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ASTM F2101

Evaluating the Bacterial Filtration Efficiency (BFE) of Medical Face Mask Materials

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ASTM F2101: Assessing Bacterial Filtration Efficiency of Medical Face Masks

ASTM F2101 outlines the method for measuring the bacterial filtration efficiency (BFE) of medical face mask materials. This test method measures the bacterial filtration efficiency (BFE) of medical face mask materials, employing a ratio of the upstream bacterial challenge to downstream residual concentration to determine the filtration efficiency of medical face mask materials.

BFE is a quantitative test method for filtration efficiency that can determine a maximum efficiency of up to 99.9%. ASTM F2101 BFE can also be employed to measure the bacterial filtration efficiency of other porous medical products such as surgical gowns, surgical drapes, and sterile barrier systems.

Generally, colony-forming units are used for raw units of bacterial efficiency. Colony-forming units are then converted to percentages of bacterial efficiency for medical face masks.

ASTM F2101 Test Methods and Requirements:

  • Test organism: Staphylococcus aureus is a bacteria, that forms a part of our normal body flora and acts as an opportunistic human pathogen. Staphylococcus aureus is the leading cause of infections contracted within the hospital and hence used for BFE testing.
  • BFE testing introduces aerosolized bacteria into an aerosol chamber using a nebulized culture suspension of 5 × 10^5 CFU/mL Staphylococcus aureus.
  • The Staphylococcus aureus aerosol is drawn through the medical face mask material within the aerosol chamber by a vacuum attached to the cascade impactor.
  • Perform a positive control run without a test specimen clamped into the test system to determine the number of viable aerosol particles generated.
  • The aerosol’s mean particle size (MPS) is calculated from the results of these positive control plates.
  • For testing, a medical face mask material sample is clamped between a six-stage cascade impactor in an aerosol chamber.
  • After cascade impactor sampling, the agar plates are incubated for a period of 48 hours.
    After incubation, the number of viable particles collected on each of the six-stage plates of the cascade impactor is counted.
  • The bacteria collected from the agar plates are quantified using traditional bacterial efficiency units (CFU) and then converted into a percentage to represent filtration efficiency.
  • The bacterial challenge solution is nebulized at approximately 1700 to 3000 viable particles per test to determine the correct CFU units of bacterial efficiency.
  • The challenge delivery rate is based on the results of the positive control plates when the aerosol is collected with no test material specimen clamped into the testing system.
  • Perform a negative control sample by collecting a 2-minute air sample from the aerosol chamber. No bacterial challenge should be pumped into the nebulizer while collecting the negative control sample.
  • Incubate agar plates at 37± 2 °C for 48 ± 4 h.

Importance Of ASTM F 2101

Evaluating the Bacterial Filtration Efficiency (BFE) of medical face mask materials is crucial for ensuring that these barriers effectively prevent the transmission of bacteria, thereby safeguarding both healthcare workers and patients from potential infections. This assessment is not only vital for adhering to health and safety regulations but also plays a pivotal role in maintaining a sterile environment in medical settings. By verifying the performance of mask materials through BFE testing, manufacturers can enhance product reliability and consumer trust, ultimately contributing to improved public health outcomes.

Why choose Microbe Investigation (MIS)?

At Microbe Investigation Switzerland (MIS), we specialize in face mask testing, adhering to the stringent requirements of ASTM F2101. This standard is critical for evaluating the bacterial filtration efficiency of medical face masks, ensuring they meet the highest safety standards.

Our team of experts excels in adapting methodologies to align with specific product designs and chemical compositions, ensuring accurate and precise results.

In addition to our standard testing services, we offer bespoke solutions tailored to the unique needs of our clients.

To get a quote for ASTM F2101 and to enquire about our testing services, please get in touch with our expert and get a free consultation.


ASTM F2101 describes the procedure for measuring the bacterial filtration efficiency (BFE) of materials used in medical face masks.

Medical face masks can be tested with ASTM F2101.

ASTM F2101 test takes 5-6 weeks to complete.

The test specimen is challenged with Staphylococcus aureus to perform the test.

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