Amid various qualities of masks available in the market, the question arises as to which one of them is most affective and more importantly, which ones aren’t affective at all.
To come at a conclusion, the material of the mask should be first ascertained. While an N95 or a medical mask is most affective, its authentic variants aren’t being available due to the scarcity among healthcare professionals themselves. It has hence become important to understand the efficiency of the other masks to prevent the spread of the virus and to stay protected from the aerosols as well.
Here, it is important to realize that even if a healthy person is wearing a mask and a covid-19 positive patient isn’t, the percentage of the attendee getting infected is very high as compared to when it is vice versa.
A study from Florida Atlantic University, in Physics of Fluids, from AIP Publishing, looks to better understand which types are best for controlling respiratory droplets that could contain viruses. The research, which was headed by Siddhartha Verma and his team, experimented with different types of materials and designs to determine how well face masks block droplets as they exit the mouth.
They used a mannequin head to demonstrate the cough and sneeze pattern and examine the droplet spread through lasers. This helped them map out the path of the droplets through masks of various materials.
The group found that loosely folded face masks and bandanna-style coverings reduced the distance traveled by the droplet jets from one-eighth to one half respectively of that for an uncovered cough. However, well-fitted homemade masks with multiple layers of quilting fabric and off-the-shelf cone style masks proved to be the most effective. Some leakage notwithstanding, these masks reduced the number of droplets significantly, the study findings said.
Without masks, mannequins were spreading droplets farther than 6 feet.
Mr. Varma further said that his team is continuing experiments to study droplet evaporation, ambient airflow and properties of the respiratory fluid ejected that lead to the behavior of droplets.
“It is also important to understand that face coverings are not 100 percent effective in blocking respiratory pathogens. This is why it is imperative that we use a combination of social distancing, face coverings, hand-washing and other recommendations from health care officials until an effective vaccine is released,” he said.
It has been seen that people belonging to the less financially stable sectors cover their mouths with gunny bags, handkerchiefs, random single layered cloth piece and what not. Quite evidently, these materials do not provide efficacy in staying safe from the virus. While it is to be noted that however, these still give about 2-5 percent protection, a number of ill-effects get dragged along with the use of such ‘masks’.
When selecting a mask, one should be mindful enough to learn about its efficiency against the virus of our concern, i.e. whether it is serving the purpose or not.
In a study conducted in the US, it was found that a certain mask was effective against influenza-like symptoms but not with laboratory proved influenza virus. The types of masks available in the market include N95- can block 95% of micro particles, medical masks- 60-80% efficiency due to loose fit, homemade cloth masks- 50-60% if designed well and homemade with coffee filters- 23-33%.
While N95 is the most effective of them all, surgical masks also provide protection to a great extent. However, it should be noted that both of these are for single-use and must be disposed off after one use.
As far as respirators are concerned, WHO also speaks about its potential benefits and harms, like formation of facial skin lesions, irritant dermatitis or worsening acne, or breathing difficulties that are more frequent with respirators.
Moreover, they should be reserved for healthcare workers and people with co-morbidities if the country or area is running out of them for general public.
Self-contamination due to the manipulation of the mask by contaminated hands, potential self-contamination that can occur if medical masks are not changed when wet, soiled or damaged, skin damage if used for longer hours, uncomfortable, false sense of security with lesser effective materials, and more are factors associated with wearing of masks without taking additional precautions.
WHO says that a recent analysis study showed that either disposable surgical masks or reusable 12–16-layer cotton masks help in the protection of healthy individuals within households and among people who were in contact with covid-19 positive patients.
At present, there is no direct evidence on the effectiveness of universal masking of healthy people in the community to prevent infection with respiratory viruses, including COVID-19.
While medical masks are preferred, non-medical or cloth masks have better accessibility. A non-medical mask is neither a medical device nor personal protective equipment (PPE). It offers around 70% efficiency.
The selection of material is viral and regarded as the basic step to examine its filtration and breathability parameters. Filtration efficiency is dependent on the tightness of the weave, fiber or thread diameter, and, in nonwoven materials, the manufacturing process. The filtration of cloth fabrics and masks has been shown to vary between 0.7% and 60%. The higher the filtration, more is the barrier offered by the fabric. Recent studies show that two non-woven spun-bond layers which are used to make disposable surgical masks provide enough filtration and breathability. Commercial cotton masks are quite breathable but offer less filtration.
Elastic materials too aren’t recommended as they stretch while wearing and lead of increased pore size, giving access to virus particles. Moreover, the filtration capacity os reduced and gets degrade when washed at high temperatures.
A minimum of three layers is required for non-medical masks, depending on the fabric used. The innermost layer of the mask is in contact with the wearer’s face while the outermost layer is exposed to the environment.
Fabric cloths (e.g., nylon blends and 100% polyester) when folded into two layers, provides 2-5 times increased filtration efficiency compared to a single layer of the same cloth, and filtration efficiency increases 2-7 times if it is folded into 4 layers. Cotton handkerchief masks must consist of minimum 4 layers, but show only 13% filtration efficiency. Very porous materials, such as gauze, even with multiple layers will not provide sufficient filtration- maximum of 3%.
It is important to note that with more tightly woven materials, as the number of layers increases, the breathability may be reduced. A quick check for breathability may be performed by attempting to breathe, through the mouth, and through the multiple layers.
The ideal combination of material for non-medical masks should include three layers as follows: 1) an innermost layer of a hydrophilic material (e.g. cotton or cotton blends); 2) an outermost layer made of hydrophobic material (e.g., polypropylene, polyester, or their blends) which may limit external contamination from penetration through to the wearer’s nose and mouth; 3) a middle hydrophobic layer of synthetic non-woven material such as polyproplylene or acotton layer which may enhance filtration or retain droplets.
Mask shapes include flat-fold or duckbill and are designed to fit closely over the nose, cheeks and chin of the wearer.
Coating the fabric with compounds like wax may increase the barrier and render the mask fluid resistant; however, such coatings may inadvertently completely block the pores and make the mask difficult to breathe through. Hence, these are not recommended.
Lastly, it should be realized that a single mask cannot be shared. This will only invite more microorganisms and cross-infections.
According to a recent advancement by a group of scientists from Bengaluru -based Centre for Nano and Soft Matter Sciences (CeNS) under the Department of Science and Technology (DST), masks using static electricity (Triboelectricity) to make more effective covid-19 masks have been proposed.
As a virus has a negatively charged surface, making a mask with its outer layer made of negatively charged materials can help repel the virus.
One has to vigorously rub the mask, made out of non-woven polypropylene cloth (a material used often as grocery store bags), with nylon or silk or wool cloth to create the electrostatic energy, however, no electricity is used.
It can be stitched at home with just a nylon/silk/ woollen cloth placed between polypropylene layers.
The outer layer of the three-layered mask, when rubbed together, develops negative charge while nylon holds a positive charge, thereby creating double-electric-wall protection against viruses.
Nevertheless, more research and lab work need to be carried out to make conclusions on this proposal.
