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 F2101–14. 

 

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The risk of occupational exposure of health professionals to infections caused by various agents, especially viruses and bacteria, has become a threat to them, since in their activity they must manipulate biological fluids that may contain pathogens. The biological risk is ubiquitous and of wide variety, since it can be blood, air, oral or contact.

This risk is not only for health professionals, involved in the treatment and care of injured or sick people, but also for patients. The diseases they can cause can be generated by a wide variety of biological agents that can pose significant risks to life and health. Therefore, it is important to reduce contact with air that may contain pathogens through the use of medical masks.

This test method evaluates the efficiency of bacterial filtration, for medical masks, using a relationship between the bacterial exposure introduced by an upper air stream and the residual concentration in the lower air stream to determine the effectiveness of the materials used. to prevent the spread of the pathogen. The test method, in addition to being applied to medical masks, can also evaluate the bacterial filtration efficiency of other porous medical products such as surgical gowns, surgical drapes and sterile barrier systems (excluding respirators), primarily evaluating the performance of the materials used, but not their design.

The organism used as an aerosol in this test method is Staphylococcus aureus, which is frequent in the normal flora of the body, but which is also a human pathogen and an important cause of nosocomial infections.

The material under evaluation in the test is positioned between an aerosolization chamber and a six-stage cascade impactor. In the aerosolization chamber, the culture suspension of Staphylococcus aureus is introduced and dispersed using a nebulizer. The aerosol droplets that impact with the medical mask are collected throughout the six stages of the process. Both positive and negative controls are incorporated into the test. Negative controls determine the aerosol counts introduced by the upper current.

In this way, the relationship between the counts present in the upper current generated by the nebulizer is evaluated with respect to the counts obtained in the lower current after having passed the mask, reporting the percentage of efficiency of the bacterial filtration exerted by the material evaluated. The method does not define acceptable levels of bacterial filtration efficiency.

The tests can be carried out with the aerosol exposure directed both through the facial side (in contact with the person's skin) or from the external side (external to the person), of the material under test, allowing to evaluate the efficiencies of filtration that are related both to the aerosols generated by the patient, and to the aerosols generated in the environment. Unless otherwise specified, the test will be performed with the inside (facial side) of the medical mask.

Degradation due to physical, chemical and thermal situations could negatively affect the performance of the medical mask material. The integrity of the material can also be compromised during use by effects such as bending and abrasion, or by moistening with contaminants such as alcohol and perspiration. The test without taking into account these situations could lead to a false assertion of security. Therefore, the performance of the medical mask material for the efficacy of bacterial filtration can be evaluated by following suitable pretreatment procedures that are representative of the conditions expected during its use.

The customer must choose whether or not to precondition the material to be tested and how to proceed if necessary. In addition, you must indicate the area of ​​the material that you want to evaluate, if not the inner (facial) area of ​​the mask.