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Bacterial suspension preparation and sample pretreatment of medical mask bacterial filtration efficiency tester

Author:QINSUN Released in:2023-08 Click:88

Medical Mask Bacterial Filtration Efficiency Tester is a test equipment independently developed and produced by our company, Qisnun Precision Electromechanical Technology Co., Ltd. The bacterial filtration efficiency of daily protective masks such as medical surgical masks and civilian masks, and the melt-blown fabric used in the production of masks is suitable for performance testing of the bacterial filtration efficiency of masks by metrology and verification departments, scientific research institutions, mask manufacturers and other related services.

Applicable standards:

YY0469-2011, Q/0212 ZRB003-2011, ASTMF2100, ASTMF2101, EN 14683

Preparation of the bacterial suspension:

Take the fresh broth culture of third generation Staphylococcus aureus, dilute it with a 1.5 phosphate buffer solution% containing peptone to prepare the bacterial concentration of 5.0 × 105 cfu/mL suspension.

Sample pre-treatment:

Place the mask meltblown fabric sample in an environment with a temperature of (21±5)°C and a relative humidity of (85 ± 5)% before testing Pre-treatment lasts at least 4 hours and each company takes three samples from the same batch.

Bacterial filtration efficiency test:

① According to the YY0469-2011 test of medical surgical mask standard, the two sampling ports of the Henderson pipeline of the detector of the BFE system were connected to the Anderson six-stage sampler.

②Place the 90mm diameter sample plate into the Anderson six-stage sampler. The sampler gas flow is controlled at 28.3 L/min, the peristaltic pump flow is 0.180 mL/min, and the liquid feed time is set to 1 min. The timeps is set to 2 min, system cleaning time is set to 1 min, and a positive quality control is tested prior to testing.

③ After sample testing is complete, retest the positive quality control. Next, draw an air sample from the aerosol chamber for 2 minutes as a negative quality control, during which time the bacterial suspension cannot be delivered to the nebulizer.

④ Place the agar plate upside down and place it in an incubator at (37±2)°C for (48±2) h. Colony units (positive wells) formed by bacterial particle aerosols were then counted and converted to the possible number of impacted particles using the positive well conversion table.

Formula for calculating bacterial filtration efficiency: BFE=(C-T)/C×100% (where C: the average value of the positive quality control; T: the sum of the samples), \"Technical Requirements for Medical Surgicalal Masks\" (YY 0469-2011) states that the bacterial filtration efficiency should be greater than 95%.