1

Efficiency of Respiratoor Filter Media Against Nano-Aerosols

Seong Chan Kim* and David Y.H. PuiUniversity of Minnesota

2/20

1) This research was funded by NIOSH (National Institute for

Occupational Safety and Health) and CFR (Center for Filtration

Research), and the filter media used in this study was made by

Hollingsworth and Vose Company, 3M Company, Lydall Inc.,

W.L. Gore and Donaldson.

2) The findings and conclusions in this research have not been

formally disseminated by NIOSH and should not be construed

to represent any agency determination or policy.

Acknowledgement & DisclaimerAcknowledgement & Disclaimer

3/20

1) Nanoparticles are being manufactured from a wide range of materials to determine their unique properties and potential forindustrial applications. The combination of specific material properties and extremely small size might result in health problems if manufactured nanoparticles enter into the body.

2) It is important to study the performance of filtration media using nanoparticles to determine the filtration requirements of personal protective equipment (PPE) or air ventilation system.

3) Two opposing filtration theories:Increasing efficiency with decreasing size by Brownian deposition Possible decreasing efficiency with decreasing size due to thermal rebound

4) In this study, a nanoparticle filtration test system has been established, and filtration tests of a very wide range of filter media have been conducted with silver nanoparticles (3 ~ 20 nm).

BackgroundBackground

4/20

0.0E+00

2.0E+05

4.0E+05

6.0E+05

8.0E+05

1.0E+06

1.2E+06

1 10 100Particle Diameter (nm)

Par

ticle

Cou

nt (#

)

850 C900 C950 C

Silver ParticlesFurnace flow: 3 lpmUCPC 3025A

Nanoparticle penetration test systemNanoparticle penetration test system

5/20

Hollingsworth and VoseFiberglass Media

HE Approaches HEPA Regime for small DP

HF is More Common to Standard HVAC Systems

Hollingsworth and VoseFiberglass Media

HE Approaches HEPA Regime for small DP

HF is More Common to Standard HVAC Systems

Filtration Parameters HE 1073 HE 1021 HF 0031 HF 0012Thickness Ave. 0.053 0.069 0.074 0.074(cm) %COV 2.3 4.3 2.3 2.3

Basis Weight Ave. 63.9 80.3 82.6 69.2(g/m^2) %COV 0.53 0.67 0.86 0.92

Pressure Drop Ave. 8.4 4.7 3.5 1.3at 5.3 cm/sec (mmH2O) %COV 1.48 1.35 1.94 1.47

DOP % Penetration Ave. 12.8 39 45.8 79.9.3 µm at 5.3 cm/sec %COV 2.2 1.7 0.92 1.24

Fiber Density 2.4 2.4 2.4 2.4(gm/cm^3)

Solidity 0.05 0.049 0.047 0.039

Effective Fiber Diameter 1.9 2.9 3.3 4.9(µm) (Rubow)

Effective Fiber Diameter 2.1 3.2 3.7 5.4(µm) (Davies)

Effective Pore Diameter 8.8 13.4 16.1 26.2(µm) (Benarie)

Media

Specifications of H&V fiberglass filter mediaSpecifications of H&V fiberglass filter media

6/20

SEM image of H&V filter media (X500)SEM image of H&V filter media (X500)

HE1073 HE1021

HF0031 HF0012

7/20

0.0001

0.001

0.01

0.1

1

10

100

1 10 100

Particle Size (nm)

Pen

etra

tion

(%)

HF0012HF0031HE1021HE1073

H&V filter mediaUCPC 3025AFace Velocity: 5.3 cm/sSilver NanoparticlesFurnace Temp: 870 ºC

NP penetration for H&V filter media (5.3 cm/s)NP penetration for H&V filter media (5.3 cm/s)

8/20

0.0001

0.001

0.01

0.1

1

10

100

1 10 100

Particle Size (nm)

Pen

etra

tion

(%)

HF0012HF0031HE1021HE1073

H&V filter mediaUCPC 3025AFace Velocity: 10 cm/sSilver NanoparticlesFurnace Temp: 870 ºC

NP penetration for H&V filter media (10 cm/s)NP penetration for H&V filter media (10 cm/s)

9/20

0.0001

0.001

0.01

0.1

1

10

100

1 10 100

Particle Size (nm)

Pen

etra

tion

(%)

HF0012HF0031HE1021HE1073

H&V filter mediaUCPC 3025AFace Velocity: 15 cm/sSilver NanoparticlesFurnace Temp: 870 ºC

NP penetration for H&V filter media (15 cm/s)NP penetration for H&V filter media (15 cm/s)

10/20

Nano-sized Particle Percent Penetration Comparison for FourFiberglass Filter Papers: U of MN Test (Silver Particles) and

3M Company TSI 8160 (NaCl Particles)* at 10 cm/s

0.0001

0.001

0.01

0.1

1

10

100

1 10 100 1000

Particle Diameter (nm)

% P

enet

ratio

n

Filter A - U of MN TestFilter A - TSI 8160Filter B - U of MN TestFilter B - TSI 8160Filter C - U of MN TestFilter C - TSI 8160Filter D - U of MN TestFilter D - TSI 8160

* Research conducted by Center for Filtration Research, University of MN, presented by S-C. Kim and L. Franklin at 27th CFR Review Meeting, April 2005. Fiberglass filter paper donated by Hollingsworth and Vose.

Comparison with 3M’s test results (20~300 nm)Comparison with 3M’s test results (20~300 nm)

11/20

GORE® Membrane FilterMedia F

Highly Charged Blown Fiber (fine-Df)

Media D

Highly Charged Blown Fiber (mid-Df)

Media B

HEPA Paper, Grade 3398F-SMedia E

Split Film FiberMedia C

Corona Charged Blown Fiber (mid-Df)

Media A

TypeName

Commercial filter media for NP penetration testCommercial filter media for NP penetration test

12/20

SEM images of commercial filter media (1)SEM images of commercial filter media (1)

Media A Media B

Media C

13/20

SEM images of commercial filter media (2)SEM images of commercial filter media (2)

Media D Media E

Media F

14/20

0.0001

0.001

0.01

0.1

1

10

1 10 100Particle Size (nm)

Pen

etra

tion

(%)

Media CMedia BMedia AMedia DMedia F

UCPC 3025AFace Velocity: 5.3 cm/sSilver NanoparticlesFurnace Temp: 900 °C

NP penetration for commercial filters (5.3 cm/s)NP penetration for commercial filters (5.3 cm/s)

15/20

0.0001

0.001

0.01

0.1

1

10

1 10 100 1000

Particle Diameter (nm)

Pene

tratio

n (%

)

Media A (3M)Media B (3M)Media C (3M)Media D (3M)Media E (3M)Media A (UMN)Media B (UMN)Media C (UMN)Media D (UMN)

NIOSH Filters(Univ. of Minn.)Silver NanoparticlesUCPC3025AFace Velocity: 5.3 cm/s

Comparison with 3M’s test results (20~300 nm)Comparison with 3M’s test results (20~300 nm)

16/20

All measurements taken at 20 fpm (= 10 cm/s), 0.78 micron latex particles.Efficiency and pressure drop are for the composite (substrate + fine fiber)

0.01621.36Sample D

0.05958.84Sample B

0.0094.28Substrate

0.03138.40Sample C

0.11880.01Sample A

Pressure drop (in. H2O)

Efficiency (%)

Specifications of nanofiber filtersSpecifications of nanofiber filters

17/20

Sample A Sample B

Sample C Sample D

SEM images of nanofiber filter mediaSEM images of nanofiber filter media

18/20

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 5 10 15 20 25 30 35 40 45

Face velocity (cm/s)

Pre

ssur

e dr

op (i

n H

2O)

Sample ASample BSample CSample DSubstrate

Pressure drop of nanofiber filter mediaPressure drop of nanofiber filter media

19/20

1

10

100

1 10 100 1000

Particle Size (nm)

Pen

etra

tion

(%)

Sample A (Silver NP)Sample B (Silver NP)Sample C (Silver NP)Sample D (Silver NP)Substrate (Silver NP)Sample A (NaCl)Sample B (NaCl)Sample C (NaCl)Sample D (NaCl)Substrate (NaCl)Donaldson (780 nm PSL)

Donaldson Nanofiber Filter

Test particles: Silver nanoparticlesCarrier Gas; Nitrogen (4lpm)Furnace Temp. #1: 1150˚CFurnace Temp #2. 1000˚CFace Velocity: 20ft/sec (10 cm/s)Particle counter TSI 3025A UCPCSample Time: 60sec

NP penetration for nanofiber filters (10 cm/s)NP penetration for nanofiber filters (10 cm/s)

20/20

1) A nanoparticle filtration test system has been established.

2) Filtration tests were conducted with silver nanoparticles (3 ~ 20 nm) for a wide variety of flat filter samples, including fiberglass papers, commercial filter media and nanofiber filter media.

3) Filtration efficiencies increased with decreasing particle size for all of the tested filter media. No significant evidence of nanoparticle thermal rebound was observed. The data follows the well-known trends of classical Brownian deposition filter theory.

4) Future work should be done to use this data to develop a nanoparticle filtration model, taking into consideration of fibrous filter structure, particle charge, fiber charge, air temperatureand face velocity.

Conclusions & future workConclusions & future work

21

Thanks for your attention!!!

&

Questions?Test system

H&V filter & Results

Commercial filter & Results

Nanofiber filter & Results