Choosing the Right Face Mask: 3 Things to Know

 

Rhysley

Protection is always preferred over preference. In today's scenario where on the one hand, we have a pandemic raging, with an effective vaccine still a distance away, safety is everyone's concern. There are various kinds of masks available in the market, and all masks are not the same. Keeping all the safety factors in mind for facial protection, one must ensure that the masks must satisfy the standards.

 

Choosing the Right Mask

It is primarily regarded that an ASTM rated mask is the right mask. The ASTM ratings make the process of choosing the right mask quite simple. One can select an ASTM-rated mask that gives the best protection, peace of mind and is perfect. When you are buying a mask, look for the ASTM Level 1/2/3 on the face mask package. Be careful. All face masks are not ASTM rated, making it imperative to make this critical check before buying a face mask.

What is ASTM?

Founded in 1898, ASTM International is one of the world's most extensive international standards developing organizations.  ASTM International develops and publishes technical standards for many products, materials, services, and systems. Worldwide, more than 12,800 ASTM standards are in use for safety and quality across a wide variety of industries and services worldwide, including ASTM F2100-11. Most of the healthcare organizations globally adopt ASTM recommendations to implement best practices. Since 2012, ASTM F2100-11 has been the standard for medical face masks.

Understanding ASTM Protection Levels

ASTM has a process in place to evaluate several characteristics, including sub-micron particulate filtration (PFE), bacterial filtration efficiency (BFE), differential pressure, and flame spread, and that determine whether a mask is of Level 1, 2, or 3. The primary difference between the three ASTM Protection levels is in the mask's resistance to penetration by synthetic blood. The minimum resistance pressure in a Level 3 mask is double that of a Level 1 mask.

 

• ASTM Protection Level 1: 

• This is for a low risk of fluid exposure.
• Low-Level Protection
• They are generally used for short procedures and exams that don't involve aerosols, spray, or fluid.
• ASTM Protection Level 2: 
• This is for moderate risk of fluid exposure
• Moderate Level Protection
• For low or moderate levels of aerosols, spray, or fluids.
• ASTM Protection Level 3: 
• Maximum Level Protection
• For high levels of aerosols, spray, and fluid.
• For high risk of fluid exposure 

US Food and Drug Administration, or simply FDA, is the organization that regulates medical devices in the USA. The standards have been drafted by the FDA, which serves as a benchmark for manufacturers to receive a license to sell their products in the market. These same standards also apply to surgical masks and other medical devices. FDA prescribes the measurement of filtration efficiency regarding inert particles and fire tests. 

ASTM F2100-11 is the standard specification for the performance of the material used in medical face masks.  The masks are classified into three levels. The performances of the materials composing the masks are evaluated by five tests - like bacterial filtration efficiency, splash resistance, breathability, particle filtration efficiency, and flammability test.

So, how will I know how each mask is rated?

In order to determine the rating of the face mask, one needs to simply look for ASTM Level 1, 2, or 3 on the package of the face mask. Since all face masks are not ASTM-rated, it's important to check before you choose to buy the mask. In order to ensure that one is getting the proper level of protection, it is worth the effort to find face masks that carry the ASTM rating.

How Are Face Mask Tested

Once the masks are manufactured, they should be tested to ensure their safety when used under different scenarios. All the masks are subjected to five related tests that they have to pass. 

1. Bacterial Filtration Efficiency in Vitro (BFE) – Test ASTM F2101

The effectiveness of a surgical mask is measured by its Bacterial Filtration Efficiency (BFE). The BFE test is performed on filtration materials, covers, fabrics, and devices designed to provide protection against biological aerosols. This test is a measure of a material's resistance to bacterial penetration. This test measures the percentage of bacteria larger than 3 microns filtered out by the mask. Staphylococcus aureus is the challenge material used to conduct the test. As part of the test procedure, aerosol with Staphylococcus Aureus bacteria is shot at the mask at 28.3 liters per minute. The effectiveness of the mask is measured in terms of the percentage of filtration efficiency. The percentage is calculated by dividing the total volume of the aerosol by the volume of the aerosol droplets blocked. The filtration efficiency depends on the size and number of the bacteria blocked and the amount of airflow. 

2. Particulate Filtration Efficiency (PFE) – Test ASTM F2299

PFE is another important parameter to measure the effectiveness of the mask. The Particle Filtration Efficiency test evaluates the nonviable particle retention or filtration efficiency of filter media at sub-micron levels. This test is performed on face masks and all filter material that allows only one cubic foot per minute (CFM) fluid flow to pass through it. This test for measuring the PFE is also known as the latex particle challenge. During the test, aerosol of polystyrene microspheres or latex is sprayed on the mask and the percentage of particles larger than 1 micron blocked by the mask is measured. 

3. Breathing resistance – Test MIL-M-36954 C: ΔP

Breathing resistance is measured to ensure that the mask retains its shape and has proper ventilation while the wearer breathes through it. The test aims to calculate the resistance to airflow of the face mask. It is tested by shooting a flow of air at the mask and then measuring the difference in air pressure on both sides of the mask. The breathing resistance is defined as the pressure difference divided by the surface area of the mask. When the breathing resistance is lower, the comfort level of the user is better. A differential pressure of less than 40 (Type I and II) and less than 60 (Type IIR) is required for surgical masks. The breathing resistance depends on a series of parameters such as the nature of the textile, the number of layers, thickness and the applied finish. 

4. Fluid Resistance – Test ASTM F1862

Fluid resistance, also known as the splash resistance test, is a synthetic blood resistance test for determining a fluid’s ability to act as a barrier to blood-borne pathogens. This test method offers a procedure for evaluating medical face mask resistance to synthetic blood penetration where a small volume about 2 ml of synthetic blood is passed at a high velocity of 80 mmHg, 120 mmHg, or 160 mmHg. It is useful in measuring the penetration resistance performance of medical face masks and ranking their performance. Medical face masks are used to prevent liquid penetration from the splashing of all kinds of body fluids, blood, and other potentially infectious materials. Depending on the visual evidence of synthetic blood penetration, the face mask passes or fails the test. 

5. Flammability – Test 16 CFR Part 1610: Flame Spread

The importance of the flammability test can be realized from the fact that there can be several flammable elements in a room that can easily cause and catch fire. The face masks are tested for their flammability by exposing it to a flame and then measuring how slowly it catches fire and how much time the material takes to burn. All three ASTM levels 1, 2, and 3 require the masks to be Class 1 flame resistant. 

ASTM F2100-11: Standard Specification for Performance of Materials Used in Medical Face Masks 

The table below summarizes the specific data required in order to be labeled an ASTM performance mask. 

TEST	LEVEL 1 BARRIER	LEVEL 2 BARRIER	LEVEL 3 BARRIER
ASTM F1862(Fluid Resistance in mmHg)	80	120	160
MIL-M-36954 C:  Delta P, ΔP mm H20/cm2(Breathability)	< 4	< 5	< 5
ASTM F2101: BFE (Filtration 3μm)	≥ 95%	≥ 98%	≥ 98%
ASTM F2299: PFE (Filtration 1μm)	≥ 95% @ 0.1 micron	≥ 98% @ 0.1 micron	≥ 98% @ 0.1 micron
16 CFR Part 1610: Flame Spread (Flammability)	Class 1	Class 1	Class 1

 

Does an ASTM-rated face mask provide all the protection I need?

In the healthcare environment, choosing the appropriate face mask is crucial in minimizing the spread of infectious diseases. However, choosing the correct mask is not a cakewalk considering the different options, prices, and brands that are available in the market. ASTM International is considered as one of the largest standards for the testing of face masks. 

ASTM rated masks protect one’s nose and mouth against splashes and sprays of blood and other bodily fluids, as well as bacteria and particulate matter of the sizes. Having said all that, it must be noted that the face masks do not provide respiratory protection against airborne diseases. For that purpose, a respirator such as N95, N99 is required.