Essential Test & Test Standards For Face Mask

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In previous blog I have shared about essential test and test standards for Face mask. Today we will talk about test one by one

Bacterial or Viral Filtration Efficiency (BFE/VFE)

It is also kind of Reparatory fit test.

To quickly and accurately detect the bacterial filtration efficiency (BFE) of various flat masks, 3D masks and protective materials.  Bacterial Filtration Efficiency (BFE) experimental method requires the development of a high-performance intelligent bacterial filtration efficiency detector.

The efficiency of the filtration medium is determined by comparing the colony count on the plates with and without the filtration medium in the aperture. The B.F.E. Test is widely used in medical products but is time consuming as it takes 24-48 hours to complete the test.

The procedure employs uniform microspheres in a latex which are suspended in an airstream and directed through the medium to be tested. The liquid in the airstream is removed from the airstream after passing through the medium, and a portion of the airstream is directed to a particle counter to count the particles in the airstream. By comparing the particles counted with and without the medium in the airstream, the efficiency of the medium can be determined.

1. A method of determining the filtration efficiency of a filtration medium comprising:
   • Suspending in an airstream a uniform latex of polymeric microspheres in water
   • Directing the suspended latex microspheres through an empty filter holder
   • Drying the airstream to remove the liquid portion of the latex
   • Directing a portion of the air stream through a particle counter to determine the number of particles in the air stream
   • Inserting a filtration medium in the filter holder
   • Directing the suspended latex microspheres through the filter holder containing the filtration medium
   • Drying the airstream to remove the liquid portion of the latex
   • Directing a portion of the air stream through a particle counter to determine the number of particles in the air stream; whereby the efficiency of the filtration medium can be determined by comparing the particles counted with the filtration medium in the filter holder and the particles counted without the filtration medium in the filter holder.
2. The method of claim 1 in which the microspheres are particles made from a polymer selected from the group consisting of polystyrene, polyvinyltoluene, copolymers of vinyltoluene and tertiary butylene, styrene and butadiene, styrene and vinyltoluene and styrene and divinylbenzene.
3. The method of claim 1 in which the microspheres have a diameter of from 0.6 to 2 microns.
4. The method of claim 1 in which the latex microspheres are directed through the filtration medium for a period of from 15 seconds to 120 seconds before the particles are counted by the particle counter.
5. The method of claim 2 in which the microspheres are polystyrene.