Fundamentals of Medical Masks for Health Care Personnel 

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A recent webinar, entitled “PPE from A to Z: Decoding Masks,” provided an overview of medical face masks for health care personnel. Watch the webinar recording or read on to learn about the fundamentals of medical masks and best practices for medical professionals to keep yourself and your patients safe. 

What is a Medical Face Mask? 

A medical face mask is a loose-fitting, disposable device that creates a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment. It is meant to help block large-particle droplets, splashes, sprays, or splatter from reaching the wearer’s mouth and nose. As a method of source control, a medical face mask can also contain the wearer’s saliva and respiratory secretions from reaching others. This is the current definition provided by the U.S. Food and Drug Administration.

How is a Medical Face Mask Different from Other Face Coverings? 

Aside from medical face masks, there are two other forms of protective face coverings. Barrier face coverings are products worn on the face specifically covering at least the wearer’s nose and mouth with the primary purpose of providing source control and a degree of particulate filtration to reduce the amount of inhaled particulate matter. Respirators provide a tight seal against the skin and are designed to protect the wearer by filtering out hazardous airborne particles. Learn more.

How Have Medical Face Masks Changed Over Time? 

Over time, the situations in which a medical face mask is used have changed. Until the mid-1990s, medical face masks were used exclusively for patient protection. From the mid-1990s to 2020, the use of medical masks expanded to include their use as PPE for blood-borne pathogen protection. Since the initial wave of COVID-19, masks have been used to provide protection to the wearer although this is an area of performance that has been widely debated. 

The physical properties of medical face masks have also changed. Disposable (non-cloth) products gained greater acceptance with the availability of cheap disposable non-woven high-filtration materials. In addition, concern for HIV and Hepatitis exposure from infectious liquids led to fluid resistance requirements to protect the wearer. Shortages in PPE during the COVID-19 pandemic resulted in varying expectations for how medical masks function.

What Are the Types of Medical Face Masks? 

Different terms are used to refer to medical face masks: they may be labeled as surgical, isolation, procedure, or dental masks.

While there are no standardized definitions for these terms, surgical masks generally have separate ties as opposed to the more common ear loops that are found on isolation and procedure masks. The separate ties aid in better fitting the mask to the individuals head, though these products still do not meet the same level of sealing as is required for a respirator. Surgical masks are also provided sterile.

Some masks are indicated as dental masks. While these masks are intended for dentistry, there are no physical differences in their construction as compared to other medical face masks.

Finally, some masks have attached shields. These products incorporate a thin flexible piece of plastic at the top of the medical face mask to help protect the wearer’s eyes from splatters of liquids or droplets.

How are Medical Face Masks Constructed? 

Medical face masks are machine-constructed using three to four different layers of non-woven polypropylene. They may have ear loops or ties to hold them in place.

Are Medical Masks Approved by the FDA? 

The FDA considers medical masks a Class 2 medical device and as such they are reviewed using a set of recognized standards. They require an FDA review of the product testing and claims to be cleared for use. Manufacturers and distributors of foreign products must be registered with the FDA. Manufacturer registration must list medical device product (not reviewed by FDA).

How Are Medical Face Masks Evaluated or Tested? 

Medical face masks are evaluated using an industry standard, recognized by the FDA, with the designation ASTM F2100. This standard is a specification for materials used in the construction of medical face masks. The specification includes several test methods and sets criteria in several areas of performance that includes: 

• Bacterial filtration efficiency: the evaluation of mask material filtration to limit the passage of surrogate bacteria suspended in very small liquid droplets
• Particle filtration efficiency: the evaluation of the materials to limit the amount of small aerosol particles from passing through
• Differential pressure: breathing resistance
• Fluid resistance: protection from penetration of blood or potentially infectious liquids projected onto the exterior of the mask
• Flammability: to demonstrate that the product will not burn dangerously, if ignited
• Biocompatibility: the inherent safety of the product for prolonged contact with an individual from the perspective of cell toxicity, dermal irritation, and skin sensitization

While the standard covers several key performance areas, it does not address several other characteristics that may be important for their use and effectiveness. Medical face masks are not evaluated on the following: 

• The standard does not specify minimum sizes for medical face masks and does not evaluate how these products fit on a wearer’s face 
• There is no assessment for how well these products are retained on an individual wearer’s head or the strength of attached ties or ear loops
• There is no test for measuring any particles that come off the masks during use that can be inhaled (referred to as bioburden)  
• Currently, medical masks are not subject to the limitation of any use of certain restricted substances that may pose health or environmental concerns  
• No specific criteria have been developed to examine the effectiveness of face shields for their coverage, liquid or splash protection, or fogging  

One property that deserves additional attention is the fluid resistance of the medical face mask. The test pictured below involves horizontally projecting a small volume of synthetic blood against the exterior of the masks and observing if the fluid can be observed on the interior side. This test is important because differences in fluid resistance are the principal way by which levels of medical face masks are distinguished. 

What Are the Different Medical Face Mask Levels? 

ASTM F2100 establishes three levels of medical face masks based on their ability to resist penetration by a spray of synthetic blood under pressure. The pressures used to project the blood volume are intended to correspond to a range of blood pressure. The ASTM F2100 standard does not indicate how these levels should be used to select different masks for different health care situations, but there are distinctions between the three levels:

Key Takeaways for Medical Mask Use 

Medical face masks are not respirators. While some adjustments, features, or accessories can improve the fit, they do not replace respirators. Medical masks are intended for single use and should be replaced when soiled, damaged, contaminated, or difficult to breathe through. How frequently the mask should be replaced will depend on the circumstances of its use. When saturated with moisture, a medical face mask will be less effective because the mask will be more difficult to breathe through and the saturation can lead to fluids more easily passing through the layers if exposed on the external surfaces.

Webinar Q&A

Participant questions during the webinar were addressed to cover the following safety considerations and best practices for mask selection, use, care, and storage in health care settings.

Are KN95 masks considered to be better protection than more loosely fitting medical face masks?

KN95 masks may have similar filtration efficiency to the filters used in N95 respirators. NIOSH-NPPTL has tested the filtration of some KN95 masks. Some filters perform well while others offer very little protection. Learn more.

Because KN95 masks are made with ear loops, they may not reliably form a seal to the wearer’s face, which is required for true respiratory protection. KN95 masks fall into a hybrid area; some may filter as well as a NIOSH-approved N95 respirator but cannot be considered a respirator due to the loose fit, but many may offer greater filtration and fit than face masks. 

What are the implications of choosing different mask levels? 

It’s important to know what levels of masks are available to you and what procedures might inform your mask choice. Very frequently as an end user, you will not have the option to choose your mask level; you end up using what is in your isolation cart or supply closet. Level 1 masks are fine for most things you do in health care, but if you are performing a task where there is a risk for splash or spray, you can either see if there is a higher level mask available or, even better, add a face shield to your ensemble because a higher level mask can be harder to breathe through, resulting in air flowing around the edges of a mask rather than filtering through the mask.  

What should be done with expired masks? What is important when considering the shelf-life extension on masks? 

If you conduct frequent training on PPE, consider holding on to expired equipment for this purpose rather than throwing it out. 

There is no industry standard for establishing expiration dates. However, variables including storing masks in a temperature and light-controlled environment should maintain their manufactured state. But you should regularly your inventory and replace out-of-date masks. 

How can you prevent your glasses from fogging when wearing a mask? 

While there are products that offer anti-fogging benefits at most eyewear retailers and masks that have a membrane that seals to your face, sometimes you have to step out of the room and dry off your glasses, perform hand hygiene, and then reenter the room.  

How can we address PPE fatigue? How can we engage workers to use PPE correctly? 

There are several ways to encourage workers to continue using PPE correctly. For instance, it can be helpful to record workers during donning and doffing for playback later. This can help people reflect on their PPE use and remind them to adjust their use as needed. It’s important to foster a culture of safety in your workplace by encouraging employees to keep one another accountable. Try offering incentives or celebrating consecutive days of safe PPE use. Finally, consider alternatives to using PPE (sometimes called administrative controls): can you use a whiteboard to communicate with a patient rather than donning PPE and entering the room, keep routinely used equipment accessible in safer areas, etc. 

Should source control be a part of standard precautions? 

There’s no rule against adding additional PPE if you think it’s necessary, based on the risk in the clinical situation. For instance, if you are around an immunocompromised or vulnerable individual you may choose to wear a mask. Guidance on using masks as source control for standard precautions should be a collaborative decision based on perspectives from your safety, leadership, and infection control teams. 

When is double masking appropriate? 

Double masking was sometimes used during the COVID-19 pandemic as an emergency approach to make mask filtration efficiency better, however, it is not a recommended practice. If you are worried about protection from fluid sprays, you would be better off adding a face shield with your single medical mask.  

What should health care workers be wearing for influenza and for COVID-19?  

Consider the risks and if you are at all concerned that there are patients infected with influenza or COVID in your workspace, wear a mask. Prolonged or close contact, or when performing procedures that may induce coughing and aerosols may require respirators and eye protection.