ඔයාගෙ ටෙස්ටින් මෙතඩ් එක - ඉරට අල්ලලා බැලීම
මේකෙ ටෙස්ටින් මෙතඩ් එක:
Testing the Filtration Efficiency
A range of common household materials were tested, together with the material from a surgical mask (Mo ¨lnlycke Health Care Barrier face mask 4239, EN14683 class I), for comparison. Circular cutouts of the tested materials were placed without tension in airtight casings, creating a ‘‘filter’’ in which the material provided only barrier to the transport of the aerosol.
A Henderson apparatus allows closed-circuit generation of microbial aerosols from a Collison nebulizer at a controlled relative humidity. This instrument was used to deliver the challenge aerosol across each material at 30L/min using the method of Wilkes et al,2 which is about 3 to 6 times per minute the ventilation of a human at rest or doing light work, but is less than 0.1 the flow of an average cough.
Downstream air was sample simultaneously for 1minuteinto 10ml of phosphate buffer manucol antifoam using 2 all-glass impingers. One impinger sampled the microorganisms that had penetrated through the material filter, while the other sampled the control (no filter). The collecting fluid was removed from the impingers and assayed for microorganisms. This test was performed 9 times for each material. The filtration efficiency (FE) of the fabric was calculated using the following formula (cfu indicate colony-forming units):
FE = Upstream cfu - Downstream cfu x 100 / Upstream cfu
The pressure drop across the fabric was measured using a manometer (P200UL, Digitron), with sensors placed on either side of the filter casing, while it was challenged with a clean aerosol at the same flow rate.