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How to select the right textiles for face masks?

Face masks, face coverings, respirators, personal protective equipment are extremely complex subjects. With the recent global situation, many companies chose to help by transforming their production lines to manufacture these products to respond to the demand.

It is a great responsibility to start producing protective equipment in such a short period of time. Moreover, there is a vast amount of information and misinformation, which makes it even harder for one to navigate through it.

In this condensed article, we intend to share general guidelines on textiles that can be used in non-medical face masks, and which to avoid.

Summary (for non-medical face masks)

  • Non-medical face masks are not meant to protect you from other people. They are meant to protect them from your droplets, by reducing their speed when coughing in particular. They lose more efficiency when they are humid, and they must always be washed with soap and water before reuse.


  • Choose a fabric or a layering of fabrics that will allow the user to breathe easily. Avoid any laminated materials with membranes (such as PUL), coatings, neoprene (also known as scuba knit) as they will block the air from passing through and increase the risks of suffocation.
    Be careful with calendered textiles, as they reduce substantially the amount of airflow. *Calendering is a process where synthetic materials are pressed with a heated cylinder to slightly melt the surface to reduce the airflow through the materials.


  • Select a material or materials that will be dense (higher yarn count per centimetre) enough to reduce the velocity of the droplets when coughing, but not so much that it does not allow to breathe easily. We did not encounter conclusive studies on whether synthetic materials (such as polyester, nylon, polypropylene) or cellulosic materials (such as cotton, hemp, linen, lyocell, viscose) retain for a longer period of time the viruses on their surface, than the other. A study suggests that protein fibers (such as wool, and silk) tend to retain the virus for a longer period of time, in comparison to cellulosic and synthetic fibers.


  • Be careful not to misguide your customers by advertising confusing information.
    1) Antimicrobial / antibacterial properties should not be considered effective on viruses unless proven otherwise, and on a specific strain of virus with supporting documents.
    2) Water repellent finishes do not protect the user from the viruses remaining on the surface of the materials. It only means that if a liquid, such as droplets, would land on the outer material, they would facilitate the repellency of these droplets.
    These finishes must be considered as added values, not as protective barriers.


  • We recommend avoiding trying to meet medical grade face masks testing requirements for non-medical applications. They are highly regulated and require  adequate expertise, because the end user will not be the same. Generally speaking, medical masks are designed to be disposable as the filters lose their efficiency if washed under a regular washing cycle. In contrast,  non-medical face masks are made to be reusable and washable in the machines. We recommend you to focus on developing an easy removal user’s guide to avoid contamination through contact with their hands, along with clear care instructions.



Full details

Medical vs non-medical

The simple approach to determine whether the masks should be considered medical or non-medical is through the specifications that accompanies it. Medical protective equipment is subject to a high level of testing protocols, standards and certifications. While non-medical are not subject to these requirements. This link is a great example of the testing requirements that can be encountered for medical protective equipment: https://buyandsell.gc.ca/speci... (1).



Medical masks

(Such as, but not limited to : N95 and surgical masks)


These masks are not made to kill viruses. They are filters that act like a sieve that blocks certain particle sizes from passing through.


These masks are also combined with protocols to put on and remove them safely to avoid risk of contamination through your hands.


This FAQ from CDC is a great example of how these masks perform.


Do surgical masks provide protection against SARS? Surgical masks are not designed for use as particulate respirators and do not provide as much protection as an N-95 respirator. Most surgical masks do not effectively filter small particles from air and do not prevent leakage around the edge of the mask when the user inhales. (3)

Non-medical mask (homemade)

They do not protect you from the others around you.


They are meant to reduce the risk that you contaminate the others, by reducing the velocity of your saliva particles.


When the mask becomes damp, it loses its protective capacity, and may create a capillarity effect that makes particles transport through materials alongside humidity.


It should always be washed after every use, and the soonest possible after removal to avoid other contamination through contact.


“Cloth face coverings should not be placed on young children under age 2, anyone who has trouble breathing, or is unconscious, incapacitated or otherwise unable to remove the mask without assistance.” CDC, Coronavirus Disease 2019 (COVID-19)

Classes vs levels

Classes do not apply to face masks, they apply to medical grade gowns and they stand for the capacity to block water & viruses. To block these, it also implies that it will block airflow, which is to be avoided for face masks. 
Levels are applicable to disposable surgical face masks.

Recommendation :

Companies that develop these products have worked for years to gain the necessary knowledge to build reliable solutions. We recommend you to focus on non-medical face masks  if you are new in this business,  you do not intend to make it your main focus for the upcoming years, or if you do not have the time to build a reliable supply chain.

Recommendation :

You should consider accompanying your products with:
1. A guideline to indicate how to put it on and safely remove it while not touching the mouth and nose coverage area, to avoid the risk of contamination.
2. Care instructions recommending frequent washes with soap.

What do you need to know about non-medical face masks materials ?

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Don’t

Avoid :
Neoprene (sometimes referred to scuba knit), laminated materials, membranes, coatings.

Be careful with calendered materials.


Why?
As masks are to be worn on your nose and mouth, it is needless to say that you need to be able to breath though. As simple as this may seem, the way that some materials are presented may confuse a misinformed buyer. The above mentioned materials contain a “plastic” layer that blocks air flows.
In a nutshell, it is pretty much like wearing a plastic bag over your head.


PUL stands for polyurethane laminated. This means that the fabric is laminated with a polyurethane membrane which blocks air to go through.


There are two types of polyurethane membranes on the market : non-breathable and breathable. The wording is confusing as in reality both do not let airflow go through. “Breathability” in this case stands for the capacity to transmit vapor through the membrane, not air.

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Materials you can use

We did not encounter conclusive studies on whether synthetic fibers (such as polyester, nylon, polypropylene) or cellulosic fibers (such as cotton, hemp, linen, lyocell, viscose) are retaining for longer amount of time than the others the viruses on their surface.
Although, no matter the time these materials retain viruses, the importance is to wash them at the earliest convenient moment, and always after use.


A study suggests that protein fibers (such as wool, and silk) tend to retain the virus for a longer period of time, in comparison to cellulosic and synthetic fibers.


More layers, means less velocity of the particles, but it also means less airflow.
We would recommend two layers at least, while testing prior to wearing for a longer period of time the breathing comfort of your layer system.

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Careful to the way you are marketing it

Antimicrobials should not be considered effective on viruses unless proven otherwise, and on a specific strain of virus with supporting documents.


Antimicrobial /antibacterial should be considered an added value, but you should be careful when marketing it to your clients, so that they do not confuse it with an antiviral property.
We also recommended being careful to the contact with the skin & airways. Some treatments may contain less recommended components, or even be harmful.


Water repellent finishes are added to the surface of materials to repel water and liquids from its surface, but it is not made to avoid water penetration. Unlike coatings and laminated membranes, water repellents do not affect the breathability of a material, it reduces its absorbency of liquids.


Therefore, water repellent finishes are an added value, and should be carefully marketed to avoid misdirecting the clients. It doesn’t mean that the viruses will not remain on the surface of the materials, it only means that if a liquid, such a droplet would land on the outer material it will facilitate its repellency.
We also recommend using a second layer between your skin and the water-repellent material.


Introduction to textile construction : Non-woven vs woven vs knit

Filters are nonwoven materials which are aleatory placed fibers or filaments (no yarns) maintained together by either : glue, mechanically induced tangles and or heat application.


Filters and nonwovens are mainly developed to control the particles and airflow while materials like wovens and knits are developed for resistance to tearing, abrasion, extensibility, etc. Due to their construction, the integrity of the structure and filtration of nonwovens is more sensitive to cleaning in washing machines. The agitation, water, soap, and heat, can drastically affect the material  by displacing the fibers creating more space for particles to go through, therefore reducing its effectiveness.


Wovens are warp and weft yarns overlapping each other in a regular pattern.


Knits are single orientation yarns (warp or weft) interlacing in loops.

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Confusion between 3D knit and neoprene.

3D knits, also known as a knit with a spacer yarn, are often confused with neoprene for its thick appearance. These knits are composed of two exterior knits linked together by a thicker filament creating an air space in between both sides. While, neoprene is a foam laminated with two knits on the exterior. Therefore, 3D knits allow breathability through the material, while neoprenes block airflow.

Is washing the mask with soap enough to kill viruses?

“Soap dissolves the fat membrane and the virus falls apart like a house of cards and dies.” (4) Make sure to wash properly the masks, not to omit any areas, and note that heat could also increase effectiveness. We invite you to read this article to learn more about this subject: The science of soap – here’s how it kills the coronavirus

We hope this article will shed light on which materials are better suited for face masks, and help you while you focus on helping others.

Annie Cyr & Carlos Agudelo, founders of Tengiva.

References



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