What are BFE and VFE, and why should I care?
What are BFE and VFE?
We see this written everywhere in connection with masks and respirators, and even with mask filters; everyone is talking about BFE and VFE. But what does it really mean? These are actually two different concepts, but both are important to understanding how good your mask or mask filter is.
BFE
This stands for Bacterial Filtration Efficiency. That means how well the mask or filter is able to block out incoming bacteria. Bacteria are microscopic organisms that live in soil, the ocean, inside the human gut and elsewhere. Some bacteria are good and help us out by doing things like curdling milk and yogurt, or helping us with our digestion. But other bacteria are destructive and cause nasty diseases like pneumonia or Staphylococcus aureus (MRSA). So a BFE test will tell us how much of this bacteria is blocked by a filter or mask. In this test, a Staphylococcus aureus aerosol is used. It's put through the filter in a constant flow. The results of this test are shown as a percentage; what percentage of the bacteria was blocked during the test. For example a surgical mask that is labelled BFE≥95% has been shown to block out at least 95% of the Staphylococcus aureus bacteria.
VFE
VFC is viral filtration efficiency; how well the filter or mask blocks virus particles. It is important to note that virus particles are much much smaller than bacteria particles, so in terms of dealing with the Coronavirus pandemic, the VFE of your mask or filter is extremely important. The Viral Filtration Efficiency (VFE) test follows the same procedure as BFE, except the aerosol test is done using the PhiX174 Bacteriophage DNA virus. Virus filtration efficiency can be reported up to >99.9% in a standard VFE test and up to >99.9999% in what is known as an 'increased challenge’ test.
So if you are looking to buy a mask filter or a respirator or even a simple surgical mask, you should keep an eye out for the BFE and VFE ratings. Masks that don't show ratings most likely have not been tested and certified, i.e., may or may not block the virus or even bacteria.