Scope:

The standard method ASTM F2101 specifies a test for determining Bacterial Filtration Efficiency (BFE) of medical face mask materials. The testing principle is to subject the face side of the mask to an aerosol containing droplets of 3.0-microns size inoculated with Staphylococcus Aureus,at a prescribed flow rate that corresponds to normal human respiration. BFE is computed from the ratio of upstream bacterial challenge to downstream residual concentration. The ASTM F2101 test method also permits testing with the liner side of the face mask being subjected to bacterial challenge. The results of the test are useful in evaluating the protection offered by various specimens of medical masks against patient generated as well as externally generated bacterial aerosols. BFE values of medical masks are rated at ASTM levels 1,2 and 3, depending on the criticality of the application.

Test Procedure:

The apparatus broadly comprises a testing column with aerosol generator and liquid dosing pump on the top and detector at the bottom, with associated controls and instrumentation.

The ASTM F2101 specifies the following key requirements for the BFE test:

Aerosol type: Staphylococcus aureus bacteria in 3.0-microns size droplets with minimum particle count of 2200 ±500 viable particles per test.

Flow rate: 28 litres per minute

Aerosol detector: Six Stage Viable Particle Cascade Impactor

Test Time: 2 minute particle exposure per test

The specimens may be pre-conditioned by storage, flexing and abrasion, wetting with water or alcohol, to simulate realistic usage scenarios. or washing and folding. Since infectious organisms are involved, trained personnel shall conduct the test ensuring laboratory and personnel safety.

Sample size:

Medical face masks of standard size are subjected to the test.

Result:

The ASTM F2101 BFE value is reported as percentage efficiency at 3.0 micron for ASTM levels 1, 2, 3.