single test standard was identified for ev aluating the filtration e fficiency of medical face mask materials using a biol ogical aerosol (ASTM F 2101-01, 2001). A bacterial aerosol of
S. aureus is generated from a suspension using a nebuliz er, with a target mean particle size of
3.0 μ m. Tests are conducted under a constant fl ow rate of 28.3 L/min. A six-stage Cascade impactor is used to measure the aerosol penetr ation downstream of the filter. The reported maximum filtration efficiency that can be m easured using this method is 99.9 percent.

2.3.2 Inert/Biological Penetration Comparison

Several studies have compared measured pe netrations of inert a nd biological aerosols through masks and respirator filters. Qian et al. (1998) evaluated the unloaded filtration efficiency of NIOSH-approved N 95 respirators using challenge aerosols of polydisperse NaCl particles (0.1 to 0.7 μ m), monodisperse polystyrene latex (PSL) spheres (0.60, 1.02, 2.94, 3.96,
and 5.10 μ m), and two bioaerosols, B. subtilis (mean aerodynamic diameter 0.8 μ m) and B. megatherium (mean aerodynamic diameter 1.2 μ m). Tests were conducte d at a constant flow rate of 85 L/min. For both bacteria, the filtr ation efficiency of the N95 respirator was 99.5 percent or higher, equivalent to the data for the inert particles of the same aerodynamic
diameter. Brousseau et al. (1994) compared filtra tion efficiencies of the bioaerosol M. chelonae (0.78 μ m NMAD, 1.2 GSD) to inert aerosols contai ning either monodisperse PSL particles (0.804 μ m) or dioctyl phthalat e (DOP) particles (0.12 μ m NMAD, 1.5 GSD) for various layers of fiberglass flatsheet filter media. Tests were conducted at a steady flow rate of 46 L/min. Results indicated no significant difference in pe netration through flatsheet fiberglass filter media11 when challenged with M. chelonae and PSL particles of the same aerodynamic size. In addition, penetration of DOP particles as measured with an optical particle counter were closely correlated with the penetration of M. chelonae measured by the Andersen impactor and APS, as well as PSL particles measured by the APS. Based on their results, Brousseau et al . suggest that an inert aerosol with aerodynamic particle size similar to a bioaerosol of interest is an appropriate test aerosol to predict bioaer osol filter collection. Under equivalent test conditi ons, Chen et al. (1994) report this same conclusion for experiments with a surgical mask and severa l disposable DM, DFM, and HEPA respirators against challenge aerosols of M. chelonae and PSL particles. Mean efficiencies for viable
M. chelonae ranged from 97 percent for the surgical ma sk and DM respirator to more than 99.99 percent for the HEPA respirator. Mean effi ciencies for the PSL particles were slightly lower in some cases, ranging from 96 percent for th e surgical mask and DM respirator to more than 99.99 percent for the HEPA respirator. Chen et al. raised the question about practical significance of the measured diffe rences between the f ilters tested in thei r study (less than 3 percent), when it has been estimated that at leas t 10 to 20 percent leakage occurs in masks not properly fitted to the wearer’s face. Wake et al. (1997) evaluated the filter efficien cy of several respirator filters, disposable dust masks, and surgical masks against the bioaerosols B. globigii , M. luteus , and P. alcaligenes , monodisperse urea aerosols (1.5, 3, 5, 7, and 9 μ m), and a NaCl aerosol (0.6 μ m MMAD, 2.3 GSD). Bacterial penetration generally corresponded to those of non-biological aerosols of similar size, but no direct comparisons were made . Bacterial penetration ranged from less than 0.01 percent to 0.88 percent for various glass fiber a nd wool resin respirator filters, compared to up to 1.56 percent for the 1.5 μ m urea particles and up to 0.31 percent for the NaCl particles. Hanley and Foarde (2003) assessed the filtration efficiency provided by the C2A1 canister against a bioaerosol of B. globigii (Bg) spores over a range of constant flow rates (30, 50, and 80 L/min). For comparison, tests were al so completed with a polydisperse potassium chloride aerosol with particle s ranging in size from 0.3 to 10.0 μ m. Samples of the challenge and downstream aerosol were collected on polycarbona te membrane filters with a pore size of
0.4 μ m. Downstream samples were collected on filte rs with a diameter of 142 mm to allow the full canister flow to be passed th rough the filter without excessive pressure drop. All measured efficiencies with the bioaerosol challenge ex ceeded 99.99997 percent. In 31 of 33 tests, no Bg12 spores were detected downstream of the C2A1 canister. The results demonstrated that inert aerosol penetration in the 0.7 to 1.0 μ m size range were consistent with those measured using the Bg spore challenge. Previous reports on filter performance agai nst particles of vari ous sizes, shapes and aspect ratios contain conflicting results. Wille ke et al. (1996) compared penetrations through surgical masks and DM respirators of several rod-shaped bacteria ( B. megatherium , P. fluorescens , B. alcalophilus ) of varying aspect ratios with that of spherical S. salivarius and inert corn oil particles. Results indicate the penetration of spherical S. salivarius bacteria were approximately the same as spherical corn oil particles in the aerodynamic size range from 0.9 to
1.7 μ m. The penetration of rod-shaped bacteria was lower than S. salivarius , and decreased with increase of aspect ratio showing that filter pene tration of bacteria is a strong function of their shape. As an example, Pseudomonas fluorescens , with an average aspect ratio of 3, was found to penetrate 50 to 60 percent less than spherical particles of the same aerodynamic diameter. Willeke et al. postulated that due to greater su rface area of non-spherical particles compared to spherical ones, interception a nd electrostatic attraction caus e greater removal (i.e., less penetration) for rod-shaped b acteria compared to spherical particles of the same aerodynamic
size. In comparison, McCullough et al. (1997) evaluated the penetration of M. abscessus (mean aerodynamic diameter 0.69 μ m), B. subtilis (mean aerodynamic diameter 0.88 μ m), and S. epidermidis (mean aerodynamic diameter 0.87 μ m) bioaerosols, along with a monodisperse PSL aerosol (0.55 μ m) through a variety of DM and DFM resp irator filters and surgical masks. In all cases, penetration of the PSL aerosol was gr eater than any of the bi ological aerosols due to its smaller aerodynamic diameter. However, the penetration of B. subtilis (a rod) was found greater than S. epidermidis (a sphere) at approximately the same aerodynamic diameter. Contrary to Willeke et al. (1996), the authors suggested that the aerodynamic diameter of the bacteria may not be an accurate predictor of aerosol penetrati on for non-spherical particles in these filters, particularly when electrostatic forces are dominant. Particle shape was also found to influence pe netration through fibrous filters. Tuinman and Steeenweg (1998) compared aerosols with several shapes including rod-shaped caffeine particles, angular urea pa rticles, plate-like eico sanoic acid particles, a nd needle-shaped arachidic acid particles to spherical oil particles with an equivalent part icle size distribution13 (approximately 0.04 to 0.8 μ m). The penetration decreased fro m spherical particles to angular particles and rods to the lowest penetration fo r plates. The reduction in penetration for rod-shaped particles compared to spherical particles was cons istent with the findings of Willeke et al. (1996) for rod-shaped bacteria with aspect ratio si milar to the caffeine particles.

2.3.3 Effect of Flow Rate

Several studies have been conducted assessing th e effects of flow rate on filter efficiency of biological aerosols. Willeke et al. (1996) evaluated constant air flow rates ranging from 16 to 80 L/min to simulate breathing ra tes representative of conditions ranging from rest to strenuous work. Increasing the flow to 50 and 80 L/mi n resulted in increased penetrations of P. fluorescens through a DM respirator of 6 and 8 per cent, respectively. Th e effect was most significant for particles less than 1 μ m in aerodynamic diameter. Bros seau et al. (1997) assessed the effect of flow rate (45 and 85 L/min) a nd relative humidity (30 and 70 percent) on the penetration of M. abscessus aerosol through 16 respirator filt ers and 5 surgical masks. The median penetration of M. abscessus at 45 L/min was 2, 0.4, and 0.02 percent for DM, DFM, and HEPA filters, respectively. Increas ing the flow rate to 85 L/min resulted in greater penetration, and changes in relative humidity caused mini mal effects on bioaerosol collection. McCullough et al. (1997) reported similar results for a variety of respirator filters and surgical masks against three bacterial aerosols ( M. abscessus , S. epidermidis , B. subtilis ) under the same flow rate and relative humidity conditions. Only one study, co nducted by Johnson et al. (1994), was identified in the open literature that test ed a biological aerosol using cycl ic rather than constant flow
conditions. Johnson et al. simu lated normal breathing during light exertion using an automated breathing simulator (TSI Inc.) operated at a brea thing rate of 15 breaths/min, tidal volume of 1.5 L/breath, and minute volume of 22.5 L/min.

2.3.4 Viral Filtration Efficiency

Research efforts on respirator filter efficiency have largely focused on bacterial aerosols,
thus limited information on viral aerosols was f ound. Harstad and Filler (1969) evaluated the performance of ultra-high-efficiency filter pape rs against the submicron viral aerosol of T114 bacteriophage (0.12 μ m NMD) and the bacterial aerosol of B. globigii spores (1.0 μ m NMD). Submicron phage aerosols were generated using a Dautrebande aerosol generator, Bg spore aerosols using a vaponefrin nebulizer, and aero sol concentration was measured upstream and downstream of the test filter using AGIs. Ph age penetration through filters averaged 0.00095 percent, and increased markedly (up to 0.39 perc ent) with an increase in velocity up to 150 ft/min and neutralizing with bi polar air ions. Penetration of bacterial spore aerosols through the filter papers was essentially zero. Hofacre et al. (1996) measured the penetra tion of a viral aerosol of MS2 phage and a monodisperse PSL aerosol (0.173 μ m) through a HEPA filter used for collective protection. The MS2 phage aerosol concentrations upstream and downstream of the filter were measured using both a bioassay enumeration technique and a ligh t scattering instrument. The inert aerosol concentrations were measured using the light scattering instrument. Aerosol penetration measured using the light scatteri ng technique was statistically e quivalent for both the MS2 phage and PSL particles, while the pe netration of MS2 phage measured using the bioassay method was consistently lower. The study concluded that inert aerosols of si milar size provided a conservative indication of HEPA filter performance against a bioaerosol.

2.3.5 Reaerosolization

Qian et al. (1997a) evaluated the reaerosoli zation of inert and bi ological aerosols from three different models of N95 half-mask respirat ors at velocities up to 300 cm/sec, intended to represent violent sneezing or coughing. The filters were loaded with aerosols of either NaCl (0.15 to 1.0 μ m), PSL (0.60, 1.02, 2.94, 3.96, and 5.10 μ m), or the bacterium B. subtilis or B. megatherium . The flow rate during loading was a c onstant 85 L/min and the environmental conditions were ambient (T =25oC, RH=22%). The particle loading (1x10 5 particles/cm 2 ) was the same for both the inert and biological aerosols. A quick release valve was used to pulse the airflow in the opposite direction of loading to simulate the cough or sneeze. An aerosol size spectrometer (Aerosizer ® , Amherst Process Instruments, Hadl ey, MA) was used to measure the concentration up- and downstream of the filter. For each filter model, Na Cl particle penetration was less than 5 percent, thus satisfying the certifi cation requirement of 95 percent or more collection efficiency. Reaeros olization was found insignifican t for particles less than 1.0 μ m,15 with less than 0.025 percent becoming reentraine d. For the condition of violent sneezing or coughing, only larger particles were reaerosolized in significant am ounts, with about 1 percent of
3 μ m and 6 percent of 5 μ m PSL particles. This is of im portance as single bacteria may aggregate or attach to inert particles to form la rger clusters, increasing their risk of potential reaerosolization. In addition, re sults indicate that bacteria b ecome reentrained at high air velocities more easily than the NaCl particles of similar size, which the authors reason may signify a weaker bond to the filter fibers or more surface area exposed to th e airflow. Finally, no reaerosolization of particles was observed when the relative humidity was increased to 35 percent, which the authors attribute to liquid bridging between particles and filter fibers that
increases the adhesion force. In a related study, Qian et al. (1997b) assessed the effects of particle size, inert particle type, filter type, and reentrainment velocity on re aerosolization of inert aerosols including NaCl, PSL, corn oil, and dust. Similar test methods were used as described above. Flat sheets of three types of fibrous filter media used in half-mask respirators were evaluated. The collection efficiency of the filters ranged fr om approximately 93 percent for 0.6 μ m particles to 99.8 percent for 5.1 μ m particles. Reaerosolizat ion trends were in agr eement with the previous study as reaerosolization of 0.6 to 5.1 μ m particles increased approxima tely with the square of particle size and the square of reentrainment velocity, and decreased with relative humidity.
Reaerosolization was also found to be a function of the particle type as dust was found to have the highest reentrainment, while co rn oil was not reentrained at a ny of the test conditions. This
was attributed to differences in interaction with the filter fibers of oily particles compared to solid, irregularly shaped particles. Consistent with previous st udies, electrostatic charges on the filter fibers significantly increased the collection of submicrometer particles; however, particle reaerosolization was only slightly impeded by the embedded charges. Finally, filter properties were found to significantly aff ect particle reaerosolization. The number of reaerosolized particles decreased slightly with filter thickne ss, which supports the concept that most of the particles are reentrained from the front layer of the filter. Essentially no particle reentrainment was observed from charged felt, compared with up to 5 to 15 percent from glass fiber HEPA and polypropylene filters.
Reentrainment of bioaerosols from air ventilat ion filters has also recently been studied. Jankowska et al. (2000) compared the collection efficiency and r eentrainment rate of the fungal16 spores Penicillium brevicompactum and P. melinii against that of inert potassium chloride (KCl) particles using a medium prefilter and a higher efficiency fine f ilter. The fungal spores were aerosolized from an agar surface, simulating dr y spore dispersion. Solid KCl particles were aerosolized from an aqueous solution using a Co llison nebulizer. The aerosol concentrations upand downstream of the filter were measured using an Aerosizer ® . Filter loading ranged from approximately 10 5 to 10 6 particles/cm 2 . The collection efficiency was found to be slightly lower for fungal spores than for KCl particles of th e equivalent aerodynamic size. Reaerosolization increased with reentrainment velocity for all test particles. When the reentrainment velocity was the same as the loading velocity, the reaeroso lization was less than 0.4 percent. When the reentrainment velocity was increased to 3.0 m/s, the reaerosolization of fungal spores was higher than that of KCl particles, ranging from 2 to 6 percent for P. brevicompactum , 5 to 12 percent for
P. melinii , and 0.2 to 0.6 percent for KCl particles. The higher reen trainment of fungal spores was attributed to the presence of aggregated s pores, such that the reentrainment velocity may become sufficient to break up the aggregates and reentrain the spores. The differences between fungal spores were attributed to surface structure, where P. melinii spores have a spiny surface imparting weaker contact with the filter fibers.

2.4 Summary

This section provides a brief summary of th e trends observed in the literature and the impact on the current study. In a ddition, it identifies the da ta gaps in the lite rature and how they pertain to goals of the current study.

2.4.1 Filter Efficiency Testing

2.4.1.1 Inert Testing. Numerous studies were identifie d in the literature review that assessed the effect of flow rate and particle size on the measured aerosol penetration through particulate respirator filters. However, no studie s were identified that assess the effect of high volumetric flow rates that may be encountered during heavy work rates on filter performance.
Few studies in the literature a ssessed filtration performance above 85 L/min constant flow and
none above 100 L/min. The results have shown that penetration of submicron particles,17 specifically those in the MPPS range, tend to incr ease with increased flow rate. The MPPS is generally in the range of 0.1 to 0.3 μ m depending on the type of filter. Particles larger than 1 μ m have been shown to be collected more efficientl y at higher flow rates as inertial impaction is
enhanced. Previous studies have also demonstr ated that even N95 filters are very efficient (>99.5%) at removing particles above 0.7 μ m. To this end, the particle sizes tested in this study were focused on those in the MPPS region. Five pa rticle sizes were tested over the range from
0.02 to 0.3 μ m and only three particle sizes greater than 0.3 μ m. Few studies were identified that assessed aerosol filtration performance under cyclic
flow conditions. The studies that were review ed concluded that highe r penetrations were measured under cyclic flow conditions, correspo nding to various work rates, than measured
under constant flow rates used in test standards (i.e ., 32 or 85 L/min). There is considerable debate regarding the impact of the peak inha lation flow on filter performance, both from an aerosol and gas/vapor filt ration perspective. No conclusions could be drawn from the literature as to the impact of peak flow or what an approp riate constant flow rate is to provide an estimate of performance under cyclic flow. As this is an important objective of the current study, the constant flows were matched to the cyclic flow minute volume, mean inhalation flow, or peak inhalation flow to permit comparisons.

2.4.1.2 Biological Testing. In summary, appreciable differences were found in the performance of respirator filters when challenged with biological aerosols. Overall, studies have confirmed that N95 and HEPA respirators are su bstantially more efficient than DM and DFM respirators and surgical masks ag ainst biological aerosols. Cons istently, no signifi cant difference in filter penetration was found be tween spherical inert and spheri cal bioaerosol particles of similar aerodynamic diameter, sugges ting that inert particles of the same size may be used to predict bioaerosol efficiency. In some cases, th e penetration of rod-shaped bacteria was lower than that of spherical organisms of the same aerodynamic diameter, indicati ng that in addition to particle size, particle shape may also affect penetration through respirator filters. Finally, increases in flow rates to levels representa tive of heavy working conditions were found to increase biological aerosol penetration, particularly for submic rometer particles. This becomes critically important when c onsidering that a certain numbe r of pathogenic organisms of18 submicrometer size may be sufficient to cause a se rious health risk. No studies were identified in the literature that assessed viral penetr ation through particulat e respirator filters.

2.4.1.3 Reaerosolization. Particle size, shape and com position, air velocity, humidity, and filter properties were all fa ctors found to significantly affect particle reentrainment from filter materials. Large particles of approximately 5.0 μ m diameter and greater were found to be most susceptible to reaerosolization. Biologica l particles were found to become reentrained more easily than inert particles of comparable size, which is suspected to result from weaker contact with filter fibers due to irregular sh apes and surface characteristics. In addition, aggregation of bacteria and fungal spores to form larger clusters was determined to also increase potential reaerosolization.

3.0 INERT PARTICULATE FILTRATION EFFICIENCY TESTING

Currently, NIOSH-approved particulate air purifying respirator filters are tested against
salt or oil aerosols at a constant flow rate of 85 L/min for certification per 42 CFR Part 84 (1995). However, measurements of physiological parameters of workers show peak inhalation
flow rates from 300 to 400 L/min for short durati ons during certain high work load activities (Caretti et al., 2004). As discussed in Section 2.0, studies to determ ine the effect of high breather flows on the filtration efficiency of NIOSH-appr oved particulate filters are lacking in the open literature. This section describes the testing comp leted to assess the effect of particle size, flow rate, and flow condition (i.e., cycl ic versus constant) on filtrati on of inert aerosols. The two primary objectives of the inert testing were: (1) assess the effect of high volumetric flow conditions on the performance of NIOSH-approved particulate respirator filters and (2) compare performance under constant and cyclic flow conditions.

3.1 Test Parameters

The filters, summarized in Table 2, were selected in consultation with NIOSH and included two N95 filtering facepi eces, two P100 filtering facepiece s, two N95 cartridges, and two P100 cartridges. The two brands of commer cial P100 filtering facepieces used in the study19 had exhalation valves. The valves were not sealed during the iner t filtration efficiency testing. Photographs of each filter are provided in Appendix A. The filters were not preconditioned prior to testing (i.e., tested as-received). The envir onmental conditions during testing were maintained at ambient temperature (25 ± 3°C) and relative humidity (40 ± 10%). Table 3 summarizes the challenge aerosols and the target particle sizes. Solid aerosols (i .e, salt and PSL) were used with
the N95 filters and oil aerosols (i.e., Emery 3004 and DOP) were used with the P100 filters. This approach is consistent with how certification testing is performed by NIOSH (42 CFR 84, 1995). For each particle size, the challe nge aerosol concentration was ade quate to measure efficiencies of at least 99.97 percent.

Table 2. Summary of Cartridg es and Filtering Facepieces Filter Type Rating Model Manufacturer N95 Flexi-Filter MSA (Pittsburgh, PA) N95 7506 North Safety Products (Cranston, RI) P100 HE-T SEA (Branford, CT) Cartridge P100 1050 Survivair (Santa Ana, CA) N95 1730 Louis M. Gerson, Co., Inc. (Middleboro, MA) N95 Affinity Plus MSA (Pittsburgh, PA) P100 8293 3M (St. Paul, MN) Filtering Facepiece P100 2360 Moldex-Metric, In c. (Culver City, CA)

Table 3. Summary of Challenge Aeroso ls for Testing N95 and P100 Filters Filter Type N95 P100 Target NMAD ( μ m) Challenge Aerosol 0.02, 0.05, 0.1, 0.2, 0.3 NaCl DOP 0.7, 1.3, 2.9 PSL Emery 3004

Tests were performed over a range of constant and cyclic flow conditions. The rationale for selection of the flow conditions is provided in Appendix B. As noted in the appendix, the cyclic flow conditions were sel ected to simulate work intensities ranging from moderate to
exhaustive. The selected flow conditions are based on studies performed with unmasked subjects and, thus, are likely extreme under co nditions of respirator wear. The breathing machine used in this study produced a sinusoidal waveform. The cyclic flow conditions with corresponding peak inhalation flow (PIF) and me an inhalation flow (MIF) are summarized in Table 4 and compared graphically in Figure 3. The MIF is the average flow rate over the20 inhalation portion of the breathing cycle. The PIF represents the maximum flow rate obtained over the inhalation cycle. For a sinusoidal waveform, the PIF is π times the minute volume. The
constant flow rates were selected to match a cyclic flow minute volume, MIF, or PIF for comparison purposes. These were 85 ± 5, 270 ± 15, and 360 ± 20 L/min. For example, the 85 L/min constant flow matches a cyclic flow mi nute volume (2.3 L tidal volume, 37 breaths/min) and a MIF (1.6 L tidal volume, 25 breaths/min). Since all single cartridges were from dualcartridge respirators, they were tested at half of the tidal volum e or constant flow rate stated previously.

Table 4. Summary of Cyclic Flows Used for Testing with the Inert Aerosol Challenges Breathing Rate

(breaths/min) Tidal Volume (L) Minute Volume (L/min) PIF (a) (L/min) MIF (b) (L/min) 25 1.6 40 130 85 (c) 37 2.3 85 270 (c) 175 42 2.7 115 360 (c) 230 44 3.1 135 430 270 (c) (a) Peak inspiratory flow rate assuming ideal sinusoidal waveform (b) Mean inspiratory flow rate assuming ideal sinusoidal waveform (c) Selected for constant flow testing

-500 -400 -300 -200 -100

0 100 200 300 400 500

0 0.5 1 1.5 2 2.5

Time (sec)Flow Rate (L/min) 1.6 L Tidal Vol, 25 BPM 2.3 L Tidal Vol, 37 BPM 2.7 L Tidal Vol, 42 BPM 3.1 L Tidal Vol, 44 BPM

Figure 3. Comparison of Sinusoidal Waveforms Used to Assess the Effect of Moderate to High Breather Flows on Filter Performance21 3.2 Test Matrix

The test matrices for the cartridges and f iltering facepieces are provided in Tables 5 and 6, respectively. The tables indicate the num ber of tests performed at each combination of filter, particle size, and flow condition. The 0.02 to 0.3 μ m aerosol challenges have been grouped since the efficiencies were measured se quentially using the same cartridge or filtering facepiece, as will be described in Section 2.3.1. Similarly, the 0.7 and 1.3 μ m particle sizes have been grouped. Only two replicat es were performed with the 2.9 μ m challenge at each flow condition due to the high efficiency of the filters . The results demonstrat ed that the penetration
of 2.9 μ m particles was less than 0.0 01 percent for all conditions tested. Tests were not performed with the filtering facepieces at the hi ghest cyclic flow cond ition for particle sizes ranging from 0.02 to 0.3 μ m due to problems generating a stable challenge with the proper
aerosol size distribution at this flow condition.

Table 5. Test Matrix Completed to Assess the Effect of High Cyclic Flows on Filtration Performance of Cartridge Respirator Filters
Constant Flow (L/min) Cyclic Flow (L/min) 42.5 135 180 20 42.5 57.5 67.5 Filter Target NMAD ( μ m) # Tests Completed 0.02, 0.05, 0.1, 0.2, 0.3 3 3 3 3 3 3 3 0.7, 1.3 3 3 3 3 3 3 3 North N95 2.9 2 2 2 2 2 2 2 0.02, 0.05, 0.1, 0.2, 0.3 3 3 3 3 3 4 3 0.7, 1.3 3 3 3 3 3 3 3 MSA N95 2.9 2 2 2 2 2 2 2 0.02, 0.05, 0.1, 0.2, 0.3 3 3 3 3 3 3 3 0.7, 1.3 3 4 3 3 3 4 3 SEA P100 2.9 2 2 3 2 2 2 2 0.02, 0.05, 0.1, 0.2, 0.3 3 3 3 3 3 3 3 0.7, 1.3 3 3 3 3 3 3 3 Survivair P100 2.9 2 2 2 2 2 3 322 Table 6. Test Matrix Completed to A ssess the Effect of High Cyclic Flows on Filtration Performance of Filtering Facepieces
Constant Flow (L/min) Cyclic Flow (L/min) 85 270 360 40 85 115 135 Filter Target NMAD ( μ m) # Tests Completed 0.02, 0.05, 0.1, 0.2, 0.3 3 5 6 3 3 3 0 (a) 0.7, 1.3 3 3 3 3 3 3 3 MSA N95 2.9 2 2 2 2 2 2 2 0.02, 0.05, 0.1, 0.2, 0.3 3 3 3 3 3 3 0 (a) 0.7, 1.3 3 3 3 3 3 3 3 Gerson N95 2.9 2 2 2 2 2 2 2 0.02, 0.05, 0.1, 0.2, 0.3 3 3 3 3 1 3 0 (a) 0.7, 1.3 3 3 3 3 3 3 3 3M P100 2.9 3 3 3 3 3 3 3 0.02, 0.05, 0.1, 0.2, 0.3 3 3 3 3 3 0 (a) 0 (a) 0.7, 1.3 3 3 3 3 3 3 3 Moldex P100 2.9 3 4 4 4 3 3 3 (a) Stable challenge could not be generated using TSI Model 3160 Auto mated Filter Tester.

3.3 Technical Approach

This section describes the test systems and procedures that we re used to measure the inert
filtration efficiencies. A modified Model 3160 Automated Filter Tester (TSI, Shoreview, MN) was used for testing with the 0.02 to 0.3 μ m aerosols, and is describe d in Section 3.3.1. Due to limitations with the Model 3160, a separate te st system was used for the 0.7, 1.3, and 2.9 μ m aerosols, and is desc ribed in Section 3.3.2.

3.3.1 Model 3160 Automated Filter Tester

3.3.1.1 System Description. The Model 3160 consisted of four primary components: (1) aerosol generation system, (2) aerosol sensing devices, (3) filter holder, and (4) vacuum pump or breathing machine. The aerosol gene ration system consisted of an atomizer and electrostatic classifier (EC). Th e atomizer generated a polydisperse oil or salt aerosol that was passed through the EC to generate the desired monodisperse aero sol at the desired particle size. The aerosol exiting the EC was diluted with HEPA-filtered room air. The aerosol number concentrations up- and downstream of the test filter were measured simultaneously using two condensation particle counters (CPCs). The upstream CPC (Model 3760A, TSI, Shoreview,23 MN) sampled at 1.5 L/min and the downstr eam CPC (Model 3762, TSI, Shoreview, MN) sampled at 3.0 L/min. The higher sample flow rate on the downstream CPC increased the sensitivity of the Model 3160 and allowed shorte r sample durations. The upstream sample was diluted by a factor of approximately 100 prio r to measurement using a diluter (Model 3302A, TSI). The dilution factor was adjustable base d on the expected challenge concentration. A vacuum pump was used to pull the desired constant flow rate through the te st filter. The flow rate was measured using a mass flow me ter (Series 4000, TSI, Shoreview, MN).
Several modifications were made to the M odel 3160 to permit efficiency measurements over the range of flow conditions. First, additiona l HEPA filters were inst alled at the dilution air inlet, as shown in Figure 4. Second, a 1.5 hp vacu um pump was added for testing at constant flows in excess of 150 L/min, and a breathing machine was adapted for cyclic flow testing. Finally, the test filters were housed in a Lucite ® chamber, measuring approximately 22x18x10 cm, that was sealed between the filter chucks as shown in Figure 5. The aerosol entered the chamber through a 7.5-cm hole on top of the chamber. The filt ering facepieces were placed over a similar sized hole in the bottom of the chamber and sealed using an adhesive. Threaded fittings were machined to mate with the cartridges.

Figure 4. Additional HEPA Filters on Dilution Air Inlet of Model 3160 Added HEPA Filters24 Figure 5. Lucite ® Chamber Used to House and Seal Test Filters to the Model 3160

3.3.1.2 System Characterization. Shakedown tests were conducted to characterize the test system and establish the pr oper operating conditions. This in cluded assessing the effect of non-isokinetic sampling, flow calibrations, and char acterization of the ch allenge particle size
distribution. The shakedown testi ng is detailed in Appendix C.

3.3.1.3 Test Procedure. Prior to testing a filter, the dilution ratio on the upstream CPC was verified at a specific particle size and fl ow condition. This was done without a test filter (i.e., cartridge or filtering facep iece) to ensure no sampling bi as between the up and downstream samples (i.e., measured penetration was 100 pe rcent indicating agreement between the up- and downstream CPCs). The sample bi as test results are provided in Appendix C. With the dilution ratio set, the cartridge or filteri ng facepiece was mounted to the Lucite ® chamber and the
chamber sealed to the Model 3160. The vacuum pump or breathing machine was connected to the test system and set to the proper c onditions. The Model 3160 was programmed to sequentially measure efficiencies at the following particle si zes: 0.02, 0.05, 0.1, 0.2, and 0.3 μm. The Model 3160 was started and automatically ste pped through the particle sizes and measured the efficiencies. When complete, the vacuum pump or breathing machine was stopped and the filter removed from the test system and discarded.25 3.3.2 Large Particle Test System

The Model 3160 was unable to prod uce particles greater than 0.4 μ m under high flow conditions due to limitations of the system. This section describes the test system and approach
used to measure filter efficiencies with challenge aerosols ranging from 0.7 to 2.9 μ m.

3.3.2.1 System Description. The test system, pictured in Figure 6, consisted of an aerosol generation system, exposure chamber, filter holder, breathing machine (or vacuum pump), and aerosol sampling/classification system . For the N95 filters, a Collison nebulizer was

Figure 6. Test System Used to Me asure Penetration of 0.7, 1.3, and 2.9 μ m PSL through the N95 Filters

used to aerosolize PSL particle s suspended in distilled water. A 24-jet Collison (BGI Inc., Waltham, MA) was used to aerosolize the 2.9 μm PSL and a 6-jet Collison (BGI Inc., Waltham, MA) was used to aerosolize the 0.7 and 1.3 μm PSL. For the P100 filters, a 6-jet Collison nebulizer was used to aerosolize Emery 3004 oil. The nebulizer produced a polydisperse oil aerosol with sufficient numbers of 0.7, 1.3, and 2.9 μm particles to measure efficiencies of at least 99.97 percent. The aerosol exiting the nebulizer was mixed with filtered house air before passing through a neutralizer (Mod el 3012, TSI, Shoreview, MN). The generator continuously delivered aerosol-laden air to the exposure cham ber to ensure a stable aerosol challenge was26 maintained. Additional dilution air was pulled, as needed, thr ough two HEPA filters located on top of the chamber. The chamber contained mixing fans to ensure a well-mixed challenge atmosphere. Chamber pressure was measured using a magnehelic ® pressure gauge. Excess challenge was vented through HEPA filters and exhausted into the room. The filter holder was mounted on the bottom of the chamber. The design of the filter holder was specific to the filter being tested. Fo r the filtering facepieces, the holder consisted of a cone with a flat plate at the top. The filtering facepiece was sealed to the flat plate using rope caulk. For the cartridges, threaded fittings were machined. The filter holder was mounted to a
2.5-cm OD stainless steel bulkhead fitting that passed through the bottom of the chamber. The filter holder was connected to the breathing mach ine with large diameter (~2.5 cm OD) flexible tubing. The breathing machine allowed for the ad justment of the tidal volume and breathing rate. The challenge-laden atmosphere was pulle d through the test filter during inhalation. The breathing machine was equipped with a check valve such that the exhaled air was exhausted into the room after being filtered. The test system was also set up such that the test filter (i.e., cartridge or filtering facepiece ) was bypassed during system startup to minimize loading since the objective of this effort was to measure the initial penetration. The aerodynamic particle sizer (APS, Mode l 3321, TSI, Shorevie w, MN) and diluter (Model 3302A, TSI, Shoreview, MN) were used to measure the challenge and downstream
aerosol concentrations. The chamber containe d a stainless steel prob e that extended 10 cm beyond the chamber wall for collecting samples of the challenge atmosphere. The downstream aerosol concentration was sampled from a sma ll chamber (cylindrical in shape with 15 cm diameter and 25 cm length) equipped with a stainless steel sample probe that extended approximately 7.5 cm into the chamber. Testing w ithout a filter in the ho lder was completed to assess potential sampling bias on the measured penetrations due to the non-isokinetic sampling
downstream.

3.3.2.2 System Characterization. Shakedown tests were completed to verify the proper operating conditions of the system. This included no-filter testing to identify any potential sampling bias between the up- and downstream samples and characterizing the challenge aerosol. The shakedown testing is detailed in Appendix D.27 3.3.2.3 Test Procedure. The filter was mounted to the test fixture. The outlet valves on the P100 filtering facepieces were not sealed dur ing testing. The test chamber was sealed and the breathing or vacuum pump, as appropriate, was started. The challenge generation system was started and permitted to ope rate for 10 to 20 minutes depending on the flow condition to allow the aerosol to reach a steady state concentration. During this time, the cartridge or filtering facepiece was bypassed to minimize filter loading. When steady state was reached, the valves were adjusted such that flow was pulled through the test filter. A sample of the challenge aerosol
was collected with the APS for two minutes. Ne xt, the sampling line was switched to sample downstream of the filter and adequate time was gi ven for the instrument to stabilize. The downstream sample duration was varied to pr ovide adequate time to permit efficiency measurements of at least 99.97 percent based on th e challenge concentrati on. For the N95 filters, the sample duration was five minutes when testing 0.7 and 1.3 μ m particles and 15 minutes during testing with the 2.9 μ m particles. The longer sample duration was needed
with the 2.9 μ m PSL particles because the challenge con centration was lower. The P100 filters required 15 minutes of downstream sampli ng when testing with the 0.7, 1.3, and 2.9 μ m oil challenge particles. After sampling downstream was complete, the sample line was switched to the upstream and a second two minute sample of th e challenge concentration was collected. If the two challenge samples (i.e., before and af ter downstream sampling) were not within 20 percent of each other, the test was repeated as the challenge aerosol was not stable. After the challenge sample was collected, the aerosol generation system was stopped and the chamber flushed. The filter was removed from the test sy stem and discarded, and a new filter was tested.

3.4 Calculation of Aerosol Penetration

The percent aerosol penetration (P) was defi ned as the ratio of the downstream aerosol concentration (C Down ) to the challenge aerosol concentration (C Chal ):

100 (%) × =
Chal Down C C P

Alternatively, the filtration efficiency ( η ) was defined as:

100 1 100 (%) × ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

− = − =
Chal Down C C P η28 The concentrations were the average number concentrations measured by the aerosol sensing instrument (i.e., APS or CPC). The challenge concentration was the average of the challenge measurements made before and after the downstream sample.

3.5 Inert Results

The inert testing had two primary objectives: (1) assess the effect of high volumetric flow rates on performance of NI OSH-approved respirator filters over a range of particle sizes and (2) compare performance under constant and cyclic flow conditions. The results that address each objective are discussed in Sections 3.5.1 and 3.5.2, respectively.

3.5.1 Effect of High Volumetric Flow Rate

This section summarizes the results of the inert testing. Penetrations were measured as a function of both flow rate and particle size. The cartridge results are summarized in Section 3.5.1.1 and the filtering facepieces follow in Se ction 3.5.1.2. A complete summary of the measured penetrations for each tr ial is provided in Appendix E.

3.5.1.1 Cartridge Filters. The effects of particle size and flow condition on measured penetrations for the SEA HE-T and the Survivair ® P100 cartridges are shown in Figures 7 through 10. The constant and cy clic flow conditions are provid ed in separate figures. The
horizontal red line identifies the maximum allowable penetr ation based on the NIOSH P100 requirement (0.03%). Each data point repres ents the mean penetration and the error bars represent the 95 percent confidence in tervals. The solid lines represent the best fit regressions. Both filters were extremely efficien t for particles between 0.7 and 2.9 μ m as penetrations were typically less than the minimum detection limit of 0.0001 percent at all flow conditions. Thus, the regressions provided are based on the particle sizes ranging from 0.02 to 0.3 μ m. The most penetrating particle size (M PPS) was between 0.1 to 0.2 μ m for both filters under both constant and cyclic flow. The MPPS shifted toward the lowe r end of this range as the flow rate increased.
This observation is consistent with the litera ture (Stevens and Moyer, 1989). The primary collection mechanisms for particles in this ra nge are interception and diffusion. The diffusion29 mechanism becomes less efficient as the filtration velocity increases leadi ng to a decrease in the
MPPS.

0.0001 0.001

0.01

0.1

1

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%) 42.5 L/min
135 L/min
180 L/min

Figure 7. Effect of Particle Size an d Constant Flow Rate on Measured Penetration through SEA HE-T P100 Cartridge

0.0001

0.001

0.01

0.1

1

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%) 20 L/min [MIF = 42.5 L/min] 42.5 L/min [PIF = 135 L/min] 57 L/min [PIF =180 L/min] 68 L/min [MIF = 135 L/min]

Figure 8. Effect of Particle Size an d Cyclic Flow Rate on Measured Penetration through SEA HE-T P100 Cartridge30 0.0001

0.001

0.01

0.1

1

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%)

42.5 L/min
135 L/min
180 L/min

Figure 9. Effect of Particle Size an d Constant Flow Rate on Measured Penetration through Survivair ® 1050 P100 Cartridge

0.0001

0.001

0.01

0.1

1

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%) 20 L/min [MIF = 42.5 L/min] 42.5 L/min [PIF = 135 L/min] 57 L/min [PIF =180 L/min] 68 L/min [MIF = 135 L/min]

Figure 10. Effect of Particle Size a nd Cyclic Flow Rate on Measured Penetration through Survivair ® 1050 P100 Cartridge31 The SEA HE-T filter met the requirement for a P100 filter across all pa rticle sizes at all
flow conditions tested. Penetra tions in excess of 0.03 percent were measured for the Survivair ® filter. This is potentially due to differences in surface areas between th e two filters. The SEA filter has approximately double the surface area and, thus, the filtration velocity would be half that of the Survivair filter at an equivalent flow rate. The measured penetrations of 0.1 μ m particles (approximately the MPPS) under constant flow conditions are plotted as a function of filtration velocity in Figure 11. Note that the measured penetrations are similar at equivalent face velocities. Based on Figur e 11, the filters exceed 0.03 per cent penetration when the face velocity exceeds approximately 3.3 cm/sec.

0.0001

0.001

0.01

0.1

1

0.1 1 10 Face Velocity (cm/s)Penetration (%) 0.1 um - SEA P100
0.1 um - Survivair P100

Figure 11. Penetration of 0.1 μ m Particles as Function of Face Velocity for SEA and Survivair ® P100 Cartridge Filters

The effects of particle size and flow c ondition on measured penetrations through the North 7506 and MSA Flexi-Filter N95 cartridges ar e shown in Figures 12 through 15. Both filters efficiently removed particles greater than 1 μ m as penetrations were less than 0.1 percent regardless of flow condition. As observed for th e P100 cartridges, the pe netration of submicron particles tended to increase with increased flow rate. For both N95 cartridge filters, the MPPS was approximately 0.05 μ m and generally independent of flow rate. This MPPS was smaller as32 compared to that observed for the P100 filters. Th is could be due to higher filtration velocities as compared to the P100 cartridges that contained pleated media. The estimated surface areas and corresponding face velocities at the three constant flow rates are compared in Table 7. Recall, the MPPS is expected to decrease as the face velocity increases. The smaller MPPS could also
be attributed to differences in the media type (i.e., electrostatic property, fiber diameter, solidity, thickness). However, evaluation of these prope rties was beyond the scope of this effort.
Penetrations of 0.02 and 0.05 μ m particles through the North cartridge exceeded 10 percent at the highest flow conditions. Based on its small size and low surface area, it is not suitable for use under the high flow conditions evaluated in this study.

0.0001

0.001

0.01

0.1

1 10 100

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%)

42.5 L/min

135 L/min

180 L/min

Figure 12. Effect of Particle Size a nd Constant Flow Rate on Measured Penetration through North 7506 N95 Cartridge33 0.0001

0.001

0.01

0.1

1 10 100

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%)

20 L/min[MIF = 42.5 L/min] 42.5 L/min [PIF = 135 L/min] 57 L/min [PIF = 180L/min] 68 L/min [MIF = 135 L/min]

Figure 13. Effect of Particle Size a nd Cyclic Flow Rate on Measured Penetration through North 7506 N95 Cartridge

0.0001

0.001

0.01

0.1 1 10 100

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%)

42.5 L/min 135 L/min 180 L/min

Figure 14. Effect of Particle Size a nd Constant Flow Rate on Measured Penetration through MSA Flexi-Filter N95 Cartridge34 0.001

0.01

0.1

1 10 100

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%)

20 L/min [MIF = 42.5 L/min] 42.5 L/min [PIF = 135 L/min] 57 L/min [PIF = 180 L/min] 68 L/min [MIF =135 L/min]

Figure 15. Effect of Particle Size and Cy clic Flow Rate on Measured Penetration through MSA Flexi-Filter N95 Cartridge

Table 7. Comparison of Face Veloci ties for P100 and N95 Cartridges Flow Rate (L/min) 42.5 135 180 Filter Estimated Surface Area (cm 2 ) Face Velocity (cm/s) SEA P100 1,000 0.7 2.2 2.9 Survivair P100 400 1.7 5.5 7.3 MSA N95 100 7.1 23 30 North N95 50 14 45 60

As discussed above, the penetration thr ough both the P100 and N95 cartridges tended to increase with increased flow rate. However, the magnitude of this increase was dependent on filter type and particle size. Fo r example, Figure 16 compares the ratios of penetrations at 180 and 135 L/min for each cartridge. For the P100, th e largest increases were seen with the 0.02 μ m particles. It should be noted that both P100 filters effectivel y filtered the 0.02 μ m particles even at the highest flow rates as penetr ations were less than the 0.03 percent requirement. In contrast, increases in penetration across the particle size s shown was fairly uniform for the N95 filter but the highest increases in penetr ation were observed for the 0.3 μ m particles.35 0.1

1 10 100

0.01 0.1 1 10 Particle Size ( μ m)Ratio (P180 L/min:P135 L/min) SEA P100 Survivair P100 MSA N95 North N95

Figure 16. Comparison of Ratios of Pe netrations Measured through P100 and N95 Cartridges at 180 and 135 L/min

3.5.1.2 Filtering Facepieces. The effects of particle size and flow condition on measured penetration through the 3M TM P100 filtering facepiece are shown in Figures 17 and 18. Regressions were not provided due to the extrem ely poor fit to the data. The MPPS was 0.02 to
0.05 μ m. As seen with the cartridges, the 3M filt er was very efficient against the 1.3 and 2.9 μ m challenges as penetrations were less than 0.001 pe rcent. The penetration of submicron particles was highly dependent on flow conditions. Simila r trends were observed for the constant and cyclic flow conditions. Pe netrations of 0.02 to 0.01 μ m particles increased by more than an order of magnitude between the lo west and highest flow rates.36 0.0001

0.001

0.01

0.1

1

0.01 0.1 1 10 Particle Size ( μ m)Penetration (%) 85 L/min
270 L/min
360 L/min

Figure 17. Effect of Particle Size a nd Flow Rate on Measured Penetration through 3M TM P100 Filtering Facepiece at Constant Flow

0.0001

0.001

0.01

0.1

1

0.01 0.1 1 10 Particle Size ( μ m)Penetration (%) 40 L/min (cyclic) [MIF = 85 L/min. PIF = 130 L/min] 85 L/min (cyclic) [MIF = 175 L/min, PIF = 270 L/min] 115 L/min ( cyclic) [MIF = 230 L/min, PIF = 360 L/min]

Figure 18. Effect of Particle Size a nd Flow Rate on Measured Penetration through 3M TM P100 Filtering Facepiece at Cyclic Flow37 The effects of particle size and flow c ondition on measured penetration through the
Moldex ® P100 filtering facepiece are shown in Figures 19 and 20. For the constant flow testing the penetrations increased more than an order-of -magnitude as the flow increased from 85 to
270 L/min. Penetrations did not increase significan tly when tested at 360 L/min. The MPPS at
85 L/min was 0.05 μ m and penetrations clearly declined as particle size increased or decreased. In fact, the penetrations measured between 0.05 and 0.3 μ m particles varied by more than an order of magnitude. In comparison, the penetrat ions measured over the same particle size range at 270 and 360 L/min varied by less than a factor of two.

0.0001

0.001

0.01

0.1

1 10

0.01 0.1 1 10 Particle Size ( μ m)Penetration (%) 85 L/min 270 L/min 360 L/min

Figure 19. Effect of Particle Size a nd Flow Rate on Measured Penetration through Moldex P100 Filtering Facepiece at Constant Flow38 0.0001

0.001

0.01

0.1

1 10

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%) 40 L/min [MIF = 85 L/min]
85 L/min [PIF = 270 L/min]

Figure 20. Effect of Particle Size a nd Flow Rate on Measured Penetration through Moldex P100 Filtering Facepiece at Cyclic Flow

The effects of particle size and flow condi tions on measured penetrations through the
Gerson ® and MSA N95 filtering facepi eces are shown in Figures 21 through 24. Penetrations of
1.3 and 2.9 μ m particles were less than 1 percent under all flow conditions. Penetration of submicron particles increased significantly between 85 and 270 L/min constant flow. The penetrations for each particle size at 270 and 360 L/ min were similar. Penetrations of particles
between 0.02 and 0.3 μ m were greater than 5 percent at the highest flow conditions tested.39 0.01

0.1

1 10 100

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%) 85 L/min

270 L/min

360 L/min

Figure 21. Effect of Particle Size a nd Flow Rate on Measured Penetration through Gerson ® N95 Filtering Facepiece at Constant Flow

0.01

0.1

1 10 100

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%) 40 L/min [MIF = 85 L/min] 85 L/min [PIF = 270 L/min] 115 L/min [PIF = 360 L/min]

Figure 22. Effect of Particle Size a nd Flow Rate on Measured Penetration through Gerson ® N95 Filtering Facepiece at Cyclic Flow40 0.01

0.1

1 10 100

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%) 85 L/min
270 L/min 360 L/min

Figure 23. Effect of Particle Size a nd Flow Rate on Measured Penetration through MSA N95 Filtering Facepiece at Constant Flow

0.01

0.1

1 10 100

0.01 0.1 1 10 

### Particle Size ( μ m)Penetration (%) 40 L/min [MIF = 85 L/min] 85 L/min [PIF = 270 L/min] 115 L/min [PIF = 360 L/min]

Figure 24. Effect of Particle Size a nd Flow Rate on Measured Penetration through MSA N95 Filtering Facepiece at Cyclic Flow41 3.5.2 Constant/Cyclic Flow Comparisons

An important aspect of this task was to co mpare penetrations measured under constant and cyclic flow conditions. NIOSH certification te sting of particulate filters is performed at a constant flow rate of 85 L/min (42 CFR 84, 1995 ) to demonstrate that filters meet a minimum requirement under controlled labor atory conditions. However, m easurements of physiological parameters of workers show peak inhalation flow rates in excess of 300 L/ min for short durations during high work load activities (Caretti et al., 2004; Kauf man and Hastings, 2005). As described in Section 2.1, few studies have been completed to correlate performance measured under constant and cyclic flow. Thus, there is concern that cu rrent certification test flow conditions may underestimate perfor mance under actual use conditions. The cyclic and constant flow conditions for th is task were selected to allow comparisons based on cyclic flow: (1) minute volume, (2) MIF, and (3) PIF. Recall, the MIF is the average flow rate over the inhalation por tion of the breathing cycle and the PIF is the maximum flow rate
obtained. The flow conditions used to make th ese comparisons where noted in Table 3. For example, the 85 L/min constant flow matches a cy clic flow minute volume (2.3 L tidal volume, 37 breaths/min) and a MIF (1.6 L tidal volume, 25 breaths/min). Figure 25 compares the penetrations meas ured under 85 L/min cyclic (based on minute volume) and constant flows. Although not explic itly shown, the data points correspond to the measured penetrations over the range of particle sizes tested (i.e., 0.02 to 2.9 μ m). The black line is the 1-to-1 line and represents perfect agreement between the penetrations measured under
the different flow conditions. The red and blue solid lines represent the best fit regressions of the cartridge and filtering facepiece data, respectiv ely. The dashed lines represent 95 percent confidence intervals. The regre ssion lines are both above the 1-to -1 line by a factor of 5 to 10 indicating higher penetrations we re measured under cyclic flow for a given minute volume or
constant flow of 85 L/ min . The regressions for the cartridges and filtering facepieces were nearly identical indicating that the trend is not dependent on filter type (i.e., cartridge versus filtering facepiece). Higher penetr ations under cyclic flow were exp ected and are in agreement with the literature (Brosseau et al., 1990). For the sinusoi dal flow used in this task (2.3 L and 37 breaths/min), over 95 percent of the inhalation volu me passes through the filter at a rate in excess42 of the minute volume. The peak flow reaches 2 70 L/min. As discussed above, penetration tends
to increase with increased flow rate.

Constant Flow Average Penetration (%) 0.0001 0.001 0.01 0.1 1 10 100Cyclic FlowAverage Penetration (%)

0.0001 0.001

0.01 0.1

1 10 100

Cartridge Data Cartridge Regression 95% Confidence Interval 1:1 Line Filtering Facepiece Data Filtering Facepiece Regression 95% Confidence Interval

Figure 25. Comparison of Measured Penetr ations under Cyclic and Constant Flow Conditions with Minute Volumes of 85 L/min
Figure 26 and 27 compare the measured pene trations under constant flow with those measured under cyclic flow with an equivalent MIF or PIF for the car tridges and filtering facepieces, respectively. The tre nds were nearly identical for bot h filter types. The MIF data points tend to lie above the 1-to-1 line indicating the penetrations measured under constant flow equivalent to the MIF were lower (40 percent lower on average) than the corresponding cyclic flow penetration. The converse was observed for the PIF comparis on indicating that testing at a constant flow equivalent to th e PIF provides a conservative estim ate of filter performance under cyclic flow. The regression line for the PIF co mparison nears the 1-to-1 line at the higher penetrations (>1%) where the data is for the N95 filters. Thus, it may be more important to consider the PIF when testing N95 filters, especially at the high volumetric flow rates that can be experienced during heavy work loads. As stat ed earlier, the N95 cartr idges and both types of filtering facepieces are not well-suited for the hi gh flow rates due their lower surface area as compared to the P100 cartridge filters evaluated in this study. A simila r plot containing only P100 cartridge data is provided in Figure 28. Good agreement (w ithin a factor of two) is
observed between the constant flow penetrations and those measured at a cyclic flow with an43 equivalent MIF. A method to es timate the cyclic flow penetrat ion based on measured constant flow is provided in Appendix F. Good agreemen t is shown between the predicted and measured cyclic flow penetrations from this study.

Constant Flow Average Penetration (%) 0.0001 0.001 0.01 0.1 1 10 100Cyclic FlowAverage Penetration (%)

0.0001 0.001 0.01 0.1

1 10 100

MIF Regression 95% Confidence Interval PIF Regression 95% Confidence Interval North N95 [MIF] MSA N95 [MIF] SEA P100 [MIF] Survivair P100 [MIF] North N95 [PIF] MSA N95 [PIF] SEA P100 [PIF] Survivair P100 [PIF]

985

. 0 ; 15

. 0 ] [ log 1

. 1 ] [ log : 964

. 0 ; 20

. 0 ] [ log 98

. 0 ] [ log :

2 10 10 2 10 10

= − × = = + × =

r P P PIF r P P MIF

Const Cyclic Const Cyclic

Figure 26. Comparison of Penetrations Measured under Constant and Cyclic Flow Conditions for Cartridge Filters

Constant Flow Average Penetration (%) 0.0001 0.001 0.01 0.1 1 10 100Cyclic FlowAverage Penetration (%)

0.0001 0.001

0.01

0.1

1 10 100

MIF Regression 95% Confidence Interval PIF Regression 95% Confidence Interval MSA N95 [MIF] Gerson N95 [MIF] 3M P100 [MIF] Moldex P100 [MIF] MSA N95 [PIF] Gerson N95 [PIF] 3M P100 [PIF] Moldex P100 [PIF]

947

. 0 ; 10

. 0 ] [ log 2

. 1 ] [ log : 944

. 0 ; 17

. 0 ] [ log 95

. 0 ] [ log :

2 10 10 2 10 10

= − × = = + × =

r P P PIF r P P MIF

Const Cyclic Const Cyclic

Figure 27. Comparison of Penetrations Measured under Constant and Cyclic Flow Conditions for Filtering Facepieces44 Constant Flow Average Penetration (%) 0.0001 0.001 0.01 0.1 1Cyclic FlowAverage Penetration (%)

0.0001 0.001

0.01

0.1

1

MIF Regression 95% Confidence Interval PIF Regression 95% Confidence Interval SEA P100 [MIF] Survivair P100 [MIF] SEA P100 [PIF] Survivair P100 [PIF]

947

. 0 ; 42

. 0 ] [ log 96

. 0 ] [ log : 923

. 0 ; 04

. 0 ] [ log 96

. 0 ] [ log :

2 10 10 2 10 10

= − × = = + × =

r P P PIF r P P MIF

Const Cyclic Const Cyclic

Figure 28. Comparison of Penetrations Measured under Constant and Cyclic Flow Conditions for P100 Cartridge Filters

3.6 Inert Aerosol Testing Summary

Filter efficiency testing was completed to assess the effect of particle size and flow condition on measured penetration. The following trends were observed:

• Penetration of submicron part icles tended to increase with increased volumetric flow rate. The magnitude of increase was dependent on the filter type and particle size.

• The MPPS for P100 cartridges was generally between 0.1 to 0.2 μ m and shifted toward the lower end of this range with increased flow.

• The MPPS for the N95 cartridges was generally 0.05 to 0.1 μ m for all flow conditions.

• The MPPS for both P100 and N95 filtering facepieces was 0.05 to 0.1 μ m.

• All filters efficiently removed the 0.7, 1.3, and 2.9 μ m particles. Penetrations through
P100 and N95 filters were less than 0.03 and 5 percent respectively, at all flow conditions and, thus, met the NIOSH requirement.

• Penetrations of submicron particles were in excess of the NIOSH requirements under the high flow conditions for all filters except the SEA HE-T P100 cartridge. The45 Assigned Protection Factor (APF) of the ma sk and workplace breathing rates must be
taken into account to determine if the increase in penetra tion is significant.

The following trends were observed regardi ng the comparison of penetrations measured under constant and cyclic flow conditions:

• Higher penetrations were measured under cy clic flow conditions as compared to a constant flow with an equivalent minute volume.

• Testing at a constant flow e quivalent to the cyclic flow PIF provided a conservative estimate of filter performa nce under cyclic conditions.

• For the P100 cartridges, penetrations meas ured under constant flow and cyclic flow with an equivalent MIF were within a factor of two.

4.0 BIOAEROSOL FILTRAT ION EFFICIENCY TESTING

NIOSH-approved N, R, and P se ries particulate respirator fi lters have been shown to be effective against inert test aeros ols in the most penetrating size range. However, it has not been well established that these filters provide comp arable protection against biological aerosols especially with regard to high br eather flow rates. This section describes the test methods and
matrices that were used to characterize th e performance of NIOS H-approved N95 and P100 filters using bacterial and viral aerosols under hi gh breathing flows. The flow conditions and filter types were the same as described in Sec tion 3.0 to allow direct comparison to the inert aerosol results. The two primar y objectives were to: (1) assess respirator performance against bioaerosols, both bacterial and viral, under high flow conditions and (2) compare the measured aerosol penetrations to those of the inert aerosols.

4.1 Test Parameters

The filters tested included two N95 filte ring facepieces, two P100 filtering facepieces, two N95 cartridges, and two P100 cartridges. They were the same brands and models as described in Table 2 of Section 3.1 and once agai n the exhalation valves were not sealed. The environmental conditions during testing were main tained at ambient temp erature (25 ± 3°C) and46 relative humidity (40 ± 10%). The filters were not preconditioned prior to te sting (i.e., tested asreceived). Tests were performed at two cyclic and two constant flow ra tes. The cyclic flow
conditions had minute volumes of 85 and 135 L/min. Refer to Table 4 for the tidal volumes and breathing rates. The constant flow rates were 85 and 270 L/min. The 85 L/min was selected as
it is the NIOSH certification flow rate. The 270 L/min provided an equivalent PIF and MIF to the cyclic flow conditions. Again, cartridges were tested at half the flow rate. The biological aerosols cons isted of bacterial Bg spores and viral MS2 phage. Both were generated using two differe nt methods referred to as "w et" and "dry". Wet denotes dispersion of organisms in an effort such that the primary organism is achieved from a liquid suspension using a nebulizer. Dry denotes generation from a powder with a special carrier material or as agglomerates. Preparation a nd aerosol generation methods are described in Section 4.3. Bg spores were sel ected as the test aerosol due to th eir robustness. Thus, they have a high probability of remaining viable during the test. Bg spores are also a simulant commonly used for anthrax spores. Bg spores are rod-shap ed with an approximate diameter of 0.7 to 0.8

μ m and a length of 1.5 to 1.8 μ m (Johnson et al., 1994). The aerodyna mic diameter is typically
0.8 to 1.0 μ m when suspended in water and aerosolized using a collison ne bulizer (McCullough et al., 1997; Hanley and Foarde, 2003; Hofacre and Forney, 1996). MS2 was selected as a representative viral aerosol as its viability after aerosolization has been demonstrated in a pr evious study (Hofacre et al., 1996) . Viruses range in size from
0.02 to 0.3 μ m and are generally found airbor ne as part of a droplet nuc lei or attached to inert particles (Hinds, 1999). MS2 phage is icosahed ron-shaped measuring approximately 20 nm in diameter. It is a bacteriophage that replicates inside host E. coli cells. Bacteriophages are nonpathogenic to humans and thus are safe to use fo r testing with limited engi neering controls. As described earlier, Hofacre et al. (1996) aer osolized MS2 phage using a three-jet Collison nebulizer and measured the particle size dist ribution using a high-sens itivity laser aerosol spectrometer (HS-LAS, Particle Measuring System s, Boulder, CO). The MS2 was present over a wide range of particle sizes likely as a ggregates. The number distribution mode was approximately 0.1 μ m and the mass distribution mode was 0.3 to 0.4 μ m. The bioaerosol challenge concentration wa s dependent on the target particle size and generation method. During charac terization, suitable operating para meters were determined to permit measurement of aerosol penetrations of at least 0.03 per cent, the NIOSH P10047 requirement. Estimates of the minimum meas urable penetration were made based on the challenge concentration, downs tream sampling duration, and minimum detection limit of the aerosol sensing instrument. The minimum meas urable penetration was generally 0.003, an order-of-magnitude lower than the NIOSH P100 requirement.

4.2 Test Matrix

The test matrices completed with the bioaer osol challenges are pr ovided in Tables 8 and 9 for cyclic and constant flows, respectively. Three replicates were completed for each cell in the test matrix with the exception of the MS 2 "dry" testing where only two replicates were performed due to the high efficiency of the filters. Each test included measurement of the aerosol penetration using both a bioassay method for viable orga nisms and an aerosol sensing instrument to measure total particle penetration.

Table 8. Test Matrix Completed to Assess Filter Performance under Cyclic Flow Conditions Using a Bioaerosol Challenge
Filtering Facepiece Cartridges Minute Volume (L/min) Challenge Aerosol MSA N95 Gerson N95 3M P100 Moldex P100 North N95 MSA N95 SEA P100 Survivair P100 Bg "wet" 3 3 3 3 3 3 3 3 Bg "dry" 3 3 3 3 3 3 3 3 MS2 "wet" 3 3 3 3 3 3 3 3 85 (a) MS2 "dry" 2 2 2 2 2 2 2 2 Bg "wet" 3 3 3 3 3 3 3 3 Bg "dry" 3 3 3 3 3 3 3 3 MS2 "wet" 3 3 3 3 3 3 3 3 135 (a) MS2 "dry" 2 2 2 2 2 2 2 2 (a) Cartridges were tested at half the minute volume.
Table 9. Test Matrix Completed to Assess Filter Performance under Constant Flow Using a Bioaerosol Challenge
Filtering Facepiece Cartridges Flow Rate (L/min) Challenge Aerosol MSA N95 Gerson N95 3M P100 Moldex P100 North N95 MSA N95 SEA P100 Survivair P100 Bg "wet" 3 3 3 3 3 3 3 3 Bg "dry" 3 3 3 3 3 3 3 3 MS2 "wet" 3 3 3 3 3 3 3 3 85 (a) MS2 "dry" 2 2 2 2 2 2 2 2 Bg "wet" 3 3 3 3 3 3 3 3 Bg "dry" 3 3 3 3 3 3 3 3 MS2 "wet" 3 3 3 3 3 3 3 3 270 (a) MS2 "dry" 2 2 2 2 2 2 2 2 (a) Cartrdiges were tested at half the flow rate.48 4.3 Technical Approach

4.3.1 Test System

The test system used for biol ogical testing was very similar to that used at ECBC for the inert testing with the large particle challenges (i.e., 0.7 to 2.9 μ m). The test system, illustrated in Figure 29 for generating with a ne bulizer, included an aerosol ge nerator, exposure chamber with filter holder, aerosol classifier/sampler, and breathing machine. The aerosol generation and sampling systems varied depending on the biologi cal aerosol being genera ted and are described
in Sections 4.3.2 and 4.3.3.

Figure 29. Schematic of Test System Used to Measure Bioaerosol Penetration

The aerosol generation systems delivered a co ntinuous flow of aeros ol laden air to the chamber to ensure a fresh, stable challenge aer osol was maintained. The challenge laden air exiting the generator was mixed with HEPA filtere d dilution air. When generating from a liquid49 solution, this mixing promoted the drying of the aerosol. The aerosol was then passed through a charge neutralizer (Model 3012, TSI, Shorevie w, MN) and introduced in to the test chamber where it was dispersed by small mixing fans. Excess challenge was vented through a HEPA
filter and exhausted into the hood. The HEPA filters also allowe d additional dilution air to be pulled into the chamber upon demand. The mask filter (filtering facepie ce or cartridge) was
mounted onto a holder and sealed inside the chamber. The holder was connected to the breathing machine (cyclic flow) or vacuum pump (constant flow) by flexible tubing. Similar to the approach used at ECBC for the inert testi ng, the downstream aerosol was sampled from a small chamber equipped with a stainless steel sample probe. The downstream chamber was also fitted with a port for sampling with the aerosol sensing instruments.

4.3.2 Bioerosol Generation Methods

Biological aerosols were generated using tw o different methods: (1) from an aqueous solution and (2) from a dry powder. This sec tion describes both of these aerosol generation methods. For details regarding the preparation of the Bg spores and MS2 phage, refer to Appendix G.

4.3.2.1 Wet. The aerosol generation system for the wet technique consisted of a nebulizer, dryer, and charge neutralizer. The Bg spores or MS2 were suspended in filtered, deionized water and aerosolized using a 24- jet Collison nebulizer. Typical suspension
concentrations were 1 x 10 8 colony forming units (cfu)/ml for the Bg spores and 1 x 10 11 plaque forming units (pfu)/ml for MS2 phage. The aeros ol was diluted with filtered house air and then pass through a Kr-85 charge neutralizer (Model 3 012, TSI, Shoreview, MN) prior to delivery to the test chamber. Typical viable challenge concentrations were 1 x 10 5 cfu or pfu/L air. The charge neutralizer had to be removed from the test system when challenged with MS2 "wet" to obtain the target concentration.

4.3.2.2 Dry. The preparation of the dry powders is described in Appendix G. The dry powders were aerosolized us ing the Vilnius Aerosol Gene rator (VAG, CH Technologies, Westwood, NJ) shown in Figure 30. The VAG c onsists of three primary components:50 (1) disperser, (2) aerosol mon itor, and (3) output controller. The dry powder is placed on a membrane in the aerosolization chamber. Compre ssed air is used to vibrate the membrane to aerosolize the powder and also activate a rotary turbovane wh ich deaglommerates the particles.
The aerosolization chamber and tu rbovane are shown in Figure 31. The Microdust 880 (Casella, Bedford, UK) is used to conti nuously monitor the aerosol output. The controller processes the signal from the Microdust 880 and ad justs the frequency of vibrati on to maintain a steady aerosol output. Typical viable aerosol conc entrations were generally 1 x 10 4 to 1 x 10 5 cfu or pfu/L air.

Figure 30. Vilnius Aerosol Generator51 Figure 31. Aerosolization Chamber and Rota ry Vane of Vilnius Aerosol Generator

4.3.3 Aerosol Sampling and Classification

Samples to assess penetration of viable organisms were collected on 47-mm filters as described in Section 4.3.3.1. In addition, two ty pes of light scattering in struments, described in
Section 4.3.3.2 were used to meas ure total-particle efficiencies.

4.3.3.1 Viable Samples. Viable samples were collected on 47-mm filters for subsequent bioassay. Bg spores were collected on mixed cellulose es ter filters and the MS2 phage was collected on water soluble gelatin filters. The mixed cellulose ester filters were not used with the MS2 due to poor collection efficiency at the smaller particle size. The challenge sample was collected through a sa mpling probe that extended away from the chamber wall. The
47-mm filter was housed in a 47 mm filter holder and a sample pump was used to pull 4 L/min through the filter. A critical orif ice was used to control the flow rate. The filters were analyzed as described in Appendix G to determine the num ber of colony forming units (cfu) or plaque forming units (pfu) per liter of air sampled.52 4.3.3.2 Optical Particle Counters. The Aerosizer ® (Amherst Proscess Instruments, Hadley, MA) classifies particle s based on their aerodynamic behavi or. The instrument measures the time-of-flight as particles are accelerated th rough the sensing zone of the instrument. The time-of-flight is proporti onal to particle size and density. The density of the aerosol material is used to determine the particle size distribution either on a number, surface, or volume (mass)
basis. The Aerosizer ® can classify particles ranging from 0.5 to 200 μ m. Data reducing software that accompanies the instrument permits user selected size ranges to be analyzed. Thus, polydisperse aerosols could be anal yzed within a selected size range. The sample flow rate is
1.5 L/min. The laser aerosol spectrometer (LAS-X, Par ticle Measuring Systems, Boulder, CO) is a laser aerosol spectrometer capable of cl assifying particles between 0.1 and 3.0 μ m in diameter
into 16 size discrete bins. Th e LAS provides a measure of the particle size based on the light scattering properties of the aerosol. Particle s are focused into the sensing region by the pneumatic system such that par ticles pass through one at a time. The light from the He-Ne laser is scattered by the particle, which is then collected by receiving optics. The signal intensity produced is proportional to the particle size a nd the number of signals is a measure of the number of particles counted. Thus, the LAS gives a number dist ribution of the aerosol and size specific channels of interest which can be selected for data analysis. The sample flow rate is approximately 100 cm 3 /min.

4.3.3.3. Cascade Impactor. A cascade impactor (Model 266 Marple Impactor, Sierra Instruments, Carmel Valley, CA) was used to characterize the aer odynamic particle size distribution of the viable biological aerosols. The impactor was ope rated at 2.4 L/min. Particles
of sufficient size and inertia cross the flow str eamline and are impacted on slides and collected. Smaller particles are able to remain in the flow streamlines and pass on to the next stage. Each stage has an associated diameter cut-point equivalent to particle size (diameter). A calculation of the loaded mass of the impactor slide and the volumetric flow rate, in conjunction with volumedensity relationship, reveals the number of particles with a given size bin. Characteristics of the impactor are listed in Table 10 with ranges of aerodynamic particle diameters highlighted. The number of viable particles collected on each stage was determined by bioassay.53 Table 10. Particle Size Range Six-Stage Cascade Impactor Impactor Stage Aerodynamic Diameter Range ( μ m)

Backup filter d ≤ 0.29 Stage 1R 0.29 < d ≤ 0.78 Stage 6 0.78 < d ≤ 1.5 Stage 5 1.5 < d ≤ 3.2 Stage 4 3.2 < d ≤ 6.8 Stage 3 6.8 < d ≤ 12 Stage 2 12 < d ≤ 19 Stage 1 d > 19

4.3.4 System Characterization

Prior to efficiency testing, shakedown testing was performed to establish proper operating conditions. This included comparison of the Battelle and ECBC test systems, characterization of the aerosol ge nerators, measurement of bioaeros ol particle size distributions, and characterization of the viable particle samp lers. The shakedown testing is described in Appendix H.

4.3.5 Test Procedure

The mask filter was mounted to the test fixture and the exposure chamber sealed. The breathing machine and bioaerosol generation system were starte d and allowed to operate for approximately 10 minutes to reach a steady state challenge concentration. The mask filter and downstream bioaerosol sampler were bypassed duri ng system startup. After approximately 10 minutes, sampling with the viable particle samp lers began by directi ng the flow through the mask filter. The upstream and downstream 47-mm filters were collected simultaneously. Sample duration depended on the expected aeroso l concentration and was typically 2 minutes for the challenge aerosol and 10 minutes for the do wnstream. Two sets of 47 mm filters were collected in sequence. The average measured concentrations were used to determine the penetration. Sampling with the HS-LAS or Aerosizer ® was performed simu ltaneously with the viable particle samplers. First, the challeng e was sampled for approximately two minutes. The sampling line was then switched to downstream of the filter and adequate time was given for the54 instrument response to stabilize. The downstrea m sample duration ranged from five to fifteen minutes to provide sufficient time to count a st atistically significant num ber of particles. A second sample of the challenge was then recorded. If the tw o challenge samples (before and after downstream sampling) were not within 20 pe rcent of each other, the test was repeated. After sampling was complete, the aerosol ge neration system was stopped and the chamber flushed with clean air. The viable particle sa mplers were removed from the test system for analysis.

4.4 Calculation of Aerosol Penetration

The aerosol penetration was de fined in Section 3.4 for the inert aerosols. Efficiencies were measured based on both total and viable part icle concentrations. For the total particle analyzers, the size specific channels of interest were selected for the analysis. The challenge concentration was the average of the measurem ents made before and after the downstream sample. The aerosol number concentration us ed was determined by summing the number of particles in the selected size range and dividi ng by the volume of air sampled (product of sampling flow rate and sampling duration). The viable particle concentration was determined from the bioassay of the 47-mm filters. Two upstream and two downstream samples were collected during each test. The number of partic les, after correcting for dilution factors during bioassay, was divided by the volume of air samp led to obtain the number concentration. The average values were used to calculate the penetration. As described in Section 4.1, the challenge concentration was maintained at a level to measure penetrations of at leas t 0.03 percent. Minimum detec tion limits were established for both the Bg spore and MS2 phage enumeration me thods. The limits were 2 cfu or pfu/L air sampled. The typical challenge concentr ation for the Bg spore testing was 1 x 10 5 cfu/L resulting in a minimum measurable penetration of 0.002 percent. Likewise, depending on flow condition, the challenge concentratio n of MS2 phage ranged between 1 x 10 4 and 1 x10 5 leading to minimum penetrations of 0.02 to 0.002 percent. The actual minimum penetration varied from trial to trial depending on the m easured challenge concentration.55 4.5 Bioaerosol Results

This section summarizes the results of tes ting with biological aeros ols. Section 4.5.1 discusses the measured Bg spore particle size di stributions and the meas ured penetrations. A
similar discussion follows in Section 4.5.2 fo r the MS2 phage. Section 4.5.3 compares the penetrations measured using the biological aerosols to those meas ured with the inert aerosols.

4.5.1 Bg Spore Results

4.5.1.1. Particle Size Distribution. The aerosol size distributi ons of the Bg spores generated using the "wet" and "d ry" methods were characterized using the cascade impactor and
Aerosizer. The results are summarized in Tabl e 11 and are compared graphically in Figures 32 through 34 as measured by the impactor and Aero sizer. Note that the lower limit for the
Aerosizer is 0.5 μ m. Both instruments indicated that ae rosolization from the dry powder led to a slightly larger median diameter and broader dist ribution. The particle size distributions were
consistent with the literature which indicated an aerodynamic diameter ranging from 0.8 to 1.0

μ m (McCullough et al., 1997; Hanley and Foarde, 2003; Hofacre and Forney, 1996).

Table 11. Comparison of "Wet" a nd "Dry" Bg Size Distributions Aerosizer Impactor Generation

Method NMD ( μ m) σ g (a) AMMD ( μ m) σ g Bg "wet" 1.1 1.1 0.7 2.5 Bg "dry" 1.3 1.6 0.9 2.7 (a) σ g = Geometric standard deviation.56 Aerodynamic Diameter, μ m 1 2 3 4 5 6 7 8 910 20 0.5Probability

1 10 16 50 84 90 99

70 95

30

5 Bg "Wet" Bg "Wet" Regression Bg "Dry" Bg "Dry" Regression

Figure 32. Size Distribution of "W et" and "Dry" Bg Spores Measured Using the Cascade Impactor

0 500 1000 1500 2000 2500 3000 3500 4000

0.1 1 10 Particle Diameter (um)Number Concentration (#/cc)

Bg (Wet) Bg (Dry)

Figure 33. Size Distribution of Bg Spores Measured Using the Aerosizer57 Aerodynamic Diameter, μ m 1 2 3 4 5 6 7 8 9 10 0.5Probability

1 10 16 50 84 90 99

70 95

30

5 Bg "wet" Bg "dry"

Figure 34. Size Distribution of Bg Spores Measured Using the Aerosizer (Cumulative Number Distribution)

4.5.1.2 Bioassay Penetration Results. The penetrations measured using the Bg spore aerosol challenge and bioassay me thod are summarized in Tables 12 and 13 for the "wet" and "dry" generation techniques. The penetrations ge nerally represent the aver age of at least three trials. Average penetrations with at least one trial below the minimum detection limit (~0.002%)
are noted and standard deviations are not provided. The results from the individual trials are summarized in Appendix I. Both the P100 cartridge s and filtering facepieces were very efficient against the Bg spore challenge as all penetrations were less than the 0.03 percent requirement, generally by at least an order-of-magnitude. The N95 filters were less efficient as compared to the P100 filters but still had penetr ations generally less than 0.5 per cent. As shown in Figures 35 and 36, the penetrations increased with increased flow rate with exception of the MSA Affinity
Plus ® filtering facepiece and the "wet" Bg challe nge. The cause of this anomaly was not identified and repeated tests provided similar re sults. This trend was not observed for the Bg "dry" aerosol.58 Table 12. Comparison of Penetration Measured Using Bioassay Method and Bg Spore "Wet" Aerosol Challenge under Constant and Cyclic Flow Conditions

Flow Rate (a) (L/min) Constant Cyclic 85 270 85 135 Filter Type Filter Average Penetration (%) MSA N95 0.002 (b) 0.005±0.001 0.003 (b) 0.034±0.041 North N95 0.005 0.009 (b) 0.006±0.004 0.014±0.007 Survivair ® P100 0.003 (b) 0.004 (b) 0.001 (b) 0.006 (b) Cartridge

SEA P100 0.004 (b) 0.004 (b) 0.002 (b) 0.002 (b) MSA N95 0.13±0.12 0.13±0.10 0.35±0.18 0.047±0.024 Gerson ® N95 0.036±0.23 0.40±0.18 0.21±0.08 0.26±0.07 3M ® P100 0.003 (b) 0.010 (b) 0.005 (b) 0.005 (b) Filtering Facepiece Moldex P100 0.023 (b) 0.012 (b) 0.006±0.002 0.009±0.002 (a) Cartridge testing performed at half the flow rate (b) At least one trial resulted in penetration below detectable limit

Table 13. Comparison of Penetration Measured Using Bioassay Method and Bg Spore "Dry" Aerosol Challenge under Constant and Cyclic Flow Conditions

Flow Rate (a) (L/min) Constant Cyclic 85 270 85 135 Filter Type Filter Average Penetration (%) MSA N95 0.005 (b) 0.014±0.004 0.013±0.002 0.030±0.011 North N95 0.006±0.005 0.074±0.075 0.055±0.047 0.032±0.001 Survivair ® P100 0.003 (b) 0.030 (b) 0.002 (b) 0.003 (b) Cartridge

SEA P100 0.001 (b) 0.003 (b) 0.003 (b) 0.002 (b) MSA N95 0.035±0.030 0.042±0.016 0.13±0.048 0.64±0.59 Gerson ® N95 0.028±0.007 0.20±0.064 0.20±0.14 2.4±2.5 3M ® P100 0.008 (b) 0.03 (b) 0.001 (b) 0.003 (b) Filtering Facepiece Moldex P100 0.017±0.015 0.004 (b) 0.003 (b) 0.003 (b) (a) Cartridge testing performed at half flow rate (b) At least one trial resulted in penetration below detectable limit59 0.001

0.01

0.1

1 10

MSA Flexi-Filter (Cartridge) North 7506 (Cartridge) MSA Affinity Plus (Filtering Facepiece) Gerson 1730 (Filtering Facepiece)Penetration (%) 85 L/min (constant) 270 L/min (constant) 85 L/min (cyclic) 135 L/min (cyclic)

Figure 35. Comparison of Measured Bg "Wet" Penetrations through N95 Filters

0.001

0.01

0.1

1 10

MSA Flexi-Filter (Cartridge) North 7506 (Cartridge) MSA Affinity Plus (Filtering Facepiece) Gerson 1730 (Filtering Facepiece)Penetration (%) 85 L/min (constant) 270 L/min (constant) 85 L/min (cyclic) 135 L/min ( cyclic)

Figure 36. Comparison of Measured Bg "D ry" Penetrations through N95 Filters

The penetrations measured using the "wet" and "dry" Bg challenges with the bioassay method are compared in Figures 37 and 38 fo r the cartridges and filtering facepieces, respectively. The black diagonal line is the 1-to-1 lin e and represents perfect agreement. The60 error bars represent one standa rd deviation about the mean. In general, the penetrations measured with each challenge for each filter were within a factor of four. From a practical perspective, the differences in the penetrations were not significant.

0.0001

0.001

0.01

0.1

1 10

0.0001 0.001 0.01 0.1 1 10 Bg "Wet" Penetration (%)Bg "Dry" Penetration (%)

MSA N95 North N95 SEA P100 Survivair P100

Figure 37. Comparison of Bg "Wet" and "Dry " Penetrations through Cartridge Filters

0.0001

0.001

0.01

0.1

1 10

0.0001 0.001 0.01 0.1 1 10 Bg "Wet" Penetration (%)Bg "Dry" Penetration (%)

Gerson N95 MSA N95 Moldex P100 3M P100

Figure 38. Comparison of Bg "Wet" and "Dry " Penetrations through Filtering Facepieces61 Figure 39 compares the penetrations measur ed using the bioassay method with that using the LAS-X. Again, the black diagonal line represents the 1-to-1 lin e. During each trial, the penetration was measured usi ng both techniques creating paired data. For the LAS-X, the penetration was calculated ba sed on size specific channels ranging from 0.65 to 1.25 μ m (Channels 9, 10, and 11). The results from each trial are plotted in Figure 39. Higher penetrations tended to be measured using th e LAS as compared to the bioassay method as evidenced by the majority of the data points lyin g below the 1-to-1 line. This is likely because the LAS measured total pa rticle penetration while the bioassa y method measured only the viable particle penetration. These results demonstrate that using an optical li ght scattering instrument such as the LAS to measure bacterial aerosol pe netration provides a conservative estimate of filter performance. This conclusion is consistent with the literature (Brosseau et al., 1994) and is
notable since the LAS-X method is much less labor intensive comp ared to the bioassay method.

Penetration, LAS-X (%) 0.0001 0.001 0.01 0.1 1Penetration, Bioassay (%)

0.0001 0.001

0.01

0.1

1
"Wet" Bg Cartridges "Wet" Bg Filtering Facepieces "Dry" Bg Cartrdiges "Dry" Bg Filtering Facepieces

Figure 39. Comparison of Bg Spore Pene trations Measured Using the Bioassay Method and LAS-X62 4.5.2 MS2 Phage Results

4.5.2.1. Particle Size Distribution. The aerosol size distribu tions of the MS2 phage generated using the "wet" and "d ry" aerosolization met hods were characterized using the cascade impactor, LAS, and Aerosizer. The results ar e summarized in Table 14 and are compared graphically in Figures 40 thr ough 42. Note that the lower li mit for the Aerosizer is 0.5 μ m and
the LAS is 0.1 μ m.

Table 14. Comparison of "Wet" and "D ry" MS2 Aerosol Size Distributions LAS/Aerosizer Impactor Generation

Method NMD ( μ m) σ g AMMD ( μ m) σ g MS2 "wet" 0.2 (a) 1.4 0.5 1.3 MS2 "dry" 2.3 (b) 1.3 2.5 2.0 (a) Size distribution measur ed using LAS-X only. (b) Size distribution measured using Aerosizer only.

Aerodynamic Diameter, μ m 1 2 3 4 5 6 7 8 910 20 0.5Probability

1 10 16 50 84 90 99

70 95

30

5

Figure 40. Size Distribution of MS2 "W et" Measured Using the Sierra Impactor63 Figure 41. Size Distribution of MS 2 "Wet" Measured Using the LAS-X

Aerodynamic Diameter, μ m 1 2 3 4 5 6 7 8 910 20 0.5Probability

1 10 16 50 84 90 99

70 95

30

5 Cascade Impactor Aerosizer

Figure 42. Size Distribution of MS2 "Dry" Measured Using the Sierra Impactor and Aerosizer

4.5.2.2 MS2 Penetration Results. The penetrations meas ured using the MS2 phage aerosol challenge and bioassay me thod are summarized in Tables 15 and 16 for the "wet" and "dry" aerosol generation techniques . The results from the individua l trials are summarized in Appendix I. The P100 and N95 filters both met their respective penetration requirements (i.e., maximum 0.03 and 5 percent penetration) at all flow conditions tested. This is significant
because the MS2 "wet" aerosol is near the MPPS for both types of filters. As shown in Figure 43, mean penetration of the "wet " MS2 aerosol tended to increase with increased flow rate. All 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 Particle Diameter ( μ m)Δni/nTΔlog di64 filters were highly efficient at removing the MS2 "dry" aerosol challenge as expected since it had
a count median diameter above 1 μ m. Flow rate did not have as significant an effect on MS2 “dry” aerosol penetrations as with the smaller MS2 "wet" as shown in Figure 44. The P100 filters are not included in Figures 43 and 44 as the measured penetrations were generally below detectable limits. Assuming that inertial imp action is the primary mech anism for collection of the MS2 "dry" aerosol, penetration would not be e xpected to change significantly with increased
flow.

Table 15. Comparison of Penetration Measured Using Bioassay Method and MS2 "Wet" Aerosol Challenge under Constant and Cyclic Flow Conditions

Flow Rate (a) (L/min) Constant Cyclic 85 270 85 135 Filter Type Filter Average Penetration (%) MSA N95 0.55±0.75 1.3±1.2 1.1±1.0 0.54±0.36 North N95 0.30±0.10 1.9±1.1 1.7±2.0 2.5±1.7 Survivair ® P100 0.022±0.015 0.018 (b) 0.012 (b) 0.030 (b) Cartridge

SEA P100 0.002 (b) 0.009 (b) 0.007 (b) 0.015 (b) MSA N95 0.51±0.37 1.7±1.8 0.93±0.60 1.1±0.61 Gerson ® N95 0.51±0.30 1.8±0.55 0.48±0.07 0.89±0.43 3M ® P100 0.001 (b) 0.014 (b) 0.002 (b) 0.003 (b) Filtering Facepiece Moldex P100 0.005±0.003 0.050±0.007 0.001 (b) 0.010±0.006 (a) Cartridge testing performed at half the flow rate (b) At least one trial resulted in penetration below detectable limit

Table 16. Comparison of Penetration Measured Using Bioassay Method and MS2 "Dry" Aerosol Challenge under Constant and Cyclic Flow Conditions

Flow Rate (a) (L/min) Constant Cyclic 85 270 85 135 Filter Type Filter Average Penetration (%) MSA N95 0.009 (b) 0.007±0.004 0.003 (b) 0.025±0.005 North N95 0.001 (b) 0.022±0.001 0.005±0.002 0.012±0.009 Survivair ® P100 0.002 (b) 0.002 (b) 0.005 (b) 0.012 (b) Cartridge

SEA P100 0.001 (b) 0.002 (b) 0.001 (b) 0.004 (b) MSA N95 0.007 0.009±0.004 0.022±0.009 0.082±0.030 Gerson ® N95 0.22±0.27 0.52±0.69 0.60 0.075±0.034
3M ® P100 0.002 (b) 0.004 (b) 0.009 (b) 0.003 (b) Filtering Facepiece Moldex P100 0.004 (b) 0.004 (b) 0.014 (b) 0.004 (b) (a) Cartridge testing performed at half flow rate (b) At least one trial resulted in penetration below detectable limit65 0.1

1 10

MSA Flexi-Filter (Cartridge) North 7506 (Cartridge) MSA Affinity Plus (Filtering Facepiece) Gerson 1730 (Filtering Facepiece)Penetration (%) 85 L/min (constant) 270 L/min (constant) 85 L/min (cyclic) 135 L/min (cyclic)

Figure 43. Comparison of Measured MS2 "Wet" Penetrations through N95 Filters

0.001

0.01

0.1

1 10

MSA Flexi-Filter (Cartridge) North 7506 (Cartridge) MSA Affinity Plus (Filtering Facepiece) Gerson 1730 (Filtering Facepiece)Penetration (%) 85 L/min (constant) 270 L/min (constant) 85 L/min (cyclic) 135 L/min ( cyclic)

Figure 44. Comparison of Measured MS2 "D ry" Penetrations through N95 Filters

Figure 45 compares the penetrations measur ed using the bioassay method with that using the LAS-X for the MS2 "wet" aerosol cha llenge. The "dry" aerosol results are not66 included as the majority of the penetrations measured using the bioassay method were below detectable limts. For the LAS-X, the penetra tion was calculated based on size specific channels ranging from 0.13 to 0.25 μ m (Channels 2, 3, and 4). As observed for the Bg spores, higher penetrations tended to be measured using th e LAS as compared to the bioassay method.

Penetration, LAS-X (%) 0.0001 0.001 0.01 0.1 1Penetration, Bioassay (%)

0.0001 0.001 0.01 0.1

1
"Wet" MS2 Cartridges

Figure 45. Comparison of MS2 Phage Penetrations Measured Using the Bioassay Method and LAS-X

4.5.3 Inert Comparisons

This section compares the penetrations m easured using the biological aerosols with those measured using the inert aerosols as descri bed in Section 3.0. The Bg spore comparisons are provided in Section 4.5.4. 1 and the MS2 comparisons follow in Section 4.5.4.2. The comparisons were performed only on the N95 filters as they generally had measurable penetrations. The biological penetrations through the P100 filters were generally below
detectable limits.

4.5.3.1 Bg Spores. Figure 46 compares the "wet" and "dry" aerosol pene trations through the North 7506 cartridge with the 0.7 and 1.3 μ m PSL. As shown, similar penetrations were
measured with the 1.3 μ m PSL as with the Bg aeroso ls. The penetration of 0.7 μ m PSL was typically an order-of-magnitude higher. Figure 47 also demonstrates the agreement with a67 micron sized particle. The red and blue horizont al lines represent the average penetrations measured using the Bg challenge at 42.5 a nd 135 L/min constant flow, respectively. The
intersection of these lines with the inert results is an indication of the inert particle size that provides an equivalent penetrati on. For example, measured bioaerosol and inert penetrations intersect at a particle size of approximately 1.7 μ m for the North 7506 cartridge at a 135 L/min flow rate. This intersection is designated by th e blue circle. The Bg spores had an AMMD of approximately 1.2 μ m as measured by the Aerosizer. Sim ilar trends were observed for the other N95 filters in Figures 48 through 50. In most cases, the 1.3 μ m PSL provided the best agreement as inert and Bg penetrations were generally within a factor of five.

0.001

0.01

0.1

1 10

42.5 L/min Constant 135 L/min Constant 42.5 L/min Cyclic 68 L/min Cyclic
Flow ConditionPenetration (%) Bg "Wet" Bg "Dry" 0.7 um PSL 1.3 um PSL

Figure 46. Comparison of Bg Spore and Inert Penetrations through the North N95 7506 Cartridge68 0.00001 0.0001 0.001 0.01 0.1

1 10 100

0.01 0.1 1 10 Particle Size (um)Penetration (%)

Inert Data - 42.5 L/min Inert Data - 135 L/min Bg Penetration - 42.5 L/min Bg Penetration - 135 L/min

Figure 47. Comparison of Measured Inert a nd Bg Bioaerosol Penetrations through the North 7506 Cartridge at Constant Flows of 42.5 and 135 L/min

0.0001

0.001

0.01

0.1

1 10

42.5 L/min Constant 135 L/min Constant 42.5 L/min Cyclic 68 L/min Cyclic
Flow ConditionPenetration (%) Bg "Wet" Bg "Dry" 0.7 um PSL 1.3 um PSL

Figure 48. Comparison of Bg Spore a nd Inert Penetrations through the MSA N95 Flexi-Filter Cartridge69 0.01

0.1

1 10

85 L/min Constant 270 L/min Constant 85 L/min Cyclic 135 L/min Cyclic
Flow ConditionPenetration (%) Bg "Wet" Bg "Dry" 0.7 um PSL 1.3 um PSL

Figure 49. Comparison of Bg Spore and Inert Penetrations through the MSA N95 Affinity Plus Filtering Facepiece

0.01

0.1

1 10

85 L/min Constant 270 L/min Constant 85 L/min Cyclic 135 L/min Cyclic
Flow ConditionPenetration (%) Bg "Wet" Bg "Dry" 0.7 um PSL 1.3 um PSL

Figure 50. Comparison of Bg Spore and Inert Penetrations through the Gerson N95 1730 Filtering Facepiece

4.5.3.2 MS2 Phage. Similar comparisons are provided in Figures 51 through 54 for the MS2 phage aerosol and 0.1, 0.3, and 0.7 μ m PSL penetrations through the N95 filters. The comparisons are not as well-defined for the MS2 phage. For the N95 cartridges, penetrations of
0.1 and 0.3 μ m PSL were generally higher than that of the MS2 "wet" aerosol and, thus, would provide a conservative estimate of filter performa nce. Due to its sma ller size, the MS2 “wet”70 aerosol penetration tended to be slightly higher than the 0.7 μ m PSL. For the N95 filtering facepieces, the MS2 “wet” aerosol pe netrations tended to be lower than those measured with the 0.1, 0.3, and 0.7 μ m PSL. The penetration of the MS 2 “dry” aerosol was typically below
detectable limits. This was consistent with th e penetrations measured for an inert aerosol of similar size (i.e., 2.9 μm PSL).

0.1

1 10 100

42.5 L/min Constant 135 L/min Constant 42.5 L/min Cyclic 68 L/min Cyclic
Flow ConditionPenetration (%) MS2 "Wet" 0.1 um PSL 0.3 um PSL 0.7 um PSL

Figure 51. Comparison of MS2 "Wet" a nd Inert Penetrations through the North N95 7506 Cartridge

0.001

0.01

0.1

1 10 100

42.5 L/min Constant 135 L/min Constant 42.5 L/min Cyclic 68 L/min Cyclic
Flow ConditionPenetration (%) MS2 "Wet" 0.1 um PSL 0.3 um PSL 0.7 um PSL

Figure 52. Comparison of MS2 "Wet" and Inert Penetrations through the MSA N95 Flexi-Filter Cartridge71 0.1

1 10 100

85 L/min Constant 270 L/min Constant 85 L/min Cyclic 135 L/min Cyclic
Flow ConditionPenetration (%) MS2 "Wet" 0.1 um PSL 0.3 um PSL 0.7 um PSL

Figure 53. Comparison of MS2 "Wet" a nd Inert Penetrations through the MSA N95 Affinity Plus Filtering Facepiece

0.1

1 10 100

85 L/min Constant 270 L/min Constant 85 L/min Cyclic 135 L/min Cyclic
Flow ConditionPenetration (%) MS2 "Wet" 0.1 um PSL 0.3 um PSL 0.7 um PSL

Figure 54. Comparison of MS2 "Wet" a nd Inert Penetrations through the Gerson N95 1730 Filtering Facepiece

4.6 Summary

The performance of NIOSH-approved N95 and P100 respirator filters has been assessed against bioaerosol challenges under high volumetri c flow conditions. Mean penetrations were below the penetration requirements for the respective filter types (i.e., penetration less than 5 percent for N95 and less than 0.03 percent for P100 filters) under all flow conditions tested. Penetrations of Bg spores through the P100 filters were typically below detectable limits and, thus, had penetrations at leas t an order-of-magnitude below the P100 requirement. The N95 filters also were very efficient at removing the bacterial aerosol challenges as average penetrations were less than 0.5 percent. There were not significant differences in the72 penetrations measured using th e "wet" and "dry" Bg spore aerosolization methods. The most penetrating of the biological aer osols tested was the "wet" MS2 phage as the particle size was closest to the MPPS. Average penetrations thro ugh the N95 and P100 filters were less than 2 and 0.03 percent, respectively, under all flow conditions. An inert aerosol of similar aerodynamic diameter was shown to provide a reasonable estimate of performance against biological aerosols as measured penetrations were generally with in a factor of five. The Bg spore "wet" and "dry" aero sol penetrations agreed favorably with the 1.3 μ m PSL results. In magnitude, the MS2 "wet" pene trations through the cartridge s were typically between penetrations measured using the 0.3 and 0.7 μ m PSL. Comparisons were not made with the MS2 "dry" as penetrations were typically below detectab le limits. However, this is in agreement with the penetrations measured for the 2.9 μ m PSL. The results demonstrated that testing with inert particles in the MPPS range provides a conser vative estimate against the biological aerosols assessed in this study. Finally, the results dem onstrated that using an optical light scattering
instrument such as the LAS to measure bacter ial aerosol penetration provides a conservative estimate of filter performance. This is signifi cant due to the labor in tensive nature of the bioassay method.

5.0 REAEROSOLIZATION

Reaerosolization of biological agents from previously bio-contaminated filtering facepieces is a potential concern for emergenc y responders and health care workers. The objective of this subtask was to assess the sign ificance of reaero solization of biological aerosols during simulated coughing through loaded filtering f acepieces. The results were also compared to those measured using inert particle s of similar size to the bioaerosols.

5.1 Test Parameters

Particle reaerosolization from two brands of N95 filtering facepieces was assessed, the MSA Affinity Plus and the Gerson 1730 and 1740. Within each brand, tests were performed on filtering facepieces with and without exhalati on valves. The Gerson 1730 and 1740 models are identical with the exception that the1740 has an exhalation valve. The exhalation valves were73 not sealed during the loading or reaerosolizati on tests. The estimated surface areas of the
filtration media for each of the filtering facepieces are summarized in Table 17. The filtering facepeices were loaded at a cyc lic flow rate of 85 L/min (2.3 L tidal volume, 37 breaths/min). The filters were not preconditioned with humidif ied air prior to loading. The loading and reaerosolization tests were performed under ambien t laboratory temperature (25 ± 5°C) and the relative humidity was measured (40 ± 10%). Fluorescent PSL (Duke Scientific, Palo Alto, CA)
with nominal diameters of 0.8 and 2.2 μ m were used as the inert aerosol challenge. Four biological aerosols, the same as described in Sec tion 4.0, were used and included Bg "wet", Bg "dry", MS2 "wet", and MS2 "dry." One r eaersolization flow prof ile was assessed that represented a cough. This prof ile, shown in Figure 55, was pr ovided by ECBC and is based on measurements made during human subject testing. The peak fl ow rate was approximately 370 L/min which corresponded to a su perficial velocity of approximately 40 cm/s assuming that the flow is evenly distributed over the entire facepiece (~170 cm 2 ). The cough profile was repeated three times in succession during each reaersol ization test over a period of approximately 30
seconds.

Table 17. Estimated Surface Areas of N95 Filtering Facepieces Filtering Facepiece Surface Area (cm 2 ) MSA Affinity Plus 175 MSA Affinity Plus (w/exhalation valve) 160 Gerson 1730 170 Gerson 1740 (w/exhalation valve) 15074 0 50 100 150 200 250 300 350 400

0 0.1 0.2 0.3 0.4 0.5 0.6 Time (sec)Flow Rate (L/min)

Figure 55. Cough Profile for Reaersolization Testing

The target loading level was 1x10 4 particles/cm 2 based on modeling by Stuempfle et al. (2004) who estimated the respirable concentr ation-time profile in ventilated enclosures (buildings) immediately following an intentional bio-agent release. The model was used to estimate resuspension of respirable pathogens by human activity after delayed entry into a contaminated area. This represents a "worst case" scenario for user s of filtering facepiece respirators. Based on the model results and a ssuming a breathing rate of 40 L/min, an 8-hour exposure, and a filter surface area of approximately 200 cm 2 , a loading of 1x10 4 particles/cm 2 represents a threat-based level. A limited set of tests were performed with the 0.8 μ m inert
aerosol to assess the effect of hi gher particle loading. Tests were performed at loading levels of
1x10 5 and 1x10 6 particles/cm 2 with the MSA Affinity Plus. The loading of 1x10 5 particles/cm 2 is consistent with Qian et al. (1997a).

5.2 Test Matrix

The test matrix completed to assess the extent of reaerosolization from the N95 filtering facepieces is provided in Table 18. Factors investigated includ ed filter type, particle size, particle type, and loading level. The inert aerosol s selected for testing were fluorescent PSL with
nominal diameters of 0.8 and 2.2 μ m. The 0.8 μ m PSL had a similar diameter as the Bg spores
and the 2.2 μ m PSL had a similar diameter as the MS 2 phage aerosolized as a dry powder.75 Table 18. Test Matrix Completed to Assess Reaerosolization
Target Load = 1 x 10 4 1 x 10 5 1 x 10 6 Loading

Flow (L/min) Aerosol Gerson 1730 No Ex. Valve Gerson 1740 Ex. Valve MSA Affinity Plus No Ex. Valve MSA Affinity Plus

Ex. Valve MSA Affinity Plus No Ex. Valve MSA Affinity Plus No Ex. Valve Bg "wet" 3 2 2 3 0 0 Bg "dry" 1 1 0 0 0 0 MS2 "wet" 3 1 3 3 0 0 MS2 "dry" 3 3 0 0 0 0 0.8 μ m PSL 3 2 2 3 3 3 85 Cyclic

2.2 μ m PSL 3 3 0 0 0 0

5.3 Test Method

5.3.1 Test System Description

The test system used to load the filtering f acepieces with the inert or biological particles
was the same as described in Section 4.3.1. Th e bioaerosol generation sy stem was as described in Section 4.3.2. The inert aerosol challeng e was generated from aque ous suspension using a 6-jet Collison nebulizer. The flow from the nebulizer was diluted with filtered, house air and passed through a Kr-85 charge ne utralizer (Model 3012, TSI, Shor eview, MN). Samples of the challenge aerosol were collected on 47-mm filters to quantify the challenge concentration. The inert particles were collected on membrane filters (Type HA, Millipore, Bedford, MA) with a rated pore size of 0.45 μ m. Membrane filters were used such that the particles would be
collected on the surface of the filte r and not embedded within the fibers. This was important as a counting method using a fluorescent microscope was used to quan tify the number of particles collected. The bioaerosol samples were collected on either mixed cellulose ester or water-soluble filters for subsequent bioassay. A separate test system, illustrated in Figure 56, was used to measure the percent reaersolization. It consisted of the breathing m achine, filtering facepeice holder, reaerosolization chamber, and aerosol sampling/classification syst em. The breathing machine used to simulate the cough was connected to the filter holder using 2. 5-cm OD flexible tubing. The inlet air to the breathing machine was HEPA filtered such that th e exhaled air was particulate free. The holder for the filtering facepiece consisted of a flat plat e with a 7.5 cm hole centr ally located to permit76 airflow. This plate was welded onto a cone that allowed the flow from the breathing machine to expand and distribute over the entire area of the filter. The filter holder sealed to the top of the reaerosolization chamber. The chamber was cylindr ical with a 0.7 m diameter and 0.6 m height. The bottom of the chamber tapere d down to the 47-mm collection filt er. The internal volume of the chamber was approximately 300 L. A vacuum pump was used to pull a continuous, constant flow through the chamber and collection filter. Make-up air was drawn through the HEPA filters located at the top of the chamber as needed.

MFM
Carbon Filter Regulator
House Air

HEPA Filter HEPA Filter

MFM Pump HEPA Filtered Purge

P MFM MFM
Carbon Filter Regulator
House Air

HEPA Filter HEPA Filter

MFM Pump HEPA Filtered Purge

P MFM

Figure 56. Schematic of Rea erosolization Test System

5.3.2 Test Procedure

The filtering facepeice was sealed to th e holder and placed in the exposure chamber described in Section 4.3.1 for loading. The breathing machine was started and pulled 85 L/min (2.3-L tidal volume, 37 breaths/min) through the filtering facepeice. The aerosol generation system was started to begin loading the filtering f acepiece. For both inert and biological aerosol, samples were also collected on 47-mm reference filters. The required loading duration was Filtering Facepiece

Collection Filter77 estimated based on the challenge concentration, flow rate, and filter surface area. It was assumed that the filtering facepieces were 100 percent efficient against all challenge aerosols. At the desired loading level, the aeros ol generation system and breathing machine were stopped and the
chamber flushed with HEPA filtered air. The filtering facepeice and holder were removed from the exposure chamber and sealed
to the reaerosolization chamber shown in Figure 56. The sample pump was started to flush the chamber with HEPA filtered air and sampling bega n with a pre-cough collect ion filter. Sample duration was sufficient to exchange the air with in the chamber three times (typically 15 to 25 minutes depending on sample flow rate). Th e sample pump was then stopped and the 47-mm collection filter replaced. The sample pump wa s started again and the breathing machine was used to simulate the cough. The cough profile wa s repeated three times. A valve was used such that the inhaled air between coughs was HEPA filtered room air. The chamber was again sampled for sufficient time to exchange the ch amber volume three times. The sample pump was stopped and the filter removed fr om the system for analysis. Polonium-210 static eliminators were used to minimize particle loss duri ng transport to laboratory for analysis.

5.3.3 Analytical Methods

Filtering facepiece loadings (#/cm 2 ) were estimated based on the loading of a 47-mm reference filter loaded simultaneously. The load ing on the reference filter was transformed to the loading on the filtering facepiece by taking into account the relative collection flow rates, durations, and surface areas (refer to Section 5.3. 5). The methods used to quantify the loading on the reference filters are described in Sections 5.3.2.1 and 5.3.2.2 for the inert and biological aerosols, respectively.

5.3.3.1 Inert Aerosols. The number concentrations of inert aerosols collected on the membrane filters were quantified using a fl uorescent microscope (Model SZX12, Olympus, Melville, NY) to count the particle s collected on selected regions of the filter. The area of the field-of-view was known based on the magnifica tion and allowed the number of particles/cm 2 to be determined. The method assumed that partic les were evenly distributed over the surface of the filter as only a percentage of the surface area was analyzed. The selected areas ranged from78 the center to the edge to identify any potential bi as in the radial directi on. As shown in Figure 57, five areas were analyzed for the loading filt ers and 20 areas were analyzed for the collection filters. More areas were analyzed for the colle ction filter due to the expected lower loading levels. Magnification for analysis of the loading filters was 45x resulting in a field of view that was 1 mm in diameter. Less magni fication (12x) was used for the co llection filter to increase the viewing area to 5 mm and maximi ze potential to locate particles. This permitted approximately 25 percent of the collection filter to be analyzed.

Figure 57. Analysis Patterns on 47-mm Coll ection Filters Used with Fluorescent Microscope to Quantify Loadings of Inert Particles

5.3.3.2. Biological Aerosols. The biological samples were collected on 47-mm filters for subsequent bioassay using the methods that were described in Section 4.3.3.1.

5.3.4 System Characterization

Shakedown tests were initially conducted to characterize th e test system and establish the proper operating conditions. Significant effort went into the design of the test chamber and several iterations were explored. The initial test chamber was cylindrical with an internal volume of only 10 L. The advantage of the rela tively small chamber was the short time required to flush the chamber when sampling at 40 L/mi n. However, the small chamber provided too much resistance for the breathing machine during the cough such that the 360 L/min peak flow could not be reached. Efforts to reduce pressure within the chamber were unsuccessful. It was79 not feasible to increase the sample flow rate en ough to adsorb the high peak flow. The highest flow rate that could be pulled through the membrane filter was 40 L/min. Using multiple collection filters or increasing the surface area would have been disadvantageous from the analytical perspective (i.e., low numbers of particles spread across a larger surface area). Thus, the chamber was scaled up to the final volume of 300 L/min. The cough profile was verified by measuring the flow rate using a rapid res ponse mass flow meter (Model 4000, TSI) that is capable of measuring and data logging the flow rate at 10 ms intervals. The measured cough profile is compared with the ta rget profile in Figure 58 and demonstrates the 360 L/min peak
flow was obtained.

0 50 100 150 200 250 300 350 400

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Time (Sec)FLow Rate (L/min) 0.8GERSON1740REP2 0.8GERSON1740REP3 0.8GERSON1740REP1 Target Cough Profile

Figure 58. Comparison of Target and Measured Cough Profile Used for Reaerosolization Testing

The larger chamber was disadvantageous from a sample collection pe rspective as longer sample durations were required and there was mo re surface area for particles to adhere. The chamber was designed to create an airflow pattern directed downward toward the collection filter to reduce particle loss to the chamber walls, dead s pots, or circulating air flow. In addition, the system was oriented such that gravity would enhance particle collection due to settling. A series of shakedown tests using the 0.8 μ m PSL challenge were performed to assess the sampling approach. Initially three 47-mm filters were co llected during each reaerosolization test: (1) a pre-cough filter to determine if particles were shed during the attachment of the loaded filter to the system, (2) a post-cough filter to collect particle s displaced by the cough, and (3) a post-test filter80 to verify the chamber was flushed. Particles were consistently collected on the pre-cough filter. The counts were not attributed to contamination within the test system as the post-test filters were generally found to have zero counts indicating minimal carryover between tests. Thus, the particles collected on the pre-cough filter were attributed to the physical process of connecting the loaded
filter to the chamber. Following the shakedown testing, only the pre- and post- cough samples were collected. The particle counts on the pre- and post-cough 47-mm filters are compared in Figure 59 for each of the trials completed with the 0.8 μ m PSL. The trials are shown in the order of completion. The postcough filters had higher counts in 15 of the 18 trials. The highest pre-cough counts were observed in trials 2 and 6 and both had higher counts than the post-cough filter from the previous test. Thus, the high counts were attributed to the process of connecting the filter to the test system. Unfortunately, no samples were collected between the pre- and post-cough filters to demonstrate the chamber had been completely flushed before the cough. Howeve r, even if the pre-cough filter is treated as a system background, the results demonstrate that particles were reaerosolized from the filtering facepieces as particle counts were generally higher post-cough. This trend was consistent throughout all challenge aerosols. The average particle counts pre- and post- cough are compared for each of the inert and biological challenges in Figure 60.

0 200 400 600 800 1000 1200

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Trial #Number of Particles Collected (#) Pre-Cough Post-Cough

Figure 59. Comparison of Number of Particles Collected on Pre- and Post-Cough Filters for Tests Performed with the 0.8 μ m PSL81 0.1

1 10 100 1000 10000 100000

MS2 "Wet" MS2 "Dry" Bg "Wet" 0.8 um PSL 2.2 um PSLAverage Number Particles Collected (#) Pre-Cough Post-Cough

Figure 60. Comparison of Number of Particles Collected on Pre- and Post-Cough Filters for Tests Performed with the Biological and Inert Aerosols

5.3.5 Calculation of Reaerosolization

The challenge aerosol concentration (C Chal ) was derived from the results of the reference filter analysis usi ng the following relationship:

L R R R Chal t Q A P L C × ×

= ) / (#

where P R is the loading density determin ed for the reference filter (#/cm 2 ), A R is the area of the reference filter (cm 2 ), Q R is the flow rate through the reference filter (L/min), and t L is the loading duration (min). The number of particles loaded (P FF ) onto the filtering facepiece was then determined using the following equation:82 L FF Chal FF t Q C P × × = ) (#

where Q FF is the flow rate through the filtering facepiece (L/min). It was assumed that the filters were 100 percent efficient fo r all challenge aerosols. The number of partic les reaerosolized (P C ) was based on the bioassay or fluorescence analysis of the collection filter. The percent of particles reaerosolized (f R ) was then the ratio of the number of particles reaerosolized (P C ) to the number of particles loaded on the filtering facepiece (P FF ):

100 (%) x P P f

FF C R =

5.4 Results

Table 19 summarizes the results of the reaero solization testing with both the inert and biological aerosols. Results from individual tria ls are summarized in Appendix J. The target loading level was 1 x 10 4 particles/cm 2 for all challenge aerosols with the exception of the higher loading tests performed with the 0.8 μ m PSL. The average measured loadings for each challenge type are also summarized in Table 19. Note that tests with the 2.2 μ m PSL and Bg "wet" aerosols had loading levels appr oximately an order-of-magnitude less than the target due to lower than expected challenge c oncentrations. In all cases, the percent reaerosolization was less than one percent of the number of particles loaded onto the filte ring facepiece. The inert aerosol
results are further discussed in Section 5.4.1 and the biological results in Section 5.4.2.83 Table 19. Summary of Reaerosolization Results

(a) No tests performed at test condition

5.4.1 Inert Aerosols

Figure 61 compares the percent reaerosoliza tion of inert particles measured from the MSA and Gerson respirators. All reaersolizations were less than 0.1 percent. The percent
reaerosolization tended to increase with increased particle size and was not significantly different
between the two brands of filte ring facepieces. Higher percent reaerosolizations were measured for the respirators that containe d exhalation valves. The increase was more significant for the smaller particles that were not reaersolized as easily from the filter media. Reaerosolization increased by a factor of 2 for the 2.2 μ m PSL and a factor of 4 to 8 for the 0.8 μ m PSL. The extent of reaerosolization was expected to be lower from the filters with exhalation valves as velocity through the aerosol media was likely lo wer due to the flow through the valve. However,
the mechanical movement of the valve and locali zed high velocity flow may have re-entrained particles collected on the surface of the valve or valve housing. To further investigate the higher reaerosolization, Gerson filtering facepieces with the exhalation valve covered with tape were
loaded with 0.8 μ m PSL. This prevented loading on the va lve and housing. The tape was then removed prior to the reaerosolization test. Figur e 62 compares these results with those from the Filter Type Gerson 1730 (No Ex. Valve) Gerson 1740 (Ex. Valve) MSA Affinity Plus (No Ex. Valve) MSA Affinity Plus (Ex. Valve) Reaerosolization (%) Challenge

Aerosol Average Loading (#/cm 2 ) Average 95% CI Average 95% CI Average 95% CI Average 95% CI 0.8 μ m

PSL 2.2 x 10 4 0.002 0.0003 0.008 0.0005 0.0008 0.0003 0.007 0.0007 0.8 μ m

PSL 1.7 x 10 5

- (a)
- - - 0.0006 0.00005 - - 0.8 μ m

PSL 9.4 x 10 5
- - - - 0.0004 0.00001 - - 2.2 μ m

PSL 2.0x10 3 0.03 0.005 0.04 0.006 - - - - Bg "wet" 1.0 x10 3 0.06 0.01 0.07 0.1 0.03 0.003 0.05 0.02 Bg "dry" 1.4x10 4 0.1 0.2 - - - - - MS2 "wet" 3.1 x10 4 0.07 0.08 0.1 - 0.07 0.08 0.1 0.1 MS2 "dry" 4.5 x10 4 0.5 0.2 0.7 0.2 - - - -84 Gerson respirators with no or unprotected valves . The percent reaeroso lization decreased by a factor of 2 as compared to tests with the unprotected valves.

0.0001

0.001

0.01

0.1

MSA (w/o valve) MSA (w/valve) Gerson (w/o valve) Gerson (w/valve)% Reaerosolized 0.8 um PSL 2.2 um PSL

Figure 61. Comparison of Percent Reaeroso lization of Inert Particles from MSA and Gerson Filtering Facepieces

0.0001

0.001

0.01

0.1

Gerson (w/o valve) Gerson (w/valve, protected) Gerson (w/valve)% Reaerosolized

Figure 62. Comparison of Percent Reaerosolization of 0.8 μ m PSL from Gerson Respirator with Exhalation Valve Protected during Loading85 The effect of loading on the percent reaeroso lization of 0.8 μ m PSL is shown in Figure 63. Although averages were less than 0.002 percen t for all loadings, the percent reaerosolization tended to decrease as the loading increased. Howe ver, more particles were reaerosolized at the higher loading levels. The average numbers of pa rticles reaerosolized for the different loading levels were 35, 180, and 740 particles. Thus, as loading increased by an order-of-magnitude, the average number of particles reaerosolized incr eased only by a factor of approximately 5.

0.0001

0.001

0.01

0.1

Normal (1E4/cm2) High (1E5/cm2) Ultra (1E6/cm2)% Reaerosolized

Figure 63. Comparison of Percent Reaerosolization of 0.8 μ m PSL from Gerson Respirator at Loadings Ranging from 1 x 10 4 to 1 x 10 6 Particles/cm 2

5.4.2 Biological Aerosols

This section summarizes the results of the reaerosolization testing completed with the biological aerosols. The results are also compared to the inert results described above. The Bg spore results are provided in S ection 5.4.2.1 and the MS2 phage results follow in Section 5.4.2.2.

5.4.2.1 Bg Spores. Figure 64 compares the measured reaersolization of the Bg "wet" and Bg "dry" aerosols to that measured for the inert 0.8 μ m PSL. Recall from Section 4.0, the AMMDs for both the "wet" and "dry " Bg were approximately 1.0 μ m. The mean86 reaerosolization of the Bg spores tended to be higher for the respirators with exhalation valves but the effect was not as signi ficant as observed with the 0.8 μ m PSL. The percent reaerosolization of the Bg spores was generally an order-of-magnitude higher than the inert PSL.

0.0001

0.001

0.01

0.1

1

MSA (w/o valve) MSA (w/valve) Gerson (w/o valve) Gerson (w/valve)% Reaerosolized 0.8 um PSL Bg wet Bg Dry

Figure 64. Comparison of Inert and Bg Spore Reaerosolization Results

5.4.2.2 MS2 Phage. Figure 65 compares the extent of reaerosolization of MS2 "wet" and "dry" aerosols with the 2.2 μ m PSL. The NMD of the MS2 "dry" aerosol was 2.3 μ m while
the "wet" was 0.2 μ m. Significant differences in reaero solization were observed between the inert and biological aerosols. Of particular in terest was the extent of reaerosolization of
MS2 "wet" aerosol as it was a pproximately an order-of-magnitude higher than that observed for
the 2.2 μ m PSL. This was contrary to the inert results shown previously that indicated percent
reaersolization increased with particle size. The highest r eaerosolization percentages were observed for the MS2 "dry" aerosol with a mean ofapproximately 0.5 percent, nearly two ordersof-magnitude higher than the 2.2 μ m PSL results. This difference wa s attributed to polydisperse
size distribution of the MS2. Although both had similar NMDs , the PSL was monodisperse while the MS2 was polydisperse with significant mass between 2 and 5 μ m containing viable particles. Higher percent reaerosolization is expected as the partic le size approaches 5 μ m as87 was demonstrated by Qian et al. (1997a) who s howed reaerosolization increased from 0.05 to 6 percent as the particle size increased from 1.5 to 5.0 μ m.

0.0001

0.001

0.01

0.1

1

MSA (w/o valve) MSA (w/valve) Gerson (w/o valve) Gerson (w/valve)% Reaerosolized 2.2 um PSL MS2 Wet MS2 Dry

Figure 65. Comparison of Inert and MS2 Phage Reaerosolization Results

5.5 Summary and Discussion

A test method was developed to quantify the extent of reaerosolization from a filtering facepiece loaded with either an inert or biological aerosol. Te sts were performed to assess the effect of particle size, particle type, and loadi ng level. Two brands of filtering facepieces were tested, the MSA Affinity Plus and Gerson 1730. Th e levels and trends of reaerosolization were similar for both brands. For the inert aerosols, reaerosolization was obser ved to increase with increased particle size over th e range tested (0.8 to 2.2 μ m). This trend was consistent with that observed by Qian et al. (1997a) who at tributed this to increased drag force on the larger particles.
The extent of reaerosolization of 0.8 μ m particles from filtering facepieces without exhalation valves was very low (less than 0.002 percent or 1 in every 50,000 particles loaded). The percent reaerosolization increased by an order of magnitude when filter ing facepieces with exhalation
valves were tested. This was attributed to the movement of the valve and localized high velocity air that could re-entrain part icles collected on the surface of the valve or valve housing.88 Specifically for the 0.8 μ m PSL, the number of particles reaerosolized was observed to increase with increased loading over the range from 1 x 10 4 to 1 x 10 6 particles/cm 2 . However, the number of particles did not in crease proportionally to the incr eased loading. Increasing the loading by a factor of 10 only increased the number of particles reaerosolize d by a factor of 5. Further work is recommended to determine if similar trends hold for larger particles. The extent of reaerosolization of the biologi cal aerosols was greater than that observed
for the inert aerosols with a similar diameter . For example, reaerosolization of the 0.8 μ m PSL was very low (~0.002%) while r eaerosolization of the Bg spores was typically 0.05 to 0.1 percent. Similarly, r eaerosolization of the 2.2 μ m PSL was only 0.01 percent while reaerosolization of the MS2 "dry" aerosol was 0. 5 percent. The higher reaerosolization for the biological aerosols was attributed to their broader size distribution. For example, the MS2 "dry" aerosol had significant mass between 2.5 and 5.0 μ m that contained viable particles. As described above, the extent of reaerosolizati on has been shown to increase with increased particle size. Thus, it is importa nt to consider the entire size di stribution and not just the nominal particle size when selecting an inert simu lant for characterizing reaerosolization.

6.0 CONCLUSIONS AND RECOMMENDATIONS

The performance of NIOSH-approved N95 and P100 filtering facepieces has been assessed against both inert and bi ological aerosols under high flow conditions representative of ventilation rates during heavy activit y. For the inert particles, th e most penetrating particle size (MPPS) was generally between 0.1 and 0.2 μ m for the P100 cartridges and 0.05 and 0.10 μ m for the filtering facepieces and N95 cartridges. The penetrati on of submicron pa rticles tended to increase with flow rate and penetrations in excess of the NIOSH N95 and P100 requirements were measured. However, the intended use, type and size distribution of the particulate hazard, APF, and other factors must be considered to determine if this increase in penetration is significant with regard to the overall protective capabi lity of the respirator. As was discussed in Section 2.0, the prim ary factors that influence penetration are filtration velocity, particle size, and the properties of the filter media. This task strictly focused on the effect of filtration velocity and particle size. The properties of the media from the various filters were not compared to identify those that could account for differences in performance. It89 is recommended to characterize the media prope rties including fiber diameter, solidity, and
thickness. These values could then be used to model the penetrations using the single fiber theory developed by Lee and Liu (1980) and compar ed to the measured values contained in this report. Electret media are commonly used in N95 filters and filteri ng facepieces to lower
inhalation resistance. Electret me dia may be more susceptible to the high flow conditions as the collection mechanism is less efficient. Thus, fu rther testing to compare performance of electret
and mechanical media is recommended. In comparing penetrations measured under constant and cyclic flow conditions, the MIF and PIF were determined to be important pa rameters. For the P100 cartridges, similar penetrations were measured under co nstant and cyclic flow if the c onstant flow was equivalent to the MIF. However, it may be more important to consider the PIF when testing filtering facepieces or N95 cartridges, especially at the hi gh volumetric flow rates that can be experienced during heavy work loads. These filters are not well-suited for the high volumetric flow rate applications due to their lower surface areas as compared to th e P100 cartridges. Selecting a constant flow equivalent to the peak inhalati on flow generally provides a conservative estimate of filter performance under cyclic flow conditions. All cyclic flow testing performed in this task used a sinusoidal flow profile. Additional tes ting is recommended with alternative waveforms such as a trapezoidal that may be more realis tic during periods of heavy exertion (Kaufman and Hastings, 2005). A method was developed to predict cyclic flow penetrations based on measured penetrations over a range of constant flows. Th e method was applied to th e inert data generated in this task. Good agreement was observed betw een the predicted cyclic flow penetrations and those measured in this study. Similar to the recommendation above, me asured cyclic flow penetrations under different types of waveforms are needed to fu rther validate the predictive
method. The performance of NIOSH-approved N95 and P100 respirator filters has been assessed against bioaerosol challenges under high volumetri c flow conditions. Mean penetrations were below the penetration requirements for the respective filter types (i.e., penetration less than 5 percent for N95 and less than 0.03 percent for P100 filters) under all flow conditions tested. Penetrations of Bg spore aerosols through the P100 filters were typically below detectable limits and, thus, had penetrations at least an order-of-magnitude belo w the P100 requirement. The N9590 filters also were very efficient at removing the bacterial aerosol challenges as average penetrations were less than 0.5 percent. There were not significant differences in the penetrations measured using the Bg spore aero sols generated from liquid suspension and dry powder. The most penetrating of the biological aerosols tested was the "wet" MS2 phage as the particle size was closest to the MPPS. Pene trations through the N95 and P100 filters were typically less than 2 and 0.03 percent, respectively, under all flow conditions. An inert aerosol of similar aerodynamic di ameter was shown to provide a good estimate of performance against biological ae rosols (i.e., measured penetratio ns within a factor of five). The Bg spore "wet" and "dry" penetra tions agreed favorably with the 1.3 μ m PSL results. In magnitude, the MS2 "wet" pene trations through the cartridge s were typically between penetrations measured using the 0.3 and 0.7 μ m PSL challenges. Comp arisons were not made with the MS2 "dry" as penetrations were typically below detectable limits. This was consistent with the penetrations measured using a similar si zed inert aerosol (i.e., 2.9 μm PSL). The results demonstrated that testing with inert particles in the MPPS range provides a conservative estimate against the biological aerosols assessed in the stu dy. Finally, the results demonstrated that higher penetrations tended to be measured using an opti cal light scattering instrument such as the LAS to measure bacterial aerosol pene tration as compared to the bioa ssay approach. Thus, it provides a worst case penetration measurement. This is si gnificant due to the labor intensive nature of the bioassay method. A test method was developed to quantify the extent of reaerosolization from a filtering facepiece loaded with either an inert or biological aerosol. Al l tests were performed with a cough profile that had a peak flow of 360 L/min. Further work is recommended to assess the effect of cough profile and increa sed peak flow. Tests were perf ormed to assess the effect of particle size, particle type, and loading level. For the inert aerosols, reaerosolization was observed to increase with increased partic le size over the range tested (0.8 to 2.2 μ m). The
extent of reaerosolization of 0.8 μ m PSL particles from filtering facepieces without exhalation valves was very low (less than 0.002 percent or 1 in every 50,000 particle s loaded). For the
0.8 μ m PSL particles, percent reaerosolization from filters with an exhalation value increased by an order-of-magnitude. The number of partic les reaersolized was shown to increase with increased loading for the 0.8 μ m PSL particles. Further work is recommended to assess the91 effect of loading on reaerosolizat ion of particles larger than 1 μ m since they are easier to
reaerosolize. The extent of reaerosolization of the biologi cal aerosols was greater than that observed
for the inert aerosols with a similar AMMD. For example, reaerosolization of the 0.8 μ m PSL was very low (~0.002%) while r eaerosolization of the Bg spores was typically 0.05 to 0.1 percent. Similarly, r eaerosolization of the 2.2 μ m PSL was only 0.01 percent while reaerosolization of the MS2 "dry" was 0.5 percent. The higher reaerosolization for the biological
aerosols was attributed to their broader size dist ribution. For example, the MS2 "dry" aerosol had significant mass between 2.5 and 5.0 μ m that contained viable particles. As described above, the extent of reaerosolization increases with increased particle size. Thus, it is important to consider the entire size distribution and not just the nominal particle size when selecting an inert simulant for reaerosolization experiments.92 Blank93 LITERATURE CITED

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Caretti, D.M., Gardner, P.D., and Coyne, K.M., "Workplace Breathing Rates: Defining Anticipated Values and Ranges for Respirator Certification Testing" , U.S. Army Edgewood Chemical Biological Center Techni cal Report, ECBC – TR-316 (2004).
Chen, C.C., Lehtimaki, M., and Willeke, K., "A erosol Penetration through Filtering Facepieces and Respirator Cartridges" Am. Ind. Hyg. Assoc. J. 53 (9): pp 566-574 (1992).
Chen, S.K., Vesley, D., Brosseau, L.M., and Vin cent, J.H., "Evaluation of Single-Use Masks and Respirators for Protection of Health Care Workers Against Mycobacterial Aerosols." Am. J. Infection Control 22 (2): pp 65-74 (April 1994).
Code of Federal Regulations. Respiratory protecti on. Title 30, CFR, Part 11. Washington, DC: U.S. Government Printing Office, Offi ce of the Federal Register (1972).
Code of Federal Regulations. Respiratory protecti on. Title 42, CFR, Part 84. Washington, DC: U.S. Government Printing Office, Offi ce of the Federal Register (1995).

42 CFR Part 84. Respiratory Protection; Final Rule. Federal Register, Washington, D.C. Vol. 60, No. 110 (1995).
Department of Health and Human Services (DHHS) Publication 2003- 136, "Guidance for Filtration and Air-Cleaning Systems to Protect Building Environments from Airborne Chemical, Biological, and Radiological Attacks," (April 2003).94 Fardi, B., and Liu, B.Y.H., "Perfo rmance of Disposable Respirators." Part. Part. Syst. Charact. 8 : pp 308-314 (1991).
Hanley, J.T., and Foarde, K.K., "Validation of Respirator Filter Efficacy." Report by RTI International, Research Triangle Park, N. C., RTI Contract No. DAAD 19-02-C-0097, Project No. 08621 (March 30, 2003).
Harstad, B.J. and Filler, M.E., “Evaluatin of Air Filters with Submicron Viral Aerosols and Bacterial Aerosols,” Am. Ind. Hyg. A ssoc. J. pp. 280-290, May-June (1969).
Hinds, W.C., Aerosol Technology; Properties, Behavior, and Measurement of Airborne Particles. John Wiley & Sons, New York, New York: 1999.
Hofacre, K., Schumacher, P., Hecker, R., Forney , T., "Filtration Efficiency Assessment of HEPA Filters Against a Bioaerosol Challenge." Battelle Memorial Institute Report to U.S. Army/ERDEC Armored Systems Modernizati on Team, Contract No. SP0900-94-D-0002, Task No. 39, Delivery Order 19 (May 15, 1996).
Hofacre, K.C. and Forney, T.L., “Test Method for Measuring Mask Protection Factors Using a Bioaerosol Challenge.” Batte lle Memorial Institute Final Report, February (1996)
Johnson, B., Martin, D.D., and Resnick, I.G., "Efficacy of Selected Respiratory Protective Equipment Challenged with Bacillus subtilis subps. niger " Applied and Environmental Microbiology , 60(6): pp 2184-2186 (1994).
Jankowska, E., Reponen, T., Willeke, K., Grins hpun, S., and Choi, K., "Collection of Fungal Spores on Air Filters and Spore Reentrainment from Filters into Air" J. Aerosol Science , 31(8): pp 968-978 (2000).
Kaufman, J.W. and Hastings, S.,"Respirator y Demand During Rigorous Physical Work in a Chemical Protective Ensemble," J. of Occup. and Env. Hyg., 2:pp 98-110 (2005)
Martin, S.B. and Moyer, E. S., “Electrostatic Re spirator Filter Media : Filter Efficiency and Most Penetrating Particle Size Effects,” Appl. Occup. Env. Hyg. 15(8) pp. 609-617 (2000).
McCollough, N.V., Brosseau, L.M., and Vesley, D ., "Collection of Three Bacterial Aerosols by Respirator and Surgical Mask Filters Unde r Varying Conditions of Flow and Relative Humidity." Ann. Occup. Hyg. 41(6): pp 677-690 (1997).
McCullough, N.V., Brosseau, L.M., Vesley, D ., and Vinent. J.H., “Improved Methods for Generation, Sampling, and Recovery of Biol ogical Aerosols in Filter Challenge Tests,” Am. Ind. Hyg. Assoc. J. 59: pp 234-241 (1998).
Qian, Y., Willeke, K., Grinshpun, S.A., and Donnelly, J., "Per formance of N95 Respirators: Reaerosolization of Bacteria and Solid Particles." Am. Ind. Hyg. Assoc. J. 58: pp 876-880 (1997a).95 Qian, Y., Willeke, K., Ulevici ous, V., and Grinshpun, S., "Partic le Reentrainment from Fibrous Filters." Aerosol Sci. and Tech. 27: pp 394-404 (1997b).
Qian, Y., Willeke, K., Grinshpun, S.A., Donnelly, J., and Coffey, C.C., "Performance of N95 Respirators: Filtration Efficiency for Ai rborne Microbial and Inert Particles." Am. Ind. Hyg. Assoc. J. 59 : pp 128-132 (1998).
Ruuskanen, J., Chen, C.-C., Carpenter, D.R., Sher man, A., and Willeke, K ., "Aerosol Penetration Characteristics for Disposable Respirator Facepieces." J. Aerosol Sci. 19 (7): pp 1445-1448 (1988).
Stafford, R.G., Ettinger, H.J., and Rowland, T. J., “Respirator Cartridge Filter Efficiency under Cyclic- and Steady-Flow Conditions.” Am. Ind. Hyg. Assoc. J. May: pp 182-192 (1973).
Stevens, G.A. and Moyer, E.S., "Worst Case' Ae rosol Testing Parameters: I. Sodium Chloride and Dioctyl Phthalate Aerosol Filter Efficiency as a Function of Particle Size and Flow Rate." Am. Ind. Hyg. Assoc. J. 50 (5): pp 257-264 (1989).
Stuempfle, A. K, and Fischer, B.W., “Biologi cal Aerosol Hazard Assessments of Emergency Responders in Specific Scenarios: Summary Repo rt”, OMI-762, prepared by OptiMetrics, Inc. under Contract No: DAAD13-02-F-0028 for US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD, 15 January 2004.
Tui man, I.L. and Steenweg, L., “The Influen ce of Particle Shape on the Penetration through Fibrous Filters,” J. Aerosol Science , 29: pp S1163-S1164 (1998).
Wake, D., Bowry, A.C., Crook, B., and Brown, R.C., "Performance of Respirator Filters and Surgical Masks Against Bacterial Aerosols." J. Aerosol Sci. 28 (7): pp 1311-1329 (1997).
Willeke, K., Qian, Y., Donnelly, J., Ginshpun, S., and Ulevicius, V., "Penetration of Airborne Microorganisms Through a Surgical Ma sk and a Dust/Mist Respirator." Am. Ind. Hyg. Assoc. J. 57 : pp 348-355 (1996).96 BlankA-1 APPENDIX A

PHOTOGRAPHS OF CARTRIDGES AND FILTERING FACEPIECESA-2 Figure A-1. SEA HE-T P100 Cartridge

Figure A-2. Survivair 1050 P100 CartridgeA-3 Figure A-3. North 7506 N95 Cartridge

Figure A-4. MSA Flexi-Filter N95 CartridgeA-4 Figure A-5. 3M 8293 P100 Filtering Facepiece

Figure A-6. Moldex 2360 P100 Filtering FacepieceA-5 Figure A-7. MSA Affinity Plus N95 Filtering Facepiece

Figure A-8. Gerson 1730 N95 Filtering FacepieceA-6 BlankB-1 APPENDIX B

RATIONALE FOR SELECTING FLOW CONDITIONSB-2 B.1 Introduction

The cyclic flow conditions were selected based on an analysis of data completed by the U.S. Army's Edgewood Chemical Biological Cent er (ECBC) to assess the relationship between workload and ventilation rate (C aretti et al., 2004). A brief review of litera ture regarding unencumbered ventilation is provide d in Section B.2. For a comple te review, refer to Caretti et al. (2004). Section B.3 presents the data comp iled by ECBC illustrating the effect of breathing
resistance from an APR on ventilat ion at different work intensities. The rationale for the selected flow conditions is provided in Section B.4.

B.2 Unencumbered Ventilation

Incremental exercise testing permits a rapi d, yet thorough assessment of an individual’s cardiorespiratory responses to exercise, including the level of the subject’s exercise limitation. Typically, such testing spans a tolerable work ra te range from low to high levels, during which, large amounts of respiratory a nd cardiovascular data are coll ected up to and including the voluntary endpoint of testing. Many published reports have documented breathing patterns adopted by healthy humans during in cremental exercise [Blackie et al. (1991); Gallagher et al. (1987); Neder et al. (2001); Wasserman et al. (1987)]. In general, it has been demonstrated in subjects with various fitness le vels that increasing minute volumes are due to increases in both tidal volume and breathing frequency at low exercise intensities. At high exercise intensities, increases in minute volume are accomplished main ly by increasing breathing frequency, with tidal volume showing a plateau [Gallagher et al. (1987)]. Normal values and ranges of ventilation at maximal exercise with respect to age, sex, and body anthropometrics have also been establ ished using incremental testing. Blackie et al. (1991) exposed 231 subjects (120 women; 111 men) to a symptom-limited maximal progressive incremental cycle ergometer exer cise test. All subjects underwent a medical screening and physical examination, including spirometry for those who had a history of smoking. Competitive athletes were excluded. The test subject population was dispersed in equal numbers (n =20) in ten-year age categor ies of 20-29 years, 30-39 years, 40-49 years, 50-59 years, 60-69 years, and 70-79 years for each sex, with the exception of men over 70 yearsB-3 of age (n = 11). Measurements of minute volume ( E V

& ), tidal volume (V T ), and breathing frequency ( 

### f ) were obtained at the end of each subject’s exercise test when maximal performance had been attained. The mean values at maximal exercise ( E V

& max , V T max , and 

### f max ) are presented in Table B-1 for each age group for both sexes. Average E V

& max was 97 ± 25
L·min -1 for all male subjects and ranged from 66 ± 12 to 114 ± 23 L·min -1 . For females, average

E V

& max was 69 ± 22 L·min -1 and ranged from 48 ± 12 to 87 ± 17 L·min -1 . Independent of age,

E V

& max , and V T max were significantly greater (p<0.001) for males compared to females. There
was no difference in 

### f max between men and women.

Table B-1. Mean Values for Ventilatio n at the End of Maximum Exercise (Blackie et al ., 1991) Group and Age (yr) V E, max (L/min) F max (breaths/min) V T, max (L) Men 20-29 114 ± 23 42 ± 8 2.7 ± 0.4 Men 30-39 105 ± 30 40 ± 15 2.7 ± 0.6 Men 40-49 102 ± 23 36 ± 7 2.9 ± 0.6 Men 50-59 97 ± 15 36 ± 6 2.8 ± 0.3 Men 60-69 83 ± 14 33 ± 6 2.6 ± 0.4 Men 70-79 66 ± 12 30 ± 6 2.3 ± 0.4 Men Mean 97 ± 25 36 ± 9 2.7 ± 0.5 Women 20-29 87 ± 17 41 ± 7 2.2 ± 0.5 Women 30-39 88 ± 19 44 ± 8 2.0 ± 0.3 Women 40-49 74 ± 19 35 ± 8 2.1 ± 0.4 Women 50-59 60 ± 15 32 ± 8 1.9 ± 0.4 Women 60-69 56 ± 14 33 ± 9 1.7 ± 0.2 Women 70-79 48 ± 12 31 ± 7 1.6 ± 0.3 Women Mean 69 ± 22 36 ± 9 1.9 ± 0.4

Sue and Hansen (1984) reported values similar to Blackie et. al. (1991) for V T (2.28 ± 0.43 L) and 

### f (41.6 ± 9.6 min -1 ) at maximum exercise in a population of middle-aged men (mean age = 54 years, range 34 to 74 years). Comparable values of E V

& have also been reported for specific age and gender groups and individual subjects at maximum efforts of incremental cycling exercise. Wasserman et al. (1987) measured E V

& max values of 107 L·min -1 for a 55-year-old male executive, 89 L·min -1 for a 59 year old retired male shipyard worker,
70 L·min -1 for a 45-year-old female homemaker, and 90 L·min -1 for a 37 year old male shipyard machinist, all values that fall within age-specific data reported by Blackie et al. (1991).B-4 In a study of similar design to that of Blackie et al. (1991), Neder et al. (2001) assessed breathing patterns during incremental exercise of 120 normal, healthy, sedentary individuals (60 males, 60 females) evenly distributed in age groups of 20-39 years, 40-59 years, and 60-80 years. Although these investigators were primarily interested in developing normative ventilatory data at selected submax imal ventilatory stresses, maximal E V

& data were reported for each age group by sex. For females, Neder et al. (2001) recorded average E V

& max values of approximately 76 ± 14 L·min -1 , 67 ± 11 L·min -1 , and 50 ± 10 L·min -1 for the age groups of 20-39 years, 40-59 years, and 60-80 years. Maximal E V

& averaged 120 ± 28 L·min -1

, 99 ± 22 L·min -1 , and 77 ± 12 L·min -1 for the three ascending male age groups. Again, these values reflect the data reported by Blackie et al. (1991) for a similar subject population. Therefore, the data presented in Table A-1 serve as a reasonable representation of normal maximal ventilatory responses to exhaustive incremental exercise for a wide range of ages in
both males and females.

B.3 Preliminary ECBC Data Compilation

The data in Table B-2 represent analysis of breath-by-breath ventil ation data from three studies [Caretti et al. (2 004); Coyne (2001); Johnson et al. (1999)], and provide a preliminary assessment of the impact of resistance breathing on ventilation at different work rates. The effect of breathing resistance and exer cise intensity on measured breat hing frequency and tidal volume are graphically illustrated in Figur es B-1 and B-2. The 0.7 cm H 2 O/L/s resistance condition represents a “no mask” condition. The three other resistance conditi ons correspond to those imposed while wearing various air- purifying respirators (APRs). For reference, the resistance of the M40 military mask is approximately 2.7 cm H 2 O/L/s at 85 L/min. Both the mean tidal volume and breathing frequency tended to increase with increased work ra te for each inhalation group. The breathing frequency tended to increase in higher proportions at th e lower resistances. For example, the frequency increased by 65% as th e exercise intensity increased from 30 to 85%
at a resistance of 0.7 cm H 2 O/L/s. In comparison, the mean frequency only increased by 50% at
an inhalation resistance of 5.73 cm H 2 O/L/s. There was not a significant difference in the tidal volumes measured for specific exercise intensi ties with inhalation resistances between 1.84 andB-5 5.73 cm H 2 O/L/s. In several cases in cluding the 85% exercise intens ity, the tidal volume tends
to decrease with increased inhalation resistance.

Table B-2. Preliminary Data Compiled by ECBC to Assess Impact of Breathing Resistance and Work Intensity on Ventilation

V E (L/min) V T (L) F R (min -1 ) PIF (L/min) Estimated

Work Intensity (% VO 2 max) Inhalation Resistance (cm H 2 O/L/s) x S.D. x S.D. x S.D. x S.D.

30 0.7 26.1 1.4 1.0 0. 2 31.5 18.0 128.3 20.0

1.84 22.8 5.8 1.1 0. 2 22.6 6.9 140.6 62.4
3.2 21.0 7.3 1.1 0. 2 19.1 4.9 128.4 26.5
5.73 19.5 5.9 0.9 0. 2 26.6 16.9 116.9 37.7

40 0.7 26.9 7.6 1.1 0. 2 29.7 10.4 159.3 24.4

1.84 30.1 7.1 1.4 0. 4 22.4 3.6 179.6 96.4
3.2 30.0 7.9 1.4 0. 3 22.9 4.7 170.4 43.8
5.73 26.9 8.2 1.2 0. 3 27.2 10.9 177.5 77.8

50 0.7 31.1 10.5 1.1 0. 4 41.1 22.3 182.2 33.8

1.84 43.4 16.5 1.7 0. 5 26.7 3.5 211.1 58.1
3.2 37.1 8.6 1.5 0. 4 31.1 15.1 189.3 38.8
5.73 36.6 8.7 1.4 0. 4 30.1 9.5 232.7 87.7

70 0.7 46.2 14.1 1.4 0. 5 52.4 28.2 264.6 52.3

1.84 53.4 13.1 1.9 0. 6 32.4 10.6 239.1 54.4
3.2 57.2 14.8 1.8 0. 4 35.0 9.9 295.5 144.9
5.73 51.4 15.7 1.7 0. 6 36.6 11.7 349.7 94.0

85 0.7 67.4 32.1 1.7 0. 5 52.0 23.8 354.8 135.8

1.84 73.9 21.4 2.2 0. 6 35.7 11.5 305.6 95.8
3.2 75.5 23.6 2.1 0. 7 38.6 9.0 349.6 117.9
5.73 60.5 19.0 1.8 0. 5 40.1 14.4 395.4 103.4B-6 0 10 20 30 40 50 60 70 80 90

0.7 1.84 3.2 5.73 Inhalation resistance (cmH 2 O/L/s)Fr (min-1) 30% 40% 50% 70% 85%

Figure B-1. Average ( ± SD) Breathing Frequency (Fr) at Ex ercise Intensities of about 30%, 40%, 50%, 70%, and 85% of Maximal Oxygen Consumption (V O2 max) for Four Inhalation Resistance Conditions

0 0.5

1 1.5

2 2.5

3

0.7 1.84 3.2 5.73 Inhalation resistance (cmH 2 O/L/s)VT(L) 30% 40% 50% 70% 85%

Figure B-2. Average ( ± SD) Tidal Volume (V T ) at Exercise Intensitie s of 30%, 40%, 50%, 70%, and 85% of Maximal Oxygen Consumption (V O2 max) for Four Inhalation Resistance ConditionsB-7 B.4 Rationale for Selected Flow Conditions

The cyclic flow conditions, summarized in Table B-3, were selected based on the analysis described previously. The 40 L/min minute volume represents a moderate breathing condition to allow comparison with the penetrati ons measured at higher flows. The 85 L/minute volume corresponded to a work intensity of approximately 85 percent VO 2 max, respectively, as shown in Figures B-1 and B-2. The minute volume of 114 L/min corresponded to the average tidal volume and frequency during exhaustive increm ental exercise of 20 to 29-year-old males as measured by Blackie et al. (1991). Adding one standard de viation to this minute volume provides the final flow conditi on. It is noted that the measurements made by Blackie et al. were unencumbered and, thus, provide a conservative estimate of br eathing during maximal exercise under conditions of respirator wear.

Table B-3. Summary of Selected Cyclic Flow Conditions
Rate (breaths/min) Tidal Volume (L) Minute Volume (L/min) PIF (a) (L/min) MIF (b) (L/min) 25 1.6 40 130 85 37 2.3 85 270 175 42 2.7 115 360 230 44 3.1 135 430 275 (a) Peak inspiratory flow rate a ssuming ideal sinusoidal waveform (b) Mean inspiratory flow rate assuming ideal sinusoidal waveform

B.5 Constant Flow Conditions

Three constant flows were selected for te sting: 85, 270, and 360 L/min. The 85 L/min represented the constant flow rate used in NIOSH certificati on of N95 and P100 particulate respirator filters. The 270 and 360 L/min repres ented the peak inspiratory flow rates of the cyclic flows with minute volumes of 85 and 115 L/ min, respectively. In addition, the 270 L/min was approximately the mean inspiratory flow of the 135 L/min cyclic flow condition.B-8 B.6 References

Blackie, S.P., M.S. Fairbarn, N.G. McElvaney, P.G. Wilcox, N.J. Morrison, and R.L. Pardy. "Normal Values and Ranges for Ventilation an d Breathing Pattern at Maximal Exercise." Chest 100: 136-142 (1991).
Caretti, D.M., P.D. Gardner, and K.M. Coyne, "Workplace Breat hing Rates: Defining Anticipated Values and Ranges for Respirator Certification Testing," U.S. Army Edgewood Chemical Biological Center Technical Report, ECBC-TR-316, September (2004).
Coyne, K. “ Modeling the Pulmonary Effects of Respir atory Protective Masks During Physical Activity .” University of Maryland College Park (2001).
Gallagher, C.G., E. Brown, and M. Younes. "B reathing Pattern During Maximal Exercise and During Submaximal Exerci se with Hypercapnia." J. Appl. Physiol. 63: 238-244 (1987).
Johnson, A.T., W.H. Scott, C.G. Lausted, M.B. Benjamin, K.M. Coyne, M.S. Sahota, and M.M. Johnson. "Effect of Respirator Inspiratory Resi stance Level on Constant Load Treadmill Work Performance." Am. Ind. Hyg. Assoc. J. 60: 474-479 (1999).
Neder, J.A., L.E. Nery, C. Peres, and B.J. Whip p. "Reference Values for Dynamic Responses to Incremental Cycle Ergometry in Males and Females Aged 20 to 80." Am. J. Respir. Crit. Care Med. 164: 1481-1486 (2001).
Sue, D.Y. and J.E. Hansen. "Normal Values in Adults During Exercise Testing." Clin. Chest Med. 5: 89-98 (1984).
Wasserman, K., J.E. Hansen, D.Y. Sue, and B.J. Whipp. “ Principals of Exercise Testing and Interpretation .” Philadelphia: L ea & Febiger, 1987.C-1 APPENDIX C

SHAKEDOWN TESTING OF MODEL 3160C-2 C.1 Model 3160 Shakedown Testing

Shakedown tests were conducted to characte rize the test system and establish proper operating conditions. This included assessing th e effect of non-isoki netic sampling, flow calibrations, and characterization of the chal lenge particle size distribution.

C.2 No Filter Testing

Due to the range of flow conditions, it wa s not practical to sample isokinetically. However, non-isokinetic sampling is not expected to have a large effect for the small particle sizes (0.02 to 0.3 μ m). To confirm this, tests were initially conducted without a test filter in the exposure chamber (i.e., Lucite ® box). A penetration of 100 pe rcent would indicate agreement between the measured upstream and downstream c oncentrations. Figures C-1 and C-2 compare the measured penetrations at the constant and cy clic flow conditions for the cartridge testing. Figure C-3 compares the no-filter penetrations m easured at the filtering facepiece cyclic flow
conditions. Data were not collect ed under the constant flow conditi ons. The data represents the means of three independent trials and the error bars represent one sta ndard deviation. The measured penetrations were typically in th e 90 to 110 percent range . From a practical perspective, the differences are not expected to have a significan t impact on measured penetrations.

10 100 1000

0.02 0.05 0.1 0.2 0.3 Particle Size (um)Penetration (%)
42.5 L/min 135 L/min 180 L/min

Figure C-1. Penetrations Measured Wi thout Test Filter at Constant Flow Conditions for Cartridge TestingC-3 10 100 1000

0.02 0.05 0.1 0.2 0.3 Particle Size (um)Penetration (%) 0.8 L, 25 bpm 1.2 L, 37 bpm 1.4 L, 42 bpm 1.6 L, 44 bpm

Figure C-2. Penetrations Measured Without Test Filter at Cyclic Flow Conditions for Cartridge Testing

10 100 1000

0.02 0.05 0.1 0.2 0.3 Particle Size (um)Penetration (%) 1.6 L, 25 bpm 2.3 L, 37 bpm 2.7 L, 42 bpm 3.1 L, 44 bpm

Figure C-3. Penetrations Measured Without Test Filter at Cyclic Flow Conditions for Filtering Facepiece Testing

C.3 Challenge Characterization

Shakedown tests were performed to characte rize the particle size distributions of the challenge aerosols. The partic le size distribution is important since the Model 3160 uses a CPC that does not classify particles into discrete size ranges. Thus, all particles are assumed to be the particle size of interest. Th e Model 3160 was used to sequentia lly generate challenge aerosols with target mean particle sizes of 0.02, 0.05, 0.1, 0.2, and 0.3 μ m. An electrostatic classifier andC-4 CPC were used to measure the particle size distributions. The measured size distributions generated by the Model 3160 at a constant flow rate of 85 L/min are shown in Figures C-4 and C-5 for the salt and oil aerosols, respectively. Re call that a salt aerosol was used for testing the N95 filters and a dioctyl phthalate (DOP) aerosol for testing the P 100 filters. Distinct peaks are observed for both aerosol types at target mean particle sizes of 0.05, 0.1, and 0.2 μ m. However, a significant portion of the 0.3 μ m challenge is below the target particle size. In addition, the particle concentration is approximately an orde r of magnitude lower than the other challenges.

1 10 100 1000

10 100 1000 Size (nm)Concentration (#/cc) 0.05 um 0.1 um 0.2 um 0.3 um

Figure C-4. Measured Particle Size Distributions of Salt Aerosol Used to Challenge N95 Filters

10 100 1000 10000 100000

10 100 1000 Size (nm)Concentration (#/cc) 0.05 um 0.1 um 0.2 um 0.3 um

Figure C-5. Measured Particle Size Distributions of DOP Aerosol Used to Challenge P100 Filters
Figures C-6 and C-7 compare the measured si ze distributions of the 0.2, 0.3, and 0.4 μ m aerosols at constant flow rates of 85 and 360 L/min, respectively. Note the similarity between
the distributions of the 0.3 and 0.4 μ m aerosols. Both distributions tend to shift toward smallerC-5 particles as the flow rate is increased from 85 to 360 L/min. This is potentially due to increased evaporation caused by the additional di lution air, and could account for the increase in penetration observed with incr easing particle size over 0.2 μ m for the P100 filtering facepiece as
discussed in Section 3.5.2.1 of the report. Figures C-8 and C-9 compare the up- and downstream
distributions measured for the 0.4 μ m aerosol at 85 and 360 L/min. Note that only a small fraction of the particles pene trating are greater than 0.3 μ m. This shift in particle size could account for the increase in penetration with incr eased particle size observed for the filtering facepieces.

1 10 100 1000 10000 100000

19.5 23 . 3 2 7 .9 3 3 .4 40 4 7 .

8 57.3 68.5 8 2 98.2 1 1 8 1 4 1 168 2 0 2 2 41 289 3 4 6 4 1 4 496 594 7 1 0 851
Size (nm)Concentration (#/cc) 0.2 um 0.3 um 0.4 um

Figure C-6. Measured Size Distributions of the 0.2, 0.3, and 0.4 μ m DOP Challenges at Flow Rate of 85 L/minC-6 1 10 100 1000 10000 100000

1 9 .5 23.3 27.9 33.4 4 0 4 7 .8 57.3 68.5 82 98 . 2 1 18 141 168 202 2 4 1 2 8 9 346 414 496 594 7 1 0 8 51
Size (nm)Concentration (#/cc) 0.2 um 0.3 um 0.4 um

Figure C-7. Measured Size Distributions of the 0.2, 0.3, and 0.4 μ m DOP Challenges at Flow Rate of 360 L/min

0.1

1 10 100 1000 10000

1 9 . 5 2

2 .5 25.9 3 0 3

4 .6 40 46.1 5 3 . 3 6

1 .5 71 8 2 9

4 .7 109 1 2 6 146 168 195 2 2 5 259 300 3 4 6 4 0 0 461 533 6 1 5 710 820 9 4 7
Size (nm)Concentration (#/cc) 0.4 um Upstream 0.4 um Downstream

Figure C-8. Comparison of Measured Size Distributions Upstream and Downstream of Moldex P100 Filter at a Flow Rate of 85 L/minC-7 0.1

1 10 100 1000 1000019.522.525.93034.64046.153.361.5718294.7109126146168195225259300346400461533615710820947 Size (nm)Concentration (#/cc)

0.4 um Upstream 0.4 um Downstream

Figure C-9. Comparison of Measured Size Distributions Upstream and Downstream of Moldex P100 Filter at a Flow Rate of 360 L/minC-8 BlankD-1 APPENDIX D

SHAKEDOWN OF TEST SYSTEM FO R LARGE PARTICLE INERT TESTINGD-2 D.1 Large Particle Shakedown Testing

Shakedown tests were completed to veri fy the proper operating conditions of the system. This included both no-filter testing to identify any potential sampling bias between the up- and downstream samples, and characterizing the challenge aerosol.

D.2 No Filter Testing

Shakedown tests without a f iltering facepiece or cartridge in the system were completed to identify any potential sampli ng bias between the up- and downstream measurements. The PSL with nominal diameters of 0.7, 1.3 and 2.9 μ m were generated at th ree different constant
flow rates. The measured no-f ilter penetrations are provided in Figure D-1. The results are based on the average of three independent trials at each test condition. The error bars represent one standard deviation. A pe netration of 100 percent would re present agreement between the upstream and downstream measurements and no sampling bias. For the 0.7 and 1.3 μ m particles, the measured penetrations ranged between 90 and 110 percent. However, the measured penetration of the 2.9 μ m particle tended to decrease with increased flow rate indicating a sampling bias downstream for this particle size. Similar trends are observed under the cyclic flow conditions as shown in Figure D-2.

10.00 100.00 1000.00

42.5 180 360 Flow (L/min)% Penetration 0.67 um 1.3 um 2.9 um

Figure D-1. Penetrations Measu red Without Test Filter at Constant Flow ConditionsD-3 10.00 100.00 1000.00

20 67.5 135 Minute Volum (L)Penetration (%)
0.67 um 1.3 um 2.9 um

Figure D-2. Penetrations Measured Without Test Filter at Cyclic Flow Conditions

The no-filter penetrations with the 2.9 μ m PSL are also shown in Figure D-3 as a function of flow rate. Each data point represents the mean of at least two trials and the error bars represent one standard deviation. The data points are connected by lines to emphasize the trends. These results were used to generate correcti on factors that could be applied to the 2.9 μ m PSL results specific to each flow condition. However, the measured penetrations were below detectable limits in all cases (<0.001%), so it was not necessary to correct the data.

40.00 50.00 60.00 70.00 80.00 90.00 100.00 110.00

0 50 100 150 200 250 300 350 400 Flow (L/min)% Penetration Constant Flow Cyclic Flow

Figure D-3. 2.9 μ m PSL No Filter Penetration fo r Cyclic and Constant FlowsD-4 Further experiments were performed to ch aracterize the sampling technique for the
2.9 μ m aerosol. The downstream expansion chamber was removed and replaced with a tee fitting (with an approximate diameter of 2.5 cm ) that allowed the insertion of isokenetic sampling probes with various inlet diameters, as summarized in Table D-1. Each probe was used to sample downstream during no-filter testing at a constant flow ra te of 360 L/min. The results, shown in Figure D-4, indicated that the measur ed penetration tended to increase as the probe inlet diameter increased. Penetrations rangi ng from 90 to 95 percent were measured using probes 6 through 8.

Table D-1. Summary of Isokine tic Probe Inlet Dimensions Probe Number Inlet ID (in) Inlet ID (cm) 2 1/16 0.16 4 1/8 0.32 5 5/32 0.40 6 3/16 0.48 7 7/32 0.56 8 1/4 0.64

10 100 1000

45678 Probe Diameter (#/32 in.)% Penetration

Figure D-4. Penetrations Measured Wi thout a Test Filter at 360 L/min With Probes of Various Inlet Diameters

Probe 6 and a 0.3 cm ID probe located near the inlet of the downst ream tubing, directly underneath the filter holder, were used to sample a 2.9 μ m challenge downstream at different
flow rates. The results are s hown in Figure D-5. The percen t penetration measured at eachD-5 sample location and flow rate represents a single trial. The measurements were all between 85 and 115 percent. From a practical perspective, the differences are no t expected to have a significant impact on measured penetrations.

10 100 1000

42.5 180 360 Flow (L/min)% Penetration

Downstream Inlet Probe Probe # 6 Inline

Figure D-5. Comparison of Measured Penetrations Made Using Two Different Sampling Probes

D.3 Challenge Aerosol Characterization

Shakedown testing was also completed to assess the stability of the challenge concentration, which is require d to sequentially make aerosol measurements between up- and downstream. Figure D-6 illustrates the length of time required for the challenge to reach steady
state at various constant flow condi tions. The challenge aerosol was 1.3 μ m PSL generated using a 6-jet Collison nebulizer. As expected, the re quired duration to reach steady state increased with decreased flow rate. The challenge concen tration reached steady-state within 5 minutes at
the 180 and 360 L/min flow conditions. It took approximately 10 minutes at 135 L/min and
20 minutes at 42.5 L/min. These times are consiste nt with those expected based on the flow rate and test chamber volume. Recall, the test filte r is bypassed during startup to prevent loading of
the filter. Note that the aerosol concentration decreased as the flow rate increased, due to the
additional dilution air.D-6 0 200 400 600 800 1000 1200 1400

0.0 5.0 10.0 15.0 20.0 25.0 30.0 Time (min)Challenge Concentration (#/cc) 42.5 L/min 135 L/min 180 L/min 360 L/min

Figure D-6. Challenge Aerosol Concentration During System Startup

The same test was also performed with the 2.9 μ m PSL at a flow rate of 135 L/min. The measured challenge concentration as a func tion of time is shown in Figure D-7. It took approximately 5 minutes for the chamber to reach steady state. Figure D-7 also compares concentration measurements made using the AP S with and without th e diluter (Model 3302A, TSI). Measurements made without the dilute r were more consistent and, thus, the 2.9 μ m challenge tests were not diluted pr ior to measurement. Note that the challenge concentration was only 20 particles/cc. The challenge concentr ation was increased by using a 24-jet Collison nebulizer and removing the charge neutralizer (Model 3012, TSI) from the test system. Figure D-8 shows the challenge concentration as a functi on of time at a flow rate of 135 L/min after the
modifications. The concentration reache d approximately 160 pa rticles/cc after
5 minutes.D-7 0 5 10 15 20 25 30

0 2 4 6 8 10 12 14 16 Time (min)Challenge Concentration (#/cc) No Diluter Diluter

Figure D-7. Comparison of 2.9 μ m Challenge Aerosol Concentration Measured Using the APS With and Without the Diluter

0 20 40 60 80 100 120 140 160 180

0 5 10 15 20 25 Time (min)Challenge Concentration (#/cc)

Figure D-8. Measured Challenge Concentration of 2.9 μ m PSL During System Startup at a Flow Rate of 135 L/min

Due to the large test matrix, conducting 0.67 and 1.3 μ m PSL tests simultaneously was considered advantageous. The mixture was aer osolized using the 6-jet Collison nebulizer. Figure D-9 illustrates the challenge concentration as a function of time fo r both particle sizes. The size distribution measured using the APS is shown in Figure D-10 and indicates two distinct peaks at the desired particle sizes. Aeroso l penetrations through the MSA Flexi-Filter ® were made using each particle size indivi dually and as a mixture. Similar penetrations were measuredD-8 with both approaches, as shown in Ta ble D-2. Thus, testing 0.67 and 1.3 μ m PSL simultaneously was performed to reduce the number of tests. The 2.9 μ m particles could not be
included in the mixture since the diluter was required to measure the 0.67 and 1.3 μ m challenge
concentrations.

0 500 1000 1500 2000 2500

0 5 10 15 20 25 Time (min)Challenge Concentration (#/cc) 0.67 um PSL 1.3 um PSL

Figure D-9. Challenge Concentration of 0.67 and 1.3 μ m PSL Generated from a Mixture Using Collison Nebulizer

0 100 200 300 400 500 600 700 800<0.5230.5830.6730.7770.8981.0371.1971.3821.5961.8432.1292.4582.8393.2783.7864.3715.048

Size ( μ m)Concentration (#/cc)

Figure D-10. Particle Size Distribu tion Measured Using APS of 0.67 and 1.3 μ m PSL Mixture Generated Using Collison NebulizerD-9 Table D-2. Comparison of Measured Penetrations through MSA Flexi-Filter Using 0.67 and 1.3 μ m PSL Aerosolized Individually and as Mixture

As mentioned previously, it would be beneficial to conduct 0.7, 1.3, and 2.9 μ m filter tests simultaneously. A 6-jet Co llison nebulizer was used to aerosolize Emery 3004 oil. The
size distribution based on number concentration as measured using the APS is shown in Figure D-11. Adequate concentrations of 0.7, 1.3, and 2.9 μ m particles were generated to measure oil efficiencies with all three particle sizes duri ng a single trial. Thus, the 0.7, 1.3, and 2.9 μ m oil tests were performed simultaneously.

0 200 400 600 800 1000 1200

0.542 0 .673 0.8 35 1.03 7 1.286 1.596 1.9 81 2.458 3.051 3.786 4. 698 5.8 29 7.234 8.977

Size (um)Concentration (#/cc)

Figure D-11. Distribution of Emery 3004 Aerosol Generated Using Collison Nebulizer

Shakedown testing was performed to verify the assumption that the supermicron test system was well mixed. An oil challenge was ge nerated with a 6-jet Collison Nebulizer. The aerosol exiting the nebulizer mixed with dry, filtered house air and pa ssed through a charge neutralizer (Model 3012, TSI) before entering the chamber. An exhaust flow of 180 L/min was Measured Penetration (%) Challenge 0.67 μ m 1.3 μ m 0.67 μ m PSL 0.358 - 0.67 μ m PSL 0.289 - 1.3 μ m PSL - 0.0263 1.3 μ m PSL - 0.0254 Mixed (0.67 and 1.3 μ m PSL) 0.378 0.0263 Mixed (0.67 and 1.3 μ m PSL) 0.351 0.0284D-10 drawn through a filter mounted in a filter hol der. A significant amount of 0.67 and 1.3 μ m oil particles was generated. Two tests were comple ted using two different probes. The first test used a long straight sample probe to sample from the left side of the chamber, center of the chamber, and right side of the chamber. The sec ond test used a curved probe to sample from the front of the chamber, the center of the chamber, and the back of the chamber. Both probes were inserted through the center of the chamber’s left side panel. The combined results of both tests showed a slight concentration incr ease from right to left and littl e difference from front to back for both particle sizes tested. A top view of the chamber, with a comparison of the 1.3 μ m concentrations, is shown in Figure D-12. The percentages shown were calculated by dividing the concentration found from each section by the co ncentration found in the center and multiplying by 100 percent.

106 %

113 % 100 % 86 %

107 %

Front

Figure D-12. Top View of Sup ermicron Test System with 1.3 μ m Concentrations Shown as a Percentage of the Center ConcentrationE-1 APPENDIX E

SUMMARY OF MEASURED INERT FILTRATION EFFICIENCIESE-2 Table E-1. Summary of Measured Penetrations through SEA HE-T Cartridge

Particle Size ( μ m) 0.02 0.05 0.1 0.2 0.3 0.7 1.3 2.9 Flow Rate (L/min) Trial Penetration (%) 1 <0.0001 <0.0001 0.0002 0.0004 0.0003 <0.0001 <0.0001 <0.0001 2 <0.0001 <0.0001 0.0003 0.0006 0.0003 <0.0001 <0.0001 <0.0001 3 <0.0001 <0.0001 0.0002 0.0003 0.0002 <0.0001 <0.0001 (a) x <0.0001 <0.0001 0.0002 0.0004 0.0003 <0.0001 <0.0001 <0.0001 42.5

σ - - 0.0000 0.0001 0.0001 - - -

1 0.0001 0.002 0.009 0.012 0.006 <0.0001 <0.0001 <0.0001 2 0.0001 0.002 0.008 0.011 0.005 <0.0001 <0.0001 <0.0001 3 0.0001 0.002 0.010 0.012 0.006 <0.0001 <0.0001 (a) 4 (b) (b) (b) (b) (b) <0.0001 <0.0001 (b) x 0.0001 0.002 0.0091 0.012 0.006 <0.0001 <0.0001 <0.0001 135

σ 0.0000 0.0004 0.0010 0.0009 0.0008 - - -

1 0.005 0.008 0.029 0.030 0.019 <0.0001 <0.0001 <0.0001 2 0.002 0.009 0.027 0.021 0.012 <0.0001 <0.0001 <0.0001 3 0.001 0.005 0.030 0.018 0.010 <0.0001 <0.0001 <0.0001 x 0.003 0.007 0.029 0.023 0.014 <0.0001 <0.0001 <0.0001 180

σ 0.002 0.002 0.001 0.006 0.005 - - -

1 <0.0001 <0.0001 0.0002 0.0003 0.0002 <0.0001 <0.0001 <0.0001 2 0.0001 <0.0001 0.0001 0.0003 0.0002 <0.0001 <0.0001 <0.0001 3 <0.0001 <0.0001 0.0002 0.0003 0.0002 <0.0001 <0.0001 (a) x 0.0001 <0.0001 0.0001 0.0003 0.0002 <0.0001 <0.0001 <0.0001 20 (c)

σ - - 0.0000 0.0000 0.0000 - - -

1 0.0002 0.001 0.006 0.009 0.003 0.0001 <0.0001 <0.0001 2 0.0001 0.0009 0.005 0.007 0.005 <0.0001 <0.0001 <0.0001 3 0.0001 0.0003 0.002 0.002 0.002 <0.0001 <0.0001 (a) x 0.0001 0.0008 0.004 0.006 0.003 0.0001 <0.0001 <0.0001 42.5 (c)

σ 0.0000 0.0004 0.002 0.003 0.002 - - -

1 0.0004 0.002 0.010 0.013 0.007 0.0012 <0.0001 <0.0001 2 0.0005 0.001 0.005 0.006 0.004 <0.0001 <0.0001 <0.0001 3 0.0006 0.001 0.005 0.006 0.006 <0.0001 <0.0001 (a) 4 (b) (b) (b) (b) (b) <0.0001 <0.0001 (b) x 0.0005 0.002 0.006 0.008 0.006 0.0004 <0.0001 <0.0001 57.5 (c)

σ 0.0001 0.0007 0.003 0.004 0.002 - - -

1 0.001 0.004 0.016 0.018 0.010 <0.0001 <0.0001 <0.0001 2 0.001 0.002 0.007 0.009 0.008 <0.0001 <0.0001 <0.0001 3 0.002 0.002 0.008 0.010 0.010 <0.0001 <0.0001 (a) x 0.001 0.003 0.010 0.012 0.010 <0.0001 <0.0001 <0.0001 67.5 (c)

σ 0.0003 0.001 0.005 0.005 0.001 - - - (a) Only two tests planned (b) Test not planned (c) Cyclic flow minute volumeE-3 Table E-2. Summary of Measured Penetr ations through Survivair 1050 Cartridge

Particle Size ( μ m) 0.02 0.05 0.1 0.2 0.3 0.7 1.3 2.9 Flow Rate (L/min) Trial Penetration (%) 1 0.0003 0.003 0.008 0.009 0.006 <0.0001 <0.0001 <0.0001 2 0.0001 0.002 0.006 0.008 0.004 <0.0001 <0.0001 <0.0001 3 0.0001 0.002 0.007 0.008 0.004 <0.0001 <0.0001 (a) x 0.0002 0.002 0.007 0.008 0.005 <0.0001 <0.0001 <0.0001 42.5

σ 0.0001 0.0005 0.0007 0.0010 0.001 - - -

1 0.003 0.037 0.093 0.059 0.035 <0.0001 <0.0001 <0.0001 2 0.004 0.043 0.10 0.064 0.038 <0.0001 <0.0001 <0.0001 3 0.005 0.048 0.10 0.063 0.039 <0.0001 <0.0001 (a) x 0.004 0.043 0.098 0.062 0.037 <0.0001 <0.0001 <0.0001 135

σ 0.001 0.005 0.005 0.003 0.002 - - -

1 0.025 0.12 0.23 0.12 0.086 0.0001 <0.0001 <0.0001 2 0.021 0.097 0.19 0.10 0.068 0.0001 <0.0001 <0.0001 3 0.008 0.029 0.046 0.030 0.034 <0.0001 <0.0001 (a) x 0.018 0.084 0.16 0.086 0.063 0.0001 <0.0001 <0.0001 180

σ 0.009 0.050 0.097 0.049 0.027 0.0000 - -

1 0.0002 0.002 0.016 0.010 0.008 0.0001 <0.0001 <0.0001 2 0.0002 0.002 0.008 0.010 0.006 <0.0001 <0.0001 <0.0001 3 0.0003 0.003 0.010 0.013 0.007 0.0011 <0.0001 (a) x 0.0002 0.003 0.011 0.011 0.007 0.0006 <0.0001 <0.0001 20 (b)

σ 0.0001 0.0005 0.004 0.002 0.0008 0.0008 - -

1 0.003 0.019 0.049 0.036 0.018 <0.0001 <0.0001 <0.0001 2 0.003 0.019 0.046 0.036 0.014 <0.0001 <0.0001 <0.0001 3 0.003 0.021 0.049 0.033 0.016 <0.0001 <0.0001 (a) x 0.003 0.020 0.048 0.035 0.016 <0.0001 <0.0001 <0.0001 42.5 (b)

σ 0.0003 0.001 0.001 0.002 0.002 - - -

1 0.005 0.029 0.066 0.041 0.020 <0.0001 <0.0001 <0.0001 2 0.004 0.030 0.076 0.051 0.022 <0.0001 <0.0001 <0.0001 3 0.010 0.044 0.097 0.072 0.035 <0.0001 <0.0001 <0.0001 x 0.006 0.034 0.080 0.055 0.026 <0.0001 <0.0001 <0.0001 57.5 (b)

σ 0.004 0.008 0.016 0.016 0.008 - - -

1 0.013 0.064 0.13 0.078 0.032 <0.0001 <0.0001 <0.0001 2 0.009 0.047 0.097 0.059 0.041 <0.0001 <0.0001 <0.0001 3 0.016 0.063 0.12 0.083 0.044 <0.0001 <0.0001 <0.0001 x 0.013 0.058 0.12 0.074 0.039 <0.0001 <0.0001 <0.0001 67.5 (b)

σ 0.003 0.010 0.018 0.013 0.007 - - - (a) Only two tests planned (b) Cyclic flow minute volumeE-4 Table E-3. Summary of Measured Pene trations through North 7506 Cartridge

Particle Size ( μ m) 0.02 0.05 0.1 0.2 0.3 0.7 1.3 2.9 Flow Rate (L/min) Trial Penetration (%) 1 4.9 8.5 3.2 1.9 1.0 0.0 0.00 0.0001 2 5.9 9.0 3.3 1.8 1.0 0.2 0.03 <0.0001 3 5.8 9.0 3.5 1.9 1.1 0.2 0.03 (a) x 5.5 8.8 3.4 1.9 1.0 0.2 0.02 0.0000 42.5

σ 0.6 0.3 0.2 0.1 0.0 0.1 0.01 0.0000

1 16.3 18.6 9.9 8.4 5.9 2.7 0.07 0.0002 2 14.6 17.9 9.7 8.8 5.9 2.4 0.08 <0.0001 3 9.8 14.7 9.1 5.9 3.8 2.8 0.09 (a) x 13.6 17.1 9.6 7.7 5.2 2.6 0.08 0.0001 135

σ 3.4 2.0 0.4 1.5 1.2 0.2 0.01 0.0001

1 17.6 21.5 14.2 13.8 9.9 3.7 0.07 0.0002 2 20.5 21.6 14.9 14.2 9.8 1.8 0.06 0.0004 3 16.8 19.5 11.9 14.2 9.8 2.9 0.05 (a) x 18.3 20.8 13.7 14.1 9.9 2.8 0.06 0.0003 180

σ 1.9 1.2 1.6 0.2 0.0 1.3 0.01 0.0002

1 6.8 6.1 2.9 2.2 1.5 0.4 0.04 <0.0001 2 6.6 6.4 2.7 2.2 1.9 0.7 0.07 <0.0001 3 7.4 8.6 2.9 2.2 1.2 0.6 0.06 (a) x 6.9 7.0 2.9 2.2 1.5 0.5 0.06 <0.0001 20 (b)

σ 0.5 1.3 0.1 0.0 0.4 0.1 0.02 -

1 11.3 13.0 6.0 5.4 3.7 2.0 0.09 <0.0001 2 12.4 14.3 7.9 7.0 5.0 1.7 0.08 <0.0001 3 8.1 9.2 4.3 3.0 1.7 0.5 0.01 (a) x 10.6 12.2 6.1 5.1 3.5 1.4 0.06 <0.0001 42.5 (b)

σ 2.2 2.6 1.8 2.0 1.6 0.8 0.05 -

1 15.5 18.3 9.4 8.2 5.8 3.5 0.13 <0.0001 2 15.3 17.0 9.5 8.7 7.4 2.6 0.09 0.0004 3 14.1 16.5 9.4 8.4 7.1 2.7 0.09 (a) x 15.0 17.3 9.4 8.5 6.8 2.9 0.10 0.0003 57.5 (b)

σ 0.7 0.9 0.1 0.3 0.8 0.5 0.03 -

1 18.4 21.7 12.3 11.0 7.9 0.9 0.01 0.0028 2 19.2 15.9 10.2 11.0 6.4 2.6 0.07 0.0005 3 18.8 18.8 10.9 11.0 8.3 2.6 0.07 (a) x 18.8 18.8 11.2 11.0 7.5 2.0 0.05 0.0016 67.5 (b)

σ 0.4 2.9 1.1 0.0 1.0 1.0 0.03 0.0016 (a) Only two tests planned (b) Cyclic flow minute volumeE-5 Table E-4. Summary of Measured Penetrations through MSA Flexi-Filter

Particle Size ( μ m) 0.02 0.05 0.1 0.2 0.3 0.7 1.3 2.9 Flow Rate (L/min) Trial Penetration (%) 1 0.2 0.4 0.1 0.0 0.0 0.00 0.00 <0.0001 2 0.2 0.8 0.3 0.1 0.0 0.01 0.00 <0.0001 3 0.2 0.8 0.4 0.1 0.1 0.00 0.00 (a) x 0.2 0.7 0.3 0.1 0.0 0.00 0.00 <0.0001 42.5

σ 0.0 0.2 0.1 0.1 0.0 0.00 0.00 -

1 2.2 5.3 2.7 1.8 1.0 0.25 0.03 <0.0001 2 2.1 3.1 1.7 1.0 0.5 0.29 0.02 <0.0001 3 2.0 5.2 2.8 1.9 1.2 0.40 0.02 (a) x 2.1 4.6 2.4 1.6 0.9 0.31 0.02 <0.0001 135

σ 0.1 1.2 0.6 0.5 0.4 0.08 0.00 -

1 2.6 2.8 2.1 1.7 1.1 0.65 0.04 <0.0001 2 3.7 5.7 4.2 3.4 2.9 0.90 0.03 <0.0001 3 4.6 9.4 6.9 5.2 3.3 0.53 0.03 (a) x 3.7 6.0 4.4 3.4 2.4 0.69 0.03 <0.0001 180

σ 2.6 2.8 2.1 1.7 1.1 0.26 0.00 -

1 0.5 0.9 0.5 0.3 0.2 0.01 0.00 <0.0001 2 0.8 1.2 0.6 0.6 0.6 0.02 0.00 <0.0001 3 0.7 1.0 0.6 0.6 0.8 0.01 0.00 (a) x 0.7 1.0 0.6 0.5 0.6 0.01 0.00 <0.0001 20 (c)

σ 0.1 0.2 0.1 0.2 0.3 0.01 0.00 -

1 2.0 2.0 1.1 0.8 0.7 0.14 0.01 <0.0001 2 3.3 3.8 2.0 1.4 1.3 0.09 0.01 <0.0001 3 2.9 4.2 2.5 2.4 2.9 0.15 0.01 (a) x 2.7 3.3 1.9 1.5 1.6 0.13 0.01 <0.0001 42.5 (c)

σ 0.7 1.2 0.7 0.8 1.2 0.03 0.00 -

1 5.5 7.9 5.8 5.1 4.5 0.27 0.02 <0.0001 2 2.0 4.2 2.1 1.4 0.8 0.26 0.02 <0.0001 3 7.8 10.5 8.2 8.0 7.4 0.22 0.02 (a) 4 3.6 7.2 3.9 2.7 1.9 (b) (b) (b) x 4.7 7.5 5.0 4.3 3.6 0.25 0.02 <0.0001 57.5 (c)

σ 2.5 2.6 2.6 2.9 3.0 0.03 0.00 -

1 4.3 8.0 4.8 3.8 3.1 0.52 0.05 <0.0001 2 4.6 7.0 4.8 5.0 5.9 0.29 0.02 <0.0001 3 4.4 9.2 6.4 5.0 3.8 0.48 0.03 (a) x 4.4 8.1 5.3 4.6 4.3 0.43 0.03 <0.0001 67.5 (c)

σ 3.2 2.4 2.7 2.9 2.9 0.12 0.01 - (a) Only two tests planned (b) Test not planned (c) Cyclic flow minute volumeE-6 Table E-5. Summary of Measured Penetrations through 3M 8293

Particle Size ( μ m) 0.02 0.05 0.1 0.2 0.3 0.7 1.3 2.9 Flow Rate (L/min) Trial Penetration (%) 1 0.006 0.009 0.004 0.004 0.004 <0.0001 <0.0001 <0.0001 2 0.007 0.008 0.002 0.001 0.0008 0.0011 0.0004 <0.0001 3 0.011 0.014 0.005 0.005 0.006 <0.0001 <0.0001 <0.0001 x 0.008 0.010 0.004 0.003 0.004 0.0004 0.0002 <0.0001 85

σ 0.003 0.003 0.002 0.002 0.002 - - -

1 0.17 0.20 0.041 0.019 0.045 0.002 0.0001 0.0002 2 0.23 0.21 0.039 0.012 0.035 0.004 0.001 <0.0001 3 0.26 0.26 0.049 0.012 0.033 0.001 0.0002 <0.0001 x 0.22 0.22 0.043 0.014 0.038 0.002 0.0005 0.0001 270

σ 0.047 0.035 0.005 0.004 0.007 0.001 0.0005 -

1 0.61 0.52 0.17 0.12 0.30 0.002 0.0001 0.0001 2 0.43 0.33 0.11 0.19 0.37 0.002 0.0002 0.0001 3 0.58 0.31 0.17 0.11 0.27 0.002 <0.0001 0.0001 x 0.54 0.39 0.15 0.14 0.31 0.002 0.0001 0.0001 360

σ 0.098 0.12 0.035 0.04 0.055 0.0002 0.0001 0.0000

1 0.014 0.030 0.004 0.0003 0.0003 0.002 0.001 0.0006 2 0.010 0.025 0.003 0.0004 0.0004 0.0004 0.0003 0.0003 3 0.021 0.028 0.006 0.003 0.003 0.001 0.0008 0.0001 x 0.015 0.028 0.005 0.001 0.001 0.001 0.0008 0.0003 40 (b)

σ 0.005 0.003 0.001 0.002 0.002 0.0006 0.0005 0.0003

1 0.21 0.30 0.051 0.006 0.007 0.0001 <0.0001 <0.0001 2 (a) (a) (a) (a) (a) 0.0008 0.0005 0.0001 3 (a) (a) (a) (a) (a) 0.0006 0.0003 0.0001 x 0.21 0.30 0.051 0.006 0.007 0.0008 0.0005 0.0001 85 (b)

σ - - - - - 0.0003 0.0001 0.0000

1 0.45 0.43 0.086 0.012 0.018 0.0003 <0.0001 <0.0001 2 0.41 0.44 0.081 0.013 0.021 0.0002 <0.0001 <0.0001 3 0.42 0.52 0.094 0.017 0.021 0.0005 0.0002 0.0001 x 0.42 0.47 0.087 0.014 0.020 0.0003 0.0002 0.0001 115 (b)

σ 0.022 0.045 0.007 0.003 0.002 0.0002 - -
1 (a) (a) (a) (a) (a) 0.004 0.001 0.0003 2 (a) (a) (a) (a) (a) 0.001 0.0004 <0.0001 3 (a) (a) (a) (a) (a) 0.003 0.001 0.0001 x - - - - - 0.002 0.0009 0.0002 135 (b)

σ - - - - - 0.001 0.0005 0.0001 (a) Test not planned (b) Cyclic flow minute volumeE-7 Table E-6. Summary of Measured Penetrations through Moldex 2360

Particle Size ( μ m) 0.02 0.05 0.1 0.2 0.3 0.7 1.3 2.9 Flow Rate (L/min) Trial Penetration (%) 1 0.014 0.061 0.035 0.004 0.002 0.0002 <0.0001 <0.0001 2 0.007 0.026 0.010 0.0006 0.0002 0.0001 <0.0001 <0.0001 3 0.012 0.058 0.022 0.006 0.002 <0.0001 <0.0001 <0.0001 x 0.011 0.048 0.022 0.003 0.001 0.0002 <0.0001 <0.0001 85

σ 0.004 0.019 0.012 0.003 0.001 0.0001 - -

1 1.5 1.3 0.67 0.52 0.72 0.037 0.0003 0.0002 2 0.36 0.61 0.33 0.42 0.58 0.063 0.0001 0.0005 3 0.36 0.91 0.54 0.37 0.20 0.025 0.0017 0.0001 4 (a) (a) (a) (a) (a) 0.022 (a) 0.0001 x 0.75 0.94 0.51 0.43 0.50 0.037 0.0007 0.0002 270

σ 0.67 0.35 0.17 0.075 0.27 0.016 0.0009 0.0002

1 0.33 0.64 1.1 0.17 0.29 0.056 0.019 0.001 2 0.38 0.70 0.34 0.15 0.24 0.047 0.0001 0.004 3 1.9 2.2 1.6 1.4 1.6 0.04 0.0002 0.0006 4 (a) (a) (a) (a) (a) (a) (a) 0.0004 x 0.86 1.2 1.0 0.57 0.71 0.0490 0.0064 0.0014 360

σ 1.1 1.0 0.89 0.89 0.96 0.0023 0.0001 0.0015

1 0.009 0.081 0.032 0.004 0.059 0.0008 0.0005 0.0001 2 0.026 0.11 0.053 0.018 0.014 0.0005 0.0003 <0.0001 3 0.014 0.10 0.047 0.015 0.004 0.0002 <0.0001 <0.0001 4 (a) (a) (a) (a) (a) (a) (a) 0.0002 x 0.016 0.096 0.044 0.013 0.026 0.0005 0.0004 0.0001 40 (b)

σ 0.009 0.013 0.011 0.007 0.029 0.0003 0.0001 0.0000

1 0.18 0.70 0.30 0.047 0.016 0.009 0.0009 <0.0001 2 0.16 0.69 0.32 0.055 0.020 0.003 <0.0001 <0.0001 3 0.14 0.79 0.37 0.059 0.029 0.003 0.0001 <0.0001 x 0.16 0.73 0.33 0.054 0.022 0.005 0.0005 <0.0001 85 (b)

σ 0.023 0.057 0.037 0.006 0.007 0.003 0.0006 -
1 (a) (a) (a) (a) (a) 0.020 0.006 0.001 2 (a) (a) (a) (a) (a) 0.028 0.005 0.0001 3 (a) (a) (a) (a) (a) 0.013 0.0003 <0.0001 4 (a) (a) (a) (a) (a) 0.031 (a) (a) x - - - - - 0.023 0.004 0.0007 115 (b)

σ - - - - - 0.008 0.003 0.0008
1 (a) (a) (a) (a) (a) 0.016 0.001 0.0007 2 (a) (a) (a) (a) (a) 0.026 <0.0001 0.0001 3 (a) (a) (a) (a) (a) 0.014 <0.0001 <0.0001 x - - - - - 0.019 0.001 0.0004 135 (b)

σ - - - - - 0.007 - 0.0005 (a) Test not planned (b) Cyclic flow minute volumeE-8 Table E-7. Summary of Measured Penetr ations through MSA Affinity Plus

Particle Size ( μ m) 0.02 0.05 0.1 0.2 0.3 0.7 1.3 2.9 Flow Rate (L/min) Trial Penetration (%) 1 1.0 2.7 1.9 1.3 0.9 0.86 0.20 0.0006 2 1.3 3.3 2.4 1.8 1.4 1.1 0.21 <0.0001 3 0.6 2.4 1.6 1.2 1.0 0.81 0.19 (a) x 1.0 2.8 2.0 1.4 1.1 0.92 0.20 0.0004 85

σ 0.4 0.5 0.4 0.3 0.3 0.16 0.01 -

1 1.8 5.1 3.8 3.4 2.5 5.9 0.18 0.0026 2 5.4 9.1 8.3 7.8 6.0 2.0 0.04 0.0017 3 2.2 5.5 4.2 3.5 2.5 3.7 0.17 (a) 4 4.2 9.7 8.5 7.7 5.5 (b) (b) (b) 5 4.8 8.8 7.2 5.7 4.0 (b) (b) (b)

x 3.7 7.6 6.4 5.6 4.1 3.8 0.13 0.0022 270

σ 1.6 2.2 2.2 2.2 1.6 2.0 0.08 0.0006

1 4.8 7.9 7.6 7.1 5.6 3.82 0.13 0.0013 2 3.4 6.1 6.4 6.2 5.0 3.39 0.08 0.0007 3 3.1 6.8 6.8 6.4 5.2 5.86 0.15 (a) 4 6.0 10.7 10.1 9.1 7.1 (b) (b) (b) 5 5.9 10.4 10.4 9.2 7.4 (b) (b) (b) 6 5.1 9.6 8.7 8.0 6.3 (b) (b) (b)

x 4.7 8.6 8.3 7.7 6.1 4.36 0.12 0.0010 360

σ 1.2 1.9 1.7 1.3 1.0 1.32 0.04 0.0004

1 1.3 3.1 2.0 1.6 1.1 1.04 0.16 0.0004 2 1.3 2.8 1.9 1.7 1.0 1.42 0.23 0.0004 3 1.7 3.4 2.6 2.3 1.8 2.07 0.28 (a) x 1.4 3.1 2.2 1.8 1.3 1.51 0.22 0.0004 40 (c)

σ 0.2 0.3 0.4 0.4 0.5 0.52 0.06 0.0000

1 3.3 7.8 5.1 4.2 3.0 1.02 0.13 0.0001 2 4.6 7.6 6.1 5.4 3.7 2.14 0.16 0.0014 3 4.7 10.7 9.1 8.2 5.9 2.47 0.19 (a) x 4.2 8.7 6.7 5.9 4.2 1.87 0.16 0.0008 85 (c)

σ 0.8 1.7 2.1 2.0 1.5 0.76 0.03 0.0009

1 7.2 14.1 13.1 12.5 8.6 1.45 0.02 0.0002 2 8.5 13.3 12.5 11.2 8.5 3.67 0.15 <0.0001 3 6.5 12.8 11.9 10.3 7.2 4.32 0.24 (a) x 7.4 13.4 12.5 11.3 8.1 3.14 0.14 0.0002 115 (c)

σ 1.0 0.7 0.6 1.1 0.7 1.51 0.11 - 1 (b) (b) (b) (b) (b) 3.28 0.09 0.0006 2 (b) (b) (b) (b) (b) 2.64 0.07 0.0004 3 (b) (b) (b) (b) (b) 2.52 0.05 (a) x - - - - - 2.81 0.07 0.0005 135 (c)

σ - - - - - 0.41 0.02 0.0001 (a) Only two tests planned (b) Test not planned (c) Cyclic flow minute volumeE-9 Table E-8. Summary of Measured Penetrations through Gerson 1730

Particle Size ( μ m) 0.02 0.05 0.1 0.2 0.3 0.7 1.3 2.9 Flow Rate (L/min) Trial Penetration (%) 1 2.2 4.2 3.0 2.5 1.7 0.47 0.12 0.0059 2 2.0 4.1 2.7 2.0 1.4 0.39 0.07 0.0036 3 2.3 4.4 3.0 2.1 1.4 0.38 0.07 (a) x 2.1 4.2 2.9 2.2 1.5 0.41 0.09 0.0048 85

σ 0.2 0.2 0.2 0.2 0.2 0.05 0.03 0.0016

1 7.2 10.9 10.1 9.1 7.8 2.78 0.09 0.0003 2 4.4 8.4 8.4 7.2 4.8 2.77 0.27 0.0050 3 5.4 9.9 8.7 7.1 5.3 3.27 0.18 (a)

x 5.6 9.7 9.1 7.8 6.0 2.94 0.18 0.0027 270

σ 1.4 1.3 0.9 1.1 1.6 0.29 0.09 0.0033

1 6.8 8.9 9.0 7.9 6.0 3.46 0.11 0.0014 2 6.0 8.9 9.1 7.7 6.6 3.37 0.10 0.0010 3 4.9 7.5 7.7 6.5 5.2 3.29 0.09 (a)

x 5.9 8.4 8.6 7.4 5.9 3.37 0.10 0.0012 360

σ 1.0 0.8 0.8 0.8 0.7 0.08 0.01 0.0003

1 4.4 8.7 6.3 5.9 5.1 0.58 0.11 0.0013 2 3.4 7.2 4.8 4.0 3.1 0.57 0.11 0.0016 3 4.0 7.7 5.5 5.6 5.1 0.58 0.14 (a) x 3.9 7.9 5.5 5.2 4.4 0.58 0.12 0.0015 40 (c)

σ 0.5 0.8 0.8 1.0 1.1 0.01 0.02 0.0002

1 7.5 13.6 11.3 9.5 6.5 1.63 0.16 0.0010 2 9.9 15.9 14.6 11.9 8.0 2.18 0.22 0.0026 3 7.7 13.7 11.4 10.2 7.4 1.89 0.37 (a) x 8.4 14.4 12.5 10.5 7.3 1.90 0.25 0.0018 85 (c)

σ 1.4 1.3 1.9 1.2 0.7 0.28 0.11 0.0011

1 12.6 18.7 16.8 14.6 10.1 1.99 0.11 0.0015 2 9.1 15.1 14.3 12.1 8.2 1.74 0.16 0.0021 3 11.4 15.3 15.5 13.1 8.8 2.42 0.08 (a) x 11.0 16.4 15.5 13.2 9.0 2.05 0.11 0.0018 115 (c)

σ 1.8 2.0 1.3 1.2 1.0 0.34 0.04 0.0004
1 (b) (b) (b) (b) (b) 2.70 0.10 <0.0001 2 (b) (b) (b) (b) (b) 2.43 0.15 0.0021 3 (b) (b) (b) (b) (b) 2.29 0.08 (a) x - - - - - 2.47 0.11 0.0011 135 (c)

σ - - - - - 0.21 0.03 - (a) Only two tests planned (b) Test not planned (c) Cyclic flow minute volumeE-10 BlankF-1 APPENDIX F

ESTIMATION METHOD FOR CYCLIC FLOW PENETRATIONSF-2 F.1 Introduction

The results summarized in Section 3.5 demons trated that the mean inhalation flow is a key parameter when comparing penetrations measured under constant and cyclic flow
conditions. To further understa nd the relationship, a method was developed to predict cyclic flow penetrations based on penetr ations measured over a range of constant flow rates. The method is described in Section F.2 and compared to the experimental results that were discussed
in Section 3.0.

F.2 Approach

Initially, the effect of flow rate on pene tration for a specific particle size must be determined experimentally. A regression analysis of this data provides the penetration as a
function of flow rate:

B ) ( C C i F A F P × =
where P i is the penetration of the specific particle size (%), F C the constant flow rate (L/sec), and A and B the regression coefficients. An exam ple is provided in Figure F-1 for the SEA P100 cartridge tested against a 0.2 μ m particle at flow rates of 42.5, 135, and 180 L/min. For cyclic flow, the flow rate through the filter is time depe ndent and, thus, the penetration will also be time dependent. Assuming sinusoidal flow, the time de pendent flow rate F( t) is given by: ⎟ ⎠ ⎞ ⎜ ⎝ ⎛

= t

F t F Peak ω π 2 sin ) (

where F Peak is the peak inhalation flow rate (L/sec), ω is the breathing flow cycle time (sec), and t is the time (sec). The flow rate over the inhala tion cycle is provided in Figure F-2 for the four cyclic flow conditions used in cartridge testi ng. Combining the above expressions gives the penetration as a function of time over the inhalation cycle:

B 2 sin )) ( ( ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ × = t F A t F P Peak

i ω π

which is shown in Figure F-3 for each of the four flow conditions.F-3 y = 0.0011x 2.8267

R 2 = 0.9989

0.0001

0.001

0.01

0.1

1

0.1 1 10 Flow Rate (L/sec)Penetration (%) 0.2 um

Figure F-1. Effect of Flow Rate and Pa rticle Size on Measured Penetration Through the Survivair ® P100 Cartridge

0 50 100 150 200 250

0 0.2 0.4 0.6 0.8 1 1.2 1.4 T ime ( sec) 0.8 L, 25 breaths/min 1.15 L, 37 breaths/min 1.35 L, 42 breaths/min 1.55 L, 44 breaths/min

Figure F-2. Instantaneous Flow Rates During Inhalation Cycle Assuming Ideal Sinusoidal Waveform B ) ( )) ( ( t F A t F P i

i × =F-4 0.E+00 1.E-02 2.E-02 3.E-02 4.E-02 5.E-02 6.E-02 7.E-02 8.E-02 9.E-02 1.E-01

0 0.2 0.4 0.6 0.8 1 1.2 1.4 T ime ( sec) 0.8 L, 25 bpm 1.15 L, 37 bpm 1.35 L, 42 bpm 1.55 L, 44 bpm

Figure F-3. Predicted Instantaneous Penetrat ions During Inhalation Cycle Based on Measured Constant Flow Penetrations for the SEA Cartridge

The average penetration over the inhalation cycle was then determined for each cyclic flow condition using the following expression:



# ∫ ∫

= 2

0 2

0 )) ( (

π π

dt dt t F P P i

Avg

The integral was estimated using a numerical technique. The predicted cyclic flow penetrations using this method are compared with the measured cyclic flow penetrations measured for the cartridges and filtering facepieces in Figures F-4 and F-5. The figures include a variety of particle sizes and flow conditions. The flow ra tes in the legend repres ent cyclic flow minute
volumes. The dashed line is the one-to-one line, and represents agreement between the predicted and measured penetrations. The results show that the penetration measured during breathing flow conditions can be accurately estimated from the constant flow conditions, as all data points
tend to lie on the one-to-one line.F-5 0.0001 0.001 0.01 0.1

1 10 100

0.0001 0.001 0.01 0.1 1 10 100 Predicted Penetration (%)Measured Penetration (%)

SEA P100 (0.1, 0.2, 0.3 um) Survivair P100 (0.1, 0.2, 0.3 um) North N95 (0.1, 0.3, 0.7 um) MSA N95 (0.1, 0.3, 0.7 um)
1:1 Line

Figure F-4. Comparison of Measured and Predicted Cyclic Flow Penetrations Through Cartridges

0.001

0.01

0.1

1 10 100

0.001 0.01 0.1 1 10 100 Predicted Penetration (%)Measured Penetration (%)

MSA N95 (0.02 to 0.3 um) Gerson N95 (0.02 to 0.3 um) Moldex P100 (0.02 to 0.3 um) 3M P100 (0.02 to 0.3 um)

Figure F-5. Comparison of Measured and Predicted Cyclic Flow Penetrations Through Filtering FacepiecesF-6 BlankG-1 APPENDIX G

MICROBIOLOGICAL METHODSG-2 G.1 Bg Spores

G.1.1 Growth/Harvest of Bg

The Bg spores were purchased from the U.S. Army's Dugway Proving Ground (Dugway, UT) in powder form.

G.1.2 Quantification of Bg Spores

The concentration of Bg spores was determin ed by the standard plate and count method. Samples collected on mixed cellulose ester filters were removed from their respective filter holders using decontaminated forceps and plac ed in 50 mL conical t ubes containing 10 mL pH=7.4 phosphate buffered saline (PBS). Extrac tion was then performed by vortexing each tube at the maximum setting for 30 seconds each. Bg samples were serially diluted in PBS per standard microbiological protocols. Samples were then plated in triplicate on Tryptic Soy Agar (TSA) using the Spiral Biotech Autoplate ® 4000 (Figure G-1). The plates were incubated overnight at 30 ° C. Colony forming units per mL (cfu/mL) were determined by counting the resulting colonies with the Spiral Biotech QCount ® colony counter Figure G-2.

Figure G-1. Spiral Biotech Autoplate 4000 ®G-3 Figure G-2. Spiral Biotech QCount ® Colony Counter

G.2 MS2 Phage

G.2.1 Growth of E. coli

E. coli serves as the host for MS2 replic ation and was needed for the MS2 quantification assay. Before cu lturing, the E. coli (American Type Culture Collection [ATCC] No. 15597, Rockville, MD) stock was tested for pur ity by streaking on a tryptic soy agar (TSA) plate, incubating at 37°C for 12 hours, and exam ining the plate for contaminating colonies. After verifying the stock was pure, a working so lution of E. coli was prepared by inoculating nutrient broth (NB) media and incubating in a sh aking incubator at 37°C and 150 revolutions per minute (rpm).

G.2.2 Growth/Harvest of MS2

MS2 was prepared according to the U.S. Army Dugway Proving Ground Draft SOP: MS2 Growth and Purification (March, 1996) . Two 50 mL overnight cultures of Escherichia coli
A/ λ in LB-Miller broth were prepared by inocul ating each 50 mL aliquot of LB-Miller in 250 mL flasks with one colony each of E. coli A/ λ . The cultures were incubated approximatelyG-4 12 hours at 37 ° C with shaking at 200 rpm. After th e incubation period was complete, each
50 mL culture was used to inoculate 500 mL of LB-Miller broth in 2800 mL fernbach flasks.
The cultures were incubated at 37 ° C until a cellular density of 10 8 to 10 9 cells was achieved indicated by an optical density at 600 nm of 0.2 to 0.3. Once this density was achieved, each
culture was inoculated with 3 mL of a 5.0E+11 pfu/mL MS2 suspension to achieve a multiplicity of infection of approximately 0.5. The cultures were incubated at 37 ° C with shaking at 200 rpm until lysis occurred, which was indicated by a drop in optical density. To aid in release of phage from the cells, 500 μ L of 0.05 g lysozyme/mL was added to each culture and incubated at 37 ° C with shaking at 200 rpm for 30 minutes. After the incubation, 1.0 mL of 0.5 M EDTA and
1.0 mL of chloroform were added to each culture and incubated at 37 ° C with shaking at 200 rpm for 30 minutes. The suspensions were then centrifuged at 8000 rpm at 4 ° C for 30 minutes in 250 mL centrifuge bottles to remove cell debris . The supernatant was filtered through a 0.22 μ m cellulose acetate filter. This crude preparation was stored at 2 - 8 ° C. The MS2 phage stock solution was from the ATCC (No. 15597-B1). MS2 was grown by adding 0.1 mL of the MS2 stock and 0.2 mL of the E. coli working solution to 3 mL of molten top agar and then pouring the mixture onto a TSA pl ate. Plates were incubated for 24 hours at a temperature of 37°C to allow virus growth. Afte r incubation, 3 mL of filtered, de-ionized water was added to plates which had 10 3 to 10 4 plaques and the surface of th e plate agitated for five minutes to facilitate transfer of MS2 from the agar to the water. The liquid was removed from the plates, centrifuged at 8000 rpm for 15 minutes and filtered through a 0.2 μm filter to remove any cellular debris. MS2 remained in suspensi on throughout centrifugation and filtration. This clarified virus suspension became the worki ng solution for bioaerosol generation and its infectivity was determined as described in sec tion G.2.4. Previous experience has shown that this working solution will have > 10 9 infectious virus particles per mL of solution. A precipitation procedure was used to furt her purify the crude MS2 preparations. The crude MS2 suspensions were added to a sterile 2 000 mL flask containing a sterile stir bar.
Sodium chloride was added to a final concentrat ion of 0.5 M (29.2 g/L). Polyethylene glycol 8000 was added to a final concentration of 10% ( 100 g /L). The suspension was stirred at the lowest setting for 12 hour s while incubating at 4 ° C. The precipitation suspension was then centrifuged in 250 mL centrifuge bottles at 10,000 rpm for 30 minutes at 4 ° C. The resultingG-5 supernatant was discarded and the pellets were resuspended in one liter of 0.22 μ m-filtered distilled water. This purified su spension was the stored at 2 – 8 ° C.

G.2.3 Dry MS2 Preparation

Dry MS2 was prepared by adding 500 mL of the purified MS2 suspension to 500 mL of 20% skim milk solids. The resulting susp ension was mixed thoroughly and divided equally among three 500 mL bottles. The MS2 suspensions were then frozen at -70 ° C for three hours. The surface area of the MS2 was maximized by incuba ting the bottles at a slant during freezing. The frozen MS2 suspensions were then placed uncapped in freeze flasks and connected to a Labconco Lyph-Lok 6 freeze dry system. The sample s were dried for 6 days. After the samples were completely dry, they were removed from the lyophilizer and large pieces were broken up with a spatula. Particle size was further reduced by light grinding with a mortar and pestle. The dry MS2 was then placed in a US Stoneware milling jar with 16 pieces of 0.5 inch milling media. The milling jar was placed on an automated roller and the MS2 was milled for three hours. The dry MS2 was removed from the milling jar and stored in a sterile Nalgene bottle. Final particle size reduction was achieved using a jet mill (M odel 00 Jet-O-Mizer, Fluid Energy Processing and Equipment Company, Telford, PA) operated at 120 psig. The crude MS2 was fed to the jet mill using an electromagnetic vibrating feeder (Model F-TO-C, FMC Technologies, Homer City, PA). The feed material to the jet mill is entrai ned by the stream of circul ation fluid within the jet mill. The violent jet action breaks up individual pa rticles through particle to particle impaction. The jet mill is shown in Figures G-3 and G-4. After milling, the dry MS2 was mixed with 10 percent Aerosil by weight.G-6 Figure G-3. Jet Mill Used for Processing Dry MS2

Figure G-4. Jet Mill and Vibrating Feeder Used for Processing Dry MS2

G.2.4 Enumeration of MS2

The number of infective virus pa rticles was determined by pla que assay. Plaque assays are done by infecting a monolayer of host cells. When light is passed through a Petri dish containing a monolayer of cells th e dish appears cloudy. As the virus grows and lyses the host, the area where cells are dying becomes clear. This is called a plaque. Ideally, the virus sampleG-7 is diluted so that each plaque is made by a single virus particle a nd the concentration of infectious virus in a sample is given as the number of pfu per mL of solution. Sampled gelatin filters were removed fr om their respective filter holders using decontaminated forceps and placed in 50 mL c onical tubes containing 10 mL pH=7.4 phosphate buffered saline (PBS). The filters we re then solubilized by incubating at 37 ° C with shaking at 200 rpm for 15 minutes. MS2 samples were then serially diluted in PBS per standard microbiological protocols and pl ated following the method desc ribed by U.S. Army Dugway Proving Ground Draft SOP: MS2 Growth and Purifi cation (March, 1996). Using this method, a 0.1 mL aliquot of diluted MS2 suspension was tran sferred to an empty Pe tri dish, along with a 0.2 mL aliquot of Escherichia coli A/ λ host cells in the logari thmic phase of growth. Approximately 20 mL of TSA with a decreased per centage of agar (0.75%) was then poured into each dish and the contents were thoroughly mixed. Each sample was plated in triplicate and the plates were incubated overnight at 37 ° C. Plaques, areas of clearing caused by lysis of the E.coli host cell lawn, were counted and used to calcula te the plaque forming units per mL (pfu/mL).G-8 BlankH-1 APPENDIX H

SHAKEDOWN TESTING OF THE BIOAEROSOL TEST SYSTEMH-2 H.1 Bioaerosol Test System Shakedown

Prior to efficiency testing, shakedown testing was performed to establish proper operating conditions. This included inert test ing to compare with the ECBC test system, characterization of the challenge aerosol, flow calibrations, and characte rization of the viable particle samplers. The system shakedown results are provided in this Appendix.

H.2 Comparison with ECBC Test System

An objective of this task is to compare efficiencies measured using the inert and biological aerosols. Since the inert testing was performed at ECBC and the biological testing at Battelle, shakedown tests were performed with inert aerosols to compare the two test systems. Inert testing was completed at Battelle with th e North N95 cartridge filter and challenge aerosols
of 0.3 and 1.0 μ m PSL. The upstream and downstream con centrations were measured using the LAS-X. The results are provide d in Table H-1 and gr aphically compared in Figure H-1. In general, the measured penetrati ons at both facilities were sim ilar with the exception of the
1.3 μ m results at a constant flow of 180 L/min. The penetration m easured at Battelle under these conditions was approximately an order of magnit ude higher than that measured at ECBC. The trends in measured penetration are similar for both facilities.

Table G-1. Comparison of Inert Filtration Efficiencies Measured at Battelle and ECBC

Filter Particle Size ( μ m) Flow Condition Flow Rate (L/min) Average Penetration (%) ECBC Penetration (%) North N95 0.3 Constant 42.5 1.6 ± 0.04 1.0 ± 0.02 North N95 0.3 Constant 180 13 ± 2.8 10 ± 0.02 North N95 1.3 (a) Constant 42.5 0.03 ± 0.04 0.03 ± 0.01 North N95 1.3 (a) Constant 180 0.3 ± 0.06 0.06 ± 0.01 North N95 0.3 Cyclic 42.5 (b) 3.9 ± 2.7 3.5 ± 1.7 North N95 0.3 Cyclic 68 (c) 4.3 ± 6.2 7.5 ± 1.0 North N95 1.3 (a) Cyclic 42.5 0.08 ± 0.02 0.06 ± 0.05 North N95 1.3 (a) Cyclic 68 0.05 0.05 ± 0.03 (a) 1.0 um PSL used in Battelle testing (b) 1.15 L tidal volume, 37 breaths/min (c) 1.55 L tidal volume, 44 breaths/minH-3 0.001 0.01 0.1

1 10 100

Constant - 42.5 L/min Constant - 180 L/min Cyclic - 42.5 L/min Cyclic - 68 L/minPenetration (%) ECBC - 0.3 um Battelle - 0.3 um ECBC - 1 um Battelle - 1 um

Figure H-1. Comparison of In ert Filtration Efficiencies Measured at Battelle and ECBC

H.3 Challenge Aerosol Characterization

Shakedown testing was completed to measure the size distribution of the Bg spores and to verify the generator maintained a stable output . The aerosol concentrati on as a function of test duration as measured by the Aerosizer is shown in Figure H-2. The bi oaerosol particle size
distributions were measured usi ng either a laser aerosol spectrometer, Aerosizer, or cascade impactor as was described in the report. Attempts to measure the particle size distributions of the bioaerosols using the Andersen impactor were unsuccessful due to the high challenge
concentration which resulted in overloading of the stages.H-4 1.00E+07 1.00E+08 1.00E+09 1.00E+10

0 5 10 15 20 25 30 35 40 45 Time (min)Concentration (#/m3)

Figure H-2. Concentration of Bg Spore Aeroso l Challenge as a Function of Test Time

H.4 Bioaerosol Sampling

Tests were completed to characterize the coll ection efficiencies of the cellulose ester
filters. The collection efficiencies were measur ed by collecting samples with two filters operated in series and performing a bioassay on each. The initial filter typi cally collected over 99.99 percent of the total spores collected. Tests were also completed w ithout a respirator filter to compare samples collected upand downstream. Tests were performed at c onstant flow rates of 42.5 and 180 L/min and resulted in measured penetrations of 97.3 and 93.3 percent, respectively. Similar tests at cyclic
flows with minute volumes of 40 and 135 L/min resu lted in penetrations of 93 and 103 percent. Thus, the upstream and downstream measurements were within 10 percent for all tests. Following a test with a Bg spore challenge , the test system was flushed with HEPA filtered air and a negative control test was performed. Samples were collected from the downstream chamber and bioassayed. No viable pa rticles were detected. This demonstrated the procedure for sterilization of the system and 47-mm filter holders was successful and there was no carryover between tests. The minimum detect ion limit of the bioassay technique was set at 20 cfu or pfu/L air sampled. A typical challenge concentration was 1 x 10 5 cfu/L air sampled. Thus, the minimum measurable penetration was t ypically 0.005 percent. This was nearly an order-of-magnitude lower than the P100 pe netration requirement (<0.03 percent).I-1 APPENDIX I

SUMMARY OF BIOAEROSOL PENETRATION RESULTSI-2 Table I-1. Summary of Measured Pe netrations through SEA HE-T

Bioaerosol Challenge Bg "Wet" Bg "Dry" MS2 "Wet" MS2 "Dry" Flow Rate (L/min) Trial Penetration (%) 1 <0.005 <0.001 <0.002 <0.001 2 <0.003 <0.001 <0.004 <0.001 3 <0004 <0.001 <0.001 - x 0.004 0.001 0.002 0.001 42.5 Constant

σ 0.001 - 0.002 -

1 <0.004 <0.002 <0.013 <0.001 2 <0.004 <0.003 <0.008 <0.002 3 <0.004 <0.003 <0.005 - x 0.004 0.003 0.009 0.002 135 Constant

σ - 0.001 0.004 0.001

1 <0.001 <0.005 <0.001 <0.001 2 <0.001 <0.002 <0.013 <0.001 3 <0.003 <0.001 <0.006 - x 0.002 0.003 0.007 0.001 42.5 Cyclic (a)

σ 0.001 0.002 0.006 -

1 <0.001 <0.001 0.015 <0.002 2 <0.002 <0.002 <0.010 <0.005 3 <0.003 <0.002 <0.020 - x 0.002 0.002 0.015 0.004 67.5 Cyclic (a)

σ 0.001 0.001 0.005 0.002 (a) Cyclic flow minute volume

Table I-2. Summary of Measured Pe netrations through Survivair 1050

Bioaerosol Challenge Bg "Wet" Bg "Dry" MS2 "Wet" MS2 "Dry" Flow Rate (L/min) Trial Penetration (%) 1 <0.004 0.008 0.059 <0.030 (b) 2 <0.003 <0.001 0.005 <0.002 3 <0.002 <0.001 0.002 - x 0.003 0.003 0.022 0.002 42.5 Constant

σ 0.001 0.004 0.032 -

1 <0.005 0.086 <0.008 <0.001 2 <0.004 <0.002 0.035 <0.002 3 <0.004 <0.002 <0.012 - x 0.004 0.030 0.018 0.002 135 Constant

σ 0.001 0.048 0.016 0.001

1 0.001 <0.002 0.017 <0.008 2 0.002 <0.003 <0.007 <0.001 3 0.001 <0.001 <0.012 - x 0.001 0.002 0.012 0.005 42.5 Cyclic (a)

σ 0.001 0.001 0.005 0.005

1 <0.001 <0.003 <0.047 <0.015 2 0.006 <0.003 0.013 <0.009 3 0.013 <0003 <0.32 (b) - x 0.006 0.003 0.030 0.012 67.5 Cyclic (a)

σ 0.006 - 0.024 0.004 (a) Cyclic flow minute volume (b) Not included in average due to low challenge concentrationI-3 Table I-3. Summary of Measured Pene trations through MSA Flexi-Filter

Bioaerosol Challenge Bg "Wet" Bg "Dry" MS2 "Wet" MS2 "Dry" Flow Rate (L/min) Trial Penetration (%) 1 <0.002 <0.001 1.4 <0.001 2 <0.002 0.012 0.24 <0.016 3 <0.002 <0.001 0.012 - x 0.002 0.005 0.55 0.009 42.5 Constant

σ - 0.007 0.75 0.010

1 <0.004 0.013 2.7 0.010 2 0.006 0.018 0.80 0.004 3 0.005 0.011 0.43 - x 0.005 0.014 1.3 0.007 135 Constant

σ 0.001 0.004 1.2 0.004

1 0.003 0.014 1.0 <0.002 2 <0.002 0.010 0.16 <0.004 3 <0.003 0.014 2.1 - x 0.003 0.013 1.1 0.003 42.5 Cyclic (a)

σ 0.001 0.002 1.0 0.002

1 0.003 0.036 0.68 0.022 2 0.080 0.017 0.81 0.029 3 0.019 0.037 0.13 - x 0.034 0.030 0.54 0.025 67.5 Cyclic (a)

σ 0.041 0.011 0.36 0.005 (a) Cyclic flow minute volume (b) Low challenge, not included in average

Table I-4. Summary of Measured Penetrations through North 7506

Bioaerosol Challenge Bg "Wet" Bg "Dry" MS2 "Wet" MS2 "Dry" Flow Rate (L/min) Trial Penetration (%) 1 0.008 0.003 0.39 0.001 2 <0.004 0.003 0.32 0.002 3 <0.003 0.012 0.19 - x 0.005 0.006 0.30 0.001 42.5 Constant

σ 0.003 0.005 0.10 0.001

1 0.009 0.16 0.78 0.022 2 <0.005 0.018 2.1 0.021 3 0.013 0.042 2.9 - x 0.009 0.074 1.9 0.022 135 Constant

σ 0.004 0.075 1.1 0.001

1 0.004 0.030 0.53 0.004 2 0.010 0.026 4.0 0.007 3 0.004 0.110 0.54 - x 0.006 0.055 1.7 0.005 42.5 Cyclic (a)

σ 0.004 0.047 2.0 0.002

1 0.021 0.039 1.0 0.006 2 0.013 0.023 4.3 0.018 3 0.008 0.035 2.1 - x 0.014 0.032 2.5 0.012 67.5 Cyclic (a)

σ 0.007 0.001 1.7 0.009 (a) Cyclic flow minute volumeI-4 Table I-5. Summary of Measured Penetrations through 3M 8293

Bioaerosol Challenge Bg "Wet" Bg "Dry" MS2 "Wet" MS2 "Dry" Flow Rate (L/min) Trial Penetration (%) 1 <0.003 0.018 <0.001 <0.002 2 <0.003 <0.003 <0.001 <0.002 3 <0.003 <0.001 <0.001 - x 0.003 0.008 0.001 0.002 85

σ - 0.009 - -

1 <0.008 <0.002 <0.012 <0.004 2 <0.012 <0.003 <0.014 <0.004 3 <0.009 <0.004 <0.015 - x 0.010 0.003 0.014 0.004 270

σ 0.002 0.001 0.002 -

1 <0.009 <0.002 <0.004 <0.005 2 <0.004 <0.001 <0.001 0.014 3 <0.003 <0.001 <0.001 - x 0.005 0.001 0.002 0.009 85 (a)

σ 0.003 0.001 0.002 0.006

1 <0.005 <0.001 <0.001 <0.003 2 <0.007 <0.001 <0.001 <0.002 3 <0.003 0.008 <0.008 - x 0.005 0.003 0.003 0.003 135 (a)

σ 0.002 0.004 0.004 0.001 (a) Cyclic flow minute volume (b) Low challenge, not included in average

Table I-6. Summary of Measured Penetrations through Moldex 2396

Bioaerosol Challenge Bg "Wet" Bg "Dry" MS2 "Wet" MS2 "Dry" Flow Rate (L/min) Trial Penetration (%) 1 0.056 0.034 0.008 <0.004 2 <0.008 0.004 <0.002 <0.004 3 <0.004 0.015 0.006 - x 0.023 0.017 0.005 0.004 85 Constant

σ 0.029 0.015 0.003 -

1 <0.007 <0.004 0.057 <0.005 2 0.015 0.004 0.043 <0.003 3 <0.014 <0.005 0.051 - x 0.012 0.004 0.050 0.004 270 Constant

σ 0.004 0.001 0.007 0.001

1 0.008 <0.001 <0.002 <0.002 2 0.005 <0.001 <0.001 0.026 3 0.007 0.006 0.001 - x 0.006 0.003 0.001 0.014 85 Cyclic (a)

σ 0.002 0.003 0.001 0.017

1 0.010 <0.002 0.014 <0.007 2 <0.006 0.001 0.013 <0.002 3 0.010 0.007 <0.003 - x 0.009 0.003 0.010 0.004 135 Cyclic (a)

σ 0.002 0.003 0.006 0.04 (a) Cyclic flow minute volumeI-5 Table I-7. Summary of Measured Penetr ations through MSA Affinity Plus

Bioaerosol Challenge Bg "Wet" Bg "Dry" MS2 "Wet" MS2 "Dry" Flow Rate (L/min) Trial Penetration (%) 1 0.25 0.016 0.64 0.010 2 0.12 0.069 0.10 <0.004 3 0.008 0.019 0.80 - x 0.13 0.035 0.51 0.007 85 Constant

σ 0.12 0.030 0.37 0.004

1 0.071 0.029 3.0 0.011 2 0.11 0.059 0.35 0.006 3 0.28 0.038 0.34 - 4 0.075 - - - x 0.13 0.042 1.7 0.009 270 Constant

σ 0.099 0.016 1.8 0.004

1 0.19 0.087 0.18 0.028 2 0.52 0.18 0.89 0.016 3 0.48 0.13 1.6 - 4 0.19 - 1.1 - x 0.35 0.13 0.93 0.022 85 Cyclic (a)

σ 0.18 0.048 0.60 0.009

1 0.032 0.13 1.2 0.060 2 0.021 0.52 0.31 0.10 3 0.069 1.28 1.1 - 4 0.065 - 1.8 - x 0.047 0.64 1.1 0.082 135 Cyclic (a)

σ 0.024 0.59 0.61 0.030 (a) Cyclic flow minute volume (b) Low challenge, not included in average

Table I-8. Summary of Measured Penetrations through Gerson 1730

Bioaerosol Challenge Bg "Wet" Bg "Dry" MS2 "Wet" MS2 "Dry" Flow Rate (L/min) Trial Penetration (%) 1 0.062 0.034 0.30 0.028 2 0.022 0.030 0.72 0.40 3 0.024 0.020 - - x 0.036 0.028 0.51 0.22 85 Constant

σ 0.023 0.007 0.30 0.27

1 0.39 0.25 1.6 1.0 2 0.22 0.22 1.3 0.037 3 0.60 0.12 2.4 - x 0.40 0.20 1.8 0.52 270 Constant

σ 0.18 0.064 0.55 0.69

1 0.28 0.096 0.43 0.60 2 0.13 0.13 0.77 6.8 (b) 3 0.24 0.36 0.53 - x 0.21 0.20 0.48 0.60 85 Cyclic (a)

σ 0.077 0.14 0.07 -

1 0.17 0.32 0.90 0.099 2 0.30 1.6 0.35 0.051 3 0.30 5.2 1.4 - 4 - - 0.89 - x 0.26 2.4 0.89 0.075 135 Cyclic (a)

σ 0.074 2.5 0.43 0.034 (a) Cyclic flow minute volume (b) Probable leak in seal to system, not included in averageI-6 BlankJ-1 APPENDIX J

SUMMARY OF REAEROSOLIZATION RESULTSJ-2 Table J-1. Summary of Reaerosolization Trials with 0.8 μ m PSL Aerosol

Filtering Facepiece Loading Collection Filter

Filter Type Trial Density (#/cm 2 ) Number (#) PreCough

(#) PostCough

(#) Reaerosolization (%) Average (%) St Dev 1 1.3x10 4 2.2 x10 6 0 3 0.0001 2 1.7x10 4 3.0 x10 6 12 66 0.002 MSA Affinity Plus (No Valve) 3 - - - - - 0.001 0.001

1 1.4x10 5 2.4 x10 7 350 200 0.0008 2 1.4x10 5 2.5 x10 7 95 205 0.0008 MSA Affinity Plus (No Valve) 3 1.6x10 5 2.8 x10 7 0 75 0.0003 0.0006 0.0003

1 8.2x10 5 1.4 x10 8 20 175 0.0001 2 8.2x10 5 1.4 x10 8 50 700 0.0005 MSA Affinity Plus (No Valve) 3 8.2x10 5 1.4 x10 8 145 1070 0.0007 0.0005 0.0003

1 1.8x10 4 2.8 x10 6 35 200 0.007 2 2.5x10 4 3.9 x10 6 50 362 0.009 MSA Affinity Plus

(With Valve) 3 1.7x10 4 2.6 x10 6 58 150 0.006 0.007 0.002

1 1.4x10 4 2.4 x10 6 25 65 0.003 2 1.5x10 4 2.6 x10 6 100 70 0.003 Gerson 1730 (No Valve) 3 2.4x10 4 4.1 x10 6 25 85 0.002 0.003 0.0003

1 3.3x10 4 4.9 x10 6 410 600 0.012 2 4.6x10 4 7.0 x10 6 30 775 0.011 Gerson 1740 (With Valve) 3 2.9x10 4 4.3 x10 6 15 120 0.003 0.009 0.005

1 2.2x10 4 3.4 x10 6 15 145 0.004 2 2.5x10 4 3.8 x10 6 25 155 0.004 Gerson 1740 (Valve Protected During Loading) 3 2.2x10 4 3.3 x10 6 165 130 0.004 0.004 0.0002

Table J-2. Summary of Reaerosolization Trials with 2.2 μ m PSL Aerosol

Filtering Facepiece Loading Collection Filter

Filter Type Trial Density (#/cm 2 ) Number (#) PreCough

(#) PostCough

(#) Reaerosolization (%) Average (%) St Dev 1 1.7x10 3 2.9 x10 5 85 20 0.006 2 2.7x10 3 4.6 x10 5 35 35 0.008 Gerson 1730 (No Valve) 3 2.1x10 3 3.6 x10 5 30 50 0.015 0.009 0.005

1 1.9x10 3 2.9 x10 5 130 20 0.006 2 1.7x10 3 2.5 x10 5 80 35 0.014 Gerson 1740 (With Valve) 3 2.1x10 3 3.2 x10 5 35 52 0.016 0.012 0.005J-3 Table J-3. Summary of Reaerosolization Trials with Bg Spore Aerosol

Filtering Facepiece Loading Collection Filter

Filter Type Wet/Dry Tria l Density (#/cm 2 ) Number (#) PreCough

(#) PostCough

(#) Reaerosolization (%) Average (%) St Dev 1 9.2x10 2 1.6x10 5 100 55 0.034 2 9.0x10 2 1.6x10 5 262 60 0.037 MSA Affinity Plus (No Valve) Wet 3 - - - - - 0.035 0.002

1 6.8x10 2 1.2x10 5 20 55 0.046 2 6.8x10 2 1.2x10 5 10 25 0.019 MSA Affinity Plus

(With Valve) Wet 3 6.5x10 2 1.1x10 5 10 60 0.054 0.040 0.018

1 1.2x10 3 2.1x10 5 30 140 0.065 2 2.2x10 3 3.8x10 5 30 170 0.045 Gerson 1730 (No Valve) Wet 3 1.0x10 3 1.8x10 5 35 105 0.058 0.056 0.012

1 3.8x10 2 2.4 x10 6 8 115 0.18 2 8.0x10 2 2.6 x10 6 0 20 0.012 Gerson 1740 (With Valve) Wet 3 - - - - - 0.094 0.13

1 1.2x10 4 2.1 x10 6 - 2670 0.13 2 - - - - - Gerson 1730 (No Valve) Dry 3 - - - - - 0.13 -

1 1.5x10 4 2.3 x10 6 - 3550 0.16 2 - - - - - Gerson 1740 (With Valve) Dry 3 - - - - - 0.16 -

Table J-4. Summary of Reaerosolization Trials with MS2 Phage Aerosol

Filtering Facepiece Loading Collection Filter

Filter Type Wet/Dry Tria l Density (#/cm 2 ) Number (#) PreCough

(#) PostCough

(#) Reaerosolization (%) Average (%) St Dev 1 1.1x10 4 2.0 x10 6 1090 765 0.038 2 1.7x10 4 2.9 x10 6 35 3610 0.124 MSA Affinity Plus (No Valve) Wet 3 1.7x10 4 2.9 x10 6 175 1050 0.035 0.066 0.050

1 9.3x10 3 1.5 x10 6 1300 890 0.06 2 8.9x10 3 1.5 x10 6 0 300 0.02 MSA Affinity Plus

(With Valve) Wet 3 1.1x10 4 1.7 x10 6 610 4300 0.3 0.11 0.12

1 1.8x10 4 1.3 x10 6 35 200 0.007 2 2.5x10 4 1.6 x10 6 50 362 0.009 Gerson 1730 (No Valve) Wet 3 1.7x10 4 2.2 x10 6 58 150 0.006 0.007 0.002

1 7.8x10 4 1.3x10 7 730 42,000 0.32 2 6.8x10 4 1.1x10 7 0 61,000 0.53 Gerson 1730 (No Valve) Dry 3 6.4x10 4 1.0x10 7 60 59,000 0.54 0.46 0.13

1 4.1x10 4 6.2x10 6 1900 43,000 0.69 2 1.3x10 4 2.0x10 6 960 9,700 0.49 Gerson 1740 (With Valve) Dry 3 8.9x10 3 1.3x10 6 880 4,500 0.30 0.51 0.18FIRST CLASSDEPARTMENT OF THE ARMYCDR USARDECOMATTN AMSRD CII5183 BLACKHAWK ROADAPG MD 21010-5424OFFICIAL BUSINESS