Healthcare work is hard and dangerous work. To become qualified and certified, doctors and nurses have to study for years and pass extremely difficult exams. The difficulties of health workers do not stop after they become qualified. They also tend to work long hours and are the frontline workers during pandemics. Although they didn't train to risk their lives and sometimes pay the ultimate price, they still perform the thankless task of nursing us to health. 

Because of the nature of their work, healthcare professionals are often near really sick people. And to avoid getting sick themselves, they must make use of protective gear. This is especially true during a public health crisis caused by a pandemic. Infectious diseases are no respecter of rank or knowledge, so doctors aren't impervious to harm. They must take appropriate measures to safeguard themselves from illness.

In healthcare, it's important to have the appropriate personal protective equipment (PPE) for doctors. And of all PPEs, the face mask is perhaps the most important. That's because it protects the two most important inlets to the body; the nose and the mouth. Most infectious diseases are either waterborne or airborne. And the most common way these kinds of illnesses enter the body is through the mouth or nose. 

Since there are different kinds of masks and they all offer different levels of protection, there is always a decision to be made. Healthcare professionals must choose the right kind of mask, and they must ensure that the chosen mask offers the right level of protection. However, it's not easy to make this choice. There are lots of different masks, and things like the level of protection and price must be considered before a choice is made. Of course, it may seem like common sense to just choose the mask that offers the highest level of protection. But healthcare professionals do not live in an alternate reality— they must also deal with pesky things like economics and supply. So they have to carefully gauge the threat they are dealing with, and then choose an appropriate mask to deal with it. 

First off, what criteria should be taken into account when choosing appropriate face masks? The FDA, the agency that oversees the production and certification of all surgical masks in America says that all masks must demonstrate performance in 4 areas. These areas are flammability, filter efficiency, fluid resistance and differential pressure.

It may seem like a simple task to choose a mask, but it's not. There are several nuances in design that make selecting a mask a somewhat difficult job. To have an idea of just how difficult it is to choose a mask, let's take a look at the different mask classifications. 

Mask Classifications

Procedure Masks

Procedure masks can be easily identified through the presence of two ear loops. These ear loops help secure the mask to the face. Procedural masks are usually used in isolation units, hospital grounds, and labour and delivery units. These masks may also be used in the emergency department, and could also be used in the intensive care unit. However, these masks may not be used in the operating room.

Surgical Masks

These masks are often used in the operating room, and they have two straps that secure the mask to the face, not loops. These masks are often used to protect against high-risk fluid exposure that could happen during surgery. After all, no one wants to get sprayed in the face with blood. 

Asides these two, there's also the surgical N95 respirator that's used to filter surgical smoke that is created by devices such as electrosurgical units, ultrasonic scalpels or dissectors. 

But even these masks must meet certain standards before they are certified. The Important question now is this; who sets the standard?

Who Sets The Standard?

Now, the FDA doesn't set the standards that these masks must meet to be certified. That is done by ASTM international. ASTM International, formerly known as American Society for Testing and Materials, is an international standards organisation that develops and publishes technical standards for a wide range of products. Which, of course, includes masks. 

Now, you may wonder why the FDA uses the standards of ASTM, a private organisation. Well, in 1995 the national technology transfer and advancement act was passed, and this act allows federal government agencies to use consensus standards developed by private organisations whenever possible. Other governments worldwide have also referenced ASTM standards.

 It's easy to see why ASTM standards are accepted globally. Right now, ASTM has published over twelve thousand standards over a wide range of industries. It has over thirty thousand members, over a thousand organisational members and members from about 140 countries. The organisation has about 140 technical committees and has several awards for contribution to standards authorship in the world. 

What Tests Do Masks Have To Go Through To Be Certified As Face Mask? 

There are four very important test phases that all surgical phase masks must go through before being certified by ASTM. These tests are as follows

  • Bacterial Efficiency Test
  • Particulate Filtration Efficiency
  • Mask Fluid Resistance Testing
  • Face Masks Pressure Differential 

Bacterial Efficiency Test

This test measures how well the medical mask filters out bacteria. To check this, the mask would be exposed to bacteria-containing aerosol. Bacteria droplets ranging from 0.1 to 0.3 microns will be used to check if the mask can filter out bacteria. For a mask to be called a surgical mask, it would have to filter out at least 95% of the bacteria it is exposed to. Masks of higher protection must have a filtration rate of at least 98%.

Particulate Filtration Efficiency

Viruses are way smaller than bacteria, so they may not be stopped the same way bacterias are stopped. That's why a particulate filtration efficiency test is important. The PFE measures how well a hospital mask can filter sub-micron particles (because these particles are the closest in size to viruses). Like the BFE, the PFE is measured in percentages. The higher the percentage, the better the mask can filter these particles. Testing for these particles is available from 0.1 microns to 5.0 microns. However, ASTM standards specify a test on 0.1-micron sub-particles. 

Mask Fluid Resistance Testing 

This test tries to measure how well the mask can minimize fluid that could transfer from the outer side of the mask to the inner side. This test also tests how well the mask can protect a wearer from the effects of a splash or spray. ASTM specifies testing with synthetic blood at different levels of pressure. These different levels of pressure are at 80, 120, 160 mm Hg to qualify for low, medium or high fluid resistance. 

These pressure levels aren't just arbitrary numbers either. The 120 mm Hg pressure represents arterial pressure, and the 160 mm Hg represents high-pressure irrigation. This level of pressure is what may occur during surgeries that include high-pressure irrigation. 

Face Masks Pressure Differential 

Also known as Delta P, Pressure Differential is a test that measures the flow resistance of the surgical mask. The test is often called an objective measure of breathability. The Delta P of a mask is measured in mm H2O/cm2 and the lower the value, the more breathable the mask is. The ASTM standard specifies that high to moderate barrier masks have a Delta P lower than 5 and that lower barrier masks must have a Delta P of 4.0 

Flame Resistance

Since hospitals contain substances that can accelerate fire spread, they must make use of fire-resistant materials. The ASTM standards specify that all surgical masks must be able to withstand exposure to flames for about three seconds. 

What Are The ASTM Standards Concerning Masks?

Like with kits of other technical equipment, ASTM has published standards concerning masks. And these are the standards that the FDA says masks must be classified according to. 

According to ASTM standard F2100-11, there are four levels of protection that masks offer. 

Minimum Level 

Minimum level masks are masks that are suitable for use as a simple barrier. They are good enough to be used for exams and short procedures that do not produce spray, fluid or aerosols. 

Level One 

Level one ASTM masks (or ASTM level one masks)  may be suitable for procedures where low amounts of fluid, spray, and/or aerosols are produced. For a mask to become an ASTM level one mask, it would have to meet several performance metrics across the board. 

The first is the fluid resistance performance check. An ASTM level mask must score at least 80 on that metric. The next is the bacteria and viral filtration efficiency test (BFE). The maximum filtration efficiency that can be determined by this test is about 99%. Any level 1 mask must score ≥ 95% on the test. After the BFE test is the Particle Efficiency Filtration Test that evaluates the particle retention or the filtration efficiency of the mask at sub-micron levels. The test measures the filtration efficiency of the mask using non-living particles that are about 0.1 microns in size. For a mask to meet ASTM level one mask, it must offer at least ≥95% protection against these particles.

The second to the last test is the Delta P metric— or differential pressure metric. This metric measures the airflow resistance of the mask and measures breathability. No matter how great a mask is, it's useless if it's impossible to breathe in. To test this, a controlled force of air is driven through the mask and the pressure on either side of the mask is measured. For a mask to be certified as an ASTM level one mask, it must have a <4.0 rating in this test. 

The last test is the flammability test. All ASTM rated masks, regardless of level, must at least have a class 1 rating.

Level Two Masks

ASTM level two masks are masks that are great for procedures where low to moderate amounts of fluid, aerosols or spray may be produced. ASTM level two masks must have fluid resistance rating of about 120, BFE rating of about ≥98%, PFE of the same,  and differential pressure rating of <5.0. 

Level Three

This is the highest level of protection any mask can offer. These sort of masks are ideal for procedures where moderate to heavy amounts of spray, fluid and aerosols are produced. ASTM level three masks must have a fluid resistance rating of about 160, BFE rating of about ≥98%, PFE rating of about ≥98%, and differential pressure of <5.0. 

How Do You Know The Ratings Of Masks

The next question is how do you choose the right masks for yourself? How do you know what ASTM rating each mask has? The answer is simple. All you need to do is check the packaging, and you'll have all the answers you want. The ASTM rating standard requires a graphic display on the packaging that states the performance level of the mask. 

Once doctors know the level of threat that they are exposed to daily, they will be able to make smart decisions on the kind of mask needed. A good example is the coronavirus pandemic. Once doctors knew that they needed the highest level of protection because of the nature of Covid-19, they were able to choose the N95 respirator— which is an ASTM level three rated face mask. 

What's the ASTM Level Three Mask

The ASTM level three mask is any mask that meets the level three criteria for masks set by the ASTM. Since the FDA uses the standards published by ASTM, most masks have to be rated at some ASTM level. The masks with the best protection are the ones that usually have the branded ASTM level three certification.