Face masks have been used in medicine and everyday life to prevent the spread of airborne bacterial and viral infections by respiratory droplets for a long time. In light of the recent developments, the importance of wearing a mask in slowing down or preventing the spread of infectious diseases has been a topic of heated discussion. However, there is a great variety of different face masks each with their own purpose and properties.
While doctors and medical professionals are knowledgeable about each type and their intended use, an average consumer is not. The problem is further exacerbated by the misinformation, false opinions and myths about the medical masks spread through social media. Moreover, the initial shortage of the masks in the early stages of the pandemic has led to widespread use of different handmade masks and mask alternatives.
A recent study published in the Science magazine compared different types of commercial and homemade protective face masks in terms of their effectiveness in reducing respiratory droplets and concluded that while N95 and surgical masks significantly lower the spread of the droplets, other measures like neck gaiters/buffs in fact increase the number of droplets by breaking the large droplets into many smaller ones1. In this article we will go over the five key factors to consider when buying a mask to protect against airborne viral diseases:
The first thing to look for when purchasing face masks are the manufacturing standards and recommendations made by the prominent science and medical organizations like the Centers for Disease Control and Prevention, the World Health Organization, Food and Drug Administration (FDA) other reputable institutions. The reasoning behind this is two-fold:
- They are independent sources: While companies and individuals with commercial interests can make unfounded quality and functionality claims, these governmental and international organizations are independent and reputable sources of knowledge
- Backed by science and research: The recommendations made by these organizations are based on decades or research and scientific consensus and backed by solid data and facts.
In this regard, the N95 and KN95 respirators and surgical masks are regulated not only by the CDC but, also National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA).
No matter how many layers of fabric, filters and other protective materials are used in the face mask, it won’t protect you or people around you effectively against bacterial and viral infections if it doesn’t sit properly on your face. In other words, the face mask should be fully covering your mouth and nasal cavity to prevent the respiratory droplets from entering and exiting the area. In this respect, there are several features you need to look for:
- Ergonomic design: A well-designed face mask will fit tightly yet comfortably on any type of face, creating an effective physical barrier between the person and the contaminants in the surroundings.
- Adjustable nosepiece: Since it is crucial to cover both the mouth and the nose for maximum protection, and since every person has a different nose size and shape, the adjustable nosepiece feature is crucial. High quality respirators and surgical face masks come with a durable, soft aluminum stents that can be shaped around the nose for best fit.
- Optimal earloop design: Elastic earloops should be designed tight enough to hold the mask firmly enough for the best protection yet not so tight as to cause discomfort.
Numerous studies have demonstrated that the quality of the fabric characterized by tighter weaving, thicker threads and high thread count is by far the most important factors in increasing the level of protection a face mask provides. These parameters, of course, need to be optimized; for example, a thread count too high will make breathing difficult whereas too few threads will not block the air droplets. The specific material of the fabric (cotton, silk, linen), on the other hand, is of secondary importance.
Another important factor is the number of layers of fabric used in the face mask. High quality face masks contain at least two layers and WHO guidelines recommend a minimum of three layers of fabric for the best protection.
Breathability is a measure of the ability of a fabric to allow moisture vapor to pass through the material, allowing a person to breathe. This, in turn, depends on several factors mentioned in the previous section; thread count of the fabric and the number of layers. For instance, a face mask made of tightly woven satin fabric with high thread count or a mask with four or above layers of fabric will negatively impact the breathability of the mask. It’s also one of the reasons why FDA-approved surgical masks and N95 respirators labelled as “single-use” should not be worn for prolonged periods of time; dust and dirt clog the openings in the fabric, diminishing the person’s ability to breath freely. Impaired breathing not only poses health risks to certain vulnerable individuals but, also makes the mask less comfortable and therefore more likely for people to take them off frequently.
Filter quality factor is a function of the filtration efficiency and breathability factors described in the previous two sections and is by far the most significant measure of the quality of face masks. Commercially available surgical masks and filtering facepiece respirators strive to strike a balance between the filtration efficiency and breathability. In fact, the number “95” you see in the names of KN95 and N95 respirators stand for the filtration efficiency of those masks, which is at 95% (“N” stands for American standard and “KN” stands for Chinese standard). However, while most surgical masks stop the airborne particles of 3 micrometers in size, KN95 and N95 respirators can filter solid particles all the way down to 0.075 micrometers. Needless to say, the filter quality factors of homemade face masks made from various materials are more ambiguous and vary greatly.