FILTRATION EFFICIENCY: THE DIFFERENCE BETWEEN BFE, PFE, & VFE
By now, you’re probably all too familiar with what it is like to wear a facemask. After the outbreak of COVID-19, these personal protective equipment (PPE) items are far more common than ever before.
However, not all masks are created equal. Some industries, such as the medical and dental fields, require materials that are stronger and more effective in filtering out bacteria and germs than others. Furthermore, industrial settings with an enhanced risk of exposure to specific particulates (toxic dusts, mold spores, etc.) require a higher level of protection, too.
Through a special process called filtration efficiency testing, masks are given ratings that help determine the strength of the materials and how effective it is at protecting a wearer from inhaling a certain particle. This gives the wearer an idea of the level of protection they’re receiving when wearing a mask.
Here is what you need to know about filtration efficiency testing and the three most common types.
What is Filtration Efficiency?
Filtration efficiency is essentially the rating at which one type of material filters out particles. This test method is typically performed on specific types of textiles used in personal protective equipment (PPE), including face masks, protective coveralls, medical gowns, air filters, and much more. Additionally, there are certain types of tests that help establish how the material holds up in a specific environment.
These tests are incredibly common and necessary to ensure that specific materials hold up to the situations in which the end-user could be at risk. By buying facial masks and other barrier equipment that has been tested, you can rest assured in knowing that your employees, patients, workers, and other individuals are safe.
Why do Filtration Efficiency Tests Matter?
So, why do these tests even matter? In order to protect the wearer from the transmission of diseases, deadly viruses, and harmful particulates that can cause serious respiratory damage or other ailments, manufacturers need to know how well their product works.
Furthermore, filtration efficiency tests are also used to determine the overall protection of the skin in items like coveralls, gowns, or other medical clothing. Essentially, the process is designed to ensure that microscopic elements don’t end up passing through the cloth barrier and harming the wearer.
Having these ratings ensures that companies that manufacture PPE sell products that truly protect the wearer and perform as they are designed to against the common hazards in their work environment.
What Industries Commonly Use This Type of Testing?
To understand what industries use this type of testing, you must be acquainted with the three primary test categories. PPE manufacturers use this testing to determine the effectiveness of products, while the companies that purchase the items select products based on their individual ratings.
Common industries that use products with requirements for specific filtration efficiency levels include all medical fields, dental fields, veterinary care, manufacturing, construction, industrial, energy sectors, and more.
Different Types of Filtration Efficiency Testing
Of course, not all the tests are the same. There are multiple ways in which a manufacturer can test a textile to determine its filtering capabilities. However, for the purpose of this guide, we are covering the three most common filtration efficiency tests: the bacterial filtration efficiency test, the particle filtration efficiency test, and the viral filtration efficiency test.
What Does Bacterial Filtration Efficiency (BFE) Mean?
Bacterial filtration efficiency testing assesses how well a particular material filters out bacteria. It is used to determine compliance with specific standards including ASTM F2100, ASTM F2101, and EN 14683. This is the basic standard for the type of material used in medical-grade face masks.
During a BFE test, a part of the fabric is securely clamped between a special cascade impactor and an aerosol chamber. A specific bacterium, usually staphylococcus aureus, is added to the aerosol chamber and is then drawn through the mask using a vacuum.
Test personnel then check the number of bacterial colonies that have passed through the material. This test is repeated several times to determine a comparative average of how the fabric performs. The material is then given a rating based on the test results. Generally, BFE measures how well a material protects against live bacteria particles that measure from one to five microns.
What is PFE (Particle Filtration Efficiency)?
Particle filtration efficiency (PFE) is essentially the same concept as BFE, but the tests are performed differently.
Instead of bacteria, the material is tested against an aerosol of a specific particulate, such as a harmful fume, dust, or other airborne particulates. Non-living bacteria are sometimes used, as well. Generally, a high-level PFE material blocks non-viable particles ranging in size from 0.1 microns to one micron.
After several tests, researchers then determine how well the material filtered out or blocked the substance. The better the filtration ability, the higher grade the mask material receives.
PFE standards aren’t usually as strict as medical-grade tests, but they are still incredibly important. Most industrial respirators, filters (HEPA: High-Efficiency Particulate Air [Filter]), and face masks are at the very least held to specific PFE standards and/or ratings.
What is VFE (Viral Filtration Efficiency)?
Viral filtration efficiency (VFE) is nearly identical to PFE and BFE. The biggest difference is that a specific virus is used in aerosol form instead of bacteria or particulates.
VFE is exceptionally important in high-grade medical masks when blocking out viruses like COVID-19, influenza, and others is incredibly crucial.
Why have a separate form of VFE instead of just using BFE? The two tests generally go hand-in-hand, with VFE being the lesser-used approach. Generally, a material that does well during the BFE test will also perform high on the VFE test.
What Are the ASTM Standards for Filtration Efficiency Tests?
While there are many different companies that offer this type of testing across the globe, the exact process of the tests can vary from one lab to another. However, to ensure all manufacturers follow the same guidelines, there are certain ASTM standards that must be followed when working with a certain type of PPE.
Most commonly, this is referred to as ASTM F2100. ASTM is an organization that sets specific standards for various industries and products. Their overall goal is to make products more effective, and thus safer for the user.
When it comes to barrier rates, there are three classifications for ASTM standards.
- ASTM Level One: Ideal for basic medical procedures and events where no splashes, sprays, or other fluid exposure are expected.
- ASTM Level Two: Best for situations or procedures where there’s a moderate level of fluid exposure or spray expected.
- ASTM Level Three: Situations where there is a high risk of fluid spray or exposure expected.
Generally, most high-grade medical masks and PPE fall into the ASTM Level Three category. However, there might be times when a lighter grade mask, such as an ASTM Level One or ASTM Level Two would be more appropriate.
Usually, ASTM Level One masks are used for patients and visitors, which are basically the same paper face mask you might use at the dentist. ASTM Level Two/Three Masks are used for sterile environments, such as surgeries and wound care. (It is also important to note that most medical professionals see little difference between an ASTM Level Two mask and an ASTM Level Three mask.)
Finally, there’s the N-95 mask which provides an even higher level of protection than an ASTM Level Three material. These are generally worn in situations where exposure to an aerosol transmitted disease, like COVID-19 or tuberculosis, is expected.
What About COVID-19?
After the coronavirus pandemic first started, you might remember that there was a huge demand for N-95 masks. The reason why an ASTM Level mask wouldn’t be appropriate in a medical setting is that it simply does not filter aerosol particles as well as an N-95.
However, in an open area with minor exposure risk, such as what the general public experiences while at the grocery store or out in ordinary life, an ASTM Level One to Three mask would still offer a fairly decent level of protection against the COVID-19 virus.
Wrap Up: What is Filtration Efficiency?
Filtration efficiency is designed to ensure specific textiles meet the filtration needs in certain environments. In more casual terms, it tests how well certain items protect a wearer from bacteria, particulates, and viruses within a given situation.
It is important for giving manufacturers a standard to adhere to, while also letting wearers understand the exact effectiveness of the specific type of mask or coverall they’re wearing.
When shopping for quality PPE products like medical face masks, it is important to pay attention to these types of ratings. Often, this will give you a good idea of the overall effectiveness of a specific mask.
Are you ready to learn more about the various types of face masks and other PPE items in our inventory? Please contact our team and International Enviroguard today for details.