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Bacterial & Viral Filtration Efficiency (BFE/VFE)

The Bacterial Filtration Efficiency (BFE) test is performed on filtration materials and devices that are designed to provide protection against biological aerosols, such as face masks, surgical gowns, caps, and air filters.

This test is used for FDA 510(k) submissions for surgical masks, is required by ASTM F2100 and EN 14683, and complies with ASTM F2101 and EN14683. Nelson Labs staff assisted in the development of this test method, so we have more experience conducting this test than any other company. We can provide a one-stop shop for all ASTM F2100 and EN 14683 testing needs.

Applicable Standards

  • ASTM F2100
  • EN 14683
  • ASTM F2101

Testing Locations

  • Salt Lake City, UT, USA

Study Outline

Bacterial Filtration Efficiency (BFE)

The Bacterial Filtration Efficiency test determines the filtration efficiency by comparing the bacterial control counts to test article effluent counts. The test is conducted using Staphylococcus aureus as the challenge organism. After the filtration media is preconditioned for a minimum of four hours at 21 ± 5°C and 85 ± 5 % relative humidity, a liquid suspension of S. aureus is aerosolized using a nebulizer and delivered to the filtration media at a constant flow rate of 28.3 liters per minute (LPM) or 1 cubic foot per minute (CFM).

The aerosol droplets are drawn through a six-stage Andersen sampler for collection. The number of bacterial aerosol droplets contacting the filter media is determined by conducting challenge controls without filter medium in the test system. Challenge controls are maintained at 1700 – 2700 colony-forming units (CFU) with a mean particle size (MPS) of 3.0 ± 0.3 µm. This allows filtration efficiencies to be reported up to >99.9%.

The BFE test offers a number of advantages over other filtration efficiency tests. It has been used with little or no modification for years and provides a standard reference for comparison of filtration materials. The mean particle size can be tightly controlled and is sized using a six-stage viable-particle Andersen sampler, permitting stage-by-stage analysis. The BFE procedure is very reproducible, easily performed, and provides a more severe challenge to most filtration devices than would be expected in normal use. Large numbers of material can be evaluated in a relatively short time.

BFE testing is commonly performed along with the Differential Pressure (Delta P) test.

For housed filters, we recommend the Increased Challenge method. This procedure uses a higher concentration of challenge to be delivered to each test material. Filtration efficiency measurements can be determined up to >99.9999%.

Increased Challenge Bacterial Filtration Efficiency (BFE)

The Increased Bacterial Filtration Efficiency test determines the filtration efficiency by comparing the bacterial control counts to test article effluent counts. The test is conducted using Staphylococcus aureus as the challenge organism. A liquid suspension of S. aureus is aerosolized using a nebulizer and delivered to the filtration media at a constant flow rate of 30 liters per minute (LPM).

The aerosol droplets are collected in all-glass impingers (AGIs) in parallel. The challenge is delivered for a one-minute interval and sampling through the AGIs is conducted for two minutes to clear the aerosol chamber. The titer of the assay fluid is determined using standard plate count and/or membrane filtration techniques. The number of bacterial aerosol droplets contacting the filter media is determined by conducting challenge controls without filter media in the test system. Challenge controls are maintained at 1 x 106 colony-forming units (CFU) with a mean particle size (MPS) of 3.0 ± 0.3 µm. This allows filtration efficiencies to be reported up to >99.9999%.

The Increased BFE testing offers a number of advantages over other filtration efficiency tests. It has been used with little or no modification for years and provides a standard reference for comparison of filtration materials. The Increased BFE procedure is very reproducible, easily performed, and provides a more severe challenge to most filtration devices than would be expected in normal use.

Viral Filtration Efficiency (VFE)

The Viral Filtration Efficiency (VFE) test determines the filtration efficiency of a test article by comparing the viral control counts to test article effluent counts. The test is conducted using the bacteriophage phiX174 as the challenge organism. A liquid suspension of phiX174 is aerosolized using a nebulizer and delivered to the filtration media at a constant flow rate of 28.3 liters per minute (LPM) or 1 cubic foot per minute (CFM). The aerosol droplets are drawn through a six-stage Andersen sampler for collection.

The number of viral aerosol droplets contacting the filter media is determined by conducting challenge controls without filter media in the test system.

Challenge controls are maintained at 1700 – 2700 plaque-forming units (PFU) with a mean particle size (MPS) of 3.0 ± 0.3 µm. This allows filtration efficiencies to be reported up to >99.9%.

The VFE test offers a number of advantages over other filtration efficiency tests. The MPS can be tightly controlled and is sized using a six-stage viable-particle Andersen sampler, permitting stage-by-stage analysis. The VFE procedure is very reproducible, easily performed, and provides a more severe challenge to most filtration devices than would be expected in normal use. Large numbers of material can be evaluated in a relatively short time.

The VFE testing is commonly performed with the Bacterial Filtration Efficiency (BFE) test. For housed filters, we recommend the Increased Challenge method, which uses a higher concentration of challenge to be delivered to each test material. Filtration efficiency measurements can be determined up to >99.9999%.

Increased Challenge Virus Filtration Efficiency (VFE)

The Increased Viral Filtration Efficiency (VFE) test offers a number of advantages over other filtration efficiency tests. It has been used with little or no modification for years and provides a standard reference for comparison of filtration materials. The Increased VFE procedure is very reproducible, easily performed, and provides a more severe challenge to most filtration devices than would be expected in normal use.

The Increased VFE test determines the filtration efficiency by comparing the viral control counts to test article effluent counts. The test is conducted using the bacteriophage phiX174 as the challenge organism.

A liquid suspension of phiX174 is aerosolized using a nebulizer and delivered to the filtration media at a constant flow rate of 30 liters per minute (LPM). The aerosol droplets are collected in all-glass impingers (AGIs) in parallel. The challenge is delivered for a one-minute interval and sampling through the AGIs is conducted for two minutes to clear the aerosol chamber. The titer of the assay fluid is determined using a standard plate-count technique.

The number of viral aerosol droplets contacting the filter media is determined by conducting challenge controls without filter media in the test system.

Challenge controls are maintained at 1 x 106 plaque-forming units (PFU) with a mean particle size (MPS) of 3.0 ± 0.3 µm. This allows filtration efficiencies to be reported up to >99.9999%.

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If you have additional questions about Bacterial & Viral Filtration Efficiency (BFE & VFE) testing, or would like to consult with the experts at Nelson Labs, just send us a request or call us at (801) 290-7500.