ASTM F2101 - Standard Test Method for Evaluating the Bacterial Filtration Efficiency (BFE) of Medical Face Mask Materials, Using a Biological Aerosol of Staphylococcus aureus:
ASTM F2101 is a standardized test that evaluates the bacterial filtration efficiency (BFE) of medical face mask materials using a biological aerosol of Staphylococcus aureus. This test is used to quantitatively measure a mask material's ability to filter bacteria, with the highest efficiency determined by this method being 99.9%.
It's important to understand that the test does not define acceptable levels of bacterial filtration efficiency; therefore, specific testing conditions must be defined. The test is specifically designed to challenge mask materials with Staphylococcus aureus, a bacterium relevant for its role in nosocomial infections.
The test introduces a bacterial aerosol challenge to the mask materials at a flow rate of 28.3 L/mm, replicating the range of normal respiration. Unless specified otherwise, the inside of the mask is in contact with the bacterial challenge. It also allows for the aerosol challenge to be directed through either the face side or liner side of the test specimen. This setup allows for the evaluation of filtration efficiencies related to both patient-generated and wearer-generated aerosols.
ASTM F2101 acknowledges that degradation from physical, chemical, and thermal stresses may negatively impact mask performance. Factors such as flexing, abrasion, or contamination from substances like alcohol and perspiration may compromise material integrity. Therefore, it recommends testing under representative conditions if such factors are deemed significant. It also advises preconditioning to assess the impact of storage conditions and shelf life for disposable products, as well as the effects of laundering and sterilization for reusable ones.
When used for quality control, the test procedure encourages proper statistical design and analysis of large datasets, considering variables such as the number of individual specimens tested, average percent BFE, and standard deviation. Such comprehensive reporting helps establish confidence limits regarding product performance.
The scope of ASTM F2101 is limited and does not apply to all forms of biological aerosol exposure. The appropriateness of the test method should be evaluated for specific applications. Moreover, it evaluates mask materials as a piece of protective clothing, not as a respirator. Despite high BFE measurements, this does not necessarily guarantee wearer protection from biological aerosols as the test method primarily assesses material performance, not mask design, fit, or sealing properties.