Personal Protective Equipment is most important in preventing the transmission of a virus, and this is not restricted to COVID-19 treatment centres alone. Of all PPE, it is imperative to know which mask is required for each circumstance, so that protection is effective and there is no unnecessary use of a high-cost mask where it is not required. This will help in ensuring that adequate masks are available according to need, and no shortages occur.
The N95 mask is a Filtering Facepiece Respirator that affords the best protection. As the name itself suggests, it is designed to keep out 95% of airborne particles. Very small particles (0.3 microns) are blocked when the wearer inhales, and unfiltered air is released when the wearer exhales. Like a snorkelling mask, the mask must have a correct facial fit to create a proper seal in order to be effective. The mask is intended to be disposable, but given the current scarcity and cost, researchers are now seeking ways to disinfect the N95 so that it can be re-used by the wearer.
There is also the KN95 mask that has five layers and is rated to capture 95% of tiny particles (0.3 microns). The main difference is that it essentially requires a ‘fit test’. Also, it appears that the ease of breathing is not as good.
An FFP (filtering face-piece) mask is a type of respiratory protective mask that serves to protect against particulates such as dust particles. Of the three classes (FFP1, FFP2 and FFP3), the filter efficiency of the FFP2 replicates the N95 in its use. The mask is a half-face mask, which means that it protects the chin, mouth and nose and has a filtration rate of not less than 94%. The degree of leakage around the edges affects the efficiency of the mask and for this reason, it should be correctly adjusted to the face.
The 3M 8210 is a disposable particulate respirator that is designed to provide reliable respiratory protection of at least 95% efficiency against certain non-oil based particles. This cup-shaped mask is made from polyester with a polypropylene filter. It is fitted with an adjustable nose clip, nose foam and ultrasonically welded headbands.
These masks are strictly intended for healthcare workers. They are not washable and at best can be re-used five times by the same user.
Exhalation valve
Wearing a respiratory protective mask for extended periods of time can become uncomfortable due to breathing resistance and build-up of heat and humidity inside the mask. To alleviate these issues and improve comfort, some masks are equipped with an exhalation valve. This valve allows the exhaled air to escape freely from the mask, avoiding condensation and preventing the filter from becoming less permeable and unpleasant to wear. A mask with an exhalation valve protects the wearer just as well as a mask without a valve.
However, it is important to note that an exhalation valve allows unfiltered air to freely exit the mask. Therefore, in the case of diseases with airborne or respiratory droplet transmission (like COVID-19) a mask with a valve will not protect other people and the environment from the pathogens potentially exhaled by the person wearing such a mask. In these situations, masks without exhalation valves are preferable in order to protect others. Additionally, the exhalation valve might malfunction, which could increase the risk of infiltration of contaminants or toxic dust.
Wearing a respiratory protective mask
In order for the respiratory filter to capture 95% of the particles in the air that pass through it, it must be worn correctly and stay on through the entire exposure. It must fit snugly against the user’s face, ensuring that there are no gaps between the user’s skin and the respirator seal. Facial hair at the sealing area of the respirator may cause it to leak.
Respirators also require a medical evaluation before use because they can make breathing more difficult. Some conditions that could preclude respirator use include heart conditions, lung disease, and psychological conditions like claustrophobia.
Surgical masks
In contrast, a surgical or medical mask is a loose-fitting disposable mask intended to protect the wearer’s nose and mouth from contact with potential contaminants in the immediate environment. It also filters out large particles in the air. Surgical masks also work in the reverse, protecting others by reducing exposure to the saliva and respiratory secretions of the mask wearer. The protection that they provide is limited, as the edges of the mask are not designed to form a seal around the nose and mouth.
The proper surgical mask is the 3-ply face mask that can block out as much as 60 to 80% of particles. The mask is held in place by ear bands and a malleable nose-clip. It is composed of three layers with a specific function for each layer. The outer layer (usually coloured) is a hydrophobic layer that can repel water, blood and body fluids, the middle filter layer sandwiched between the non-woven fabrics is a meltblown material with a high level of static filtration designed to effectively block micro-dust and bacteria, and is said to be the most important layer that also filters out the water droplets. Lastly, there is an inner hydrophilic layer which can absorb water, perspiration and spit. Thus the 3-ply face mask also helps to reduce the spread of viruses, germs, and bacteria.
There is also a 4-ply mask that has an additional layer which is an activated carbon filter. They are more fluid resistant and can ensure secure protection and a maximum bacterial and particle filtration up to 99%. Originally, the activated carbon was used for making masks to counter high pollution. By collecting and filtering out the pollutants and germs they allowed the wearer to breathe in purer air. Newer designs of surgical masks extend upwards to provide an eye shield.
The 2-ply face mask is a hygiene face mask that is cheap and made from fabric, polypropylene or non-woven kind of material. Since there is no filter layer, these hygiene masks offer no protection from airborne viruses. The 2-ply face mask is intended for sanitary and hygienic purposes in a restaurant (mainly for food handling) or spa setting.
Sponge masks protect the wearer from inhaling dust during cleaning processes and are generally worn by housekeeping staff. The unique organic polymer coupled with a three-dimensional planar mesh structure, after fine processing and sewing, constitute a high density of dust blocking at the rate of an astonishing 99% of dust, germs and pollen.
The design is comfortable to wear and protects adults and children alike as the threedimensional modelling structure can fully fit the bridge of the nose. They are attractively designed and aesthetically pleasing. They are also comfortable, having a soft lining and an adjustable ear string and they provide the comfort of easy breathing. It can be washed 3-5 times and the dust isolation rate can still be guaranteed. Washing is done by simple scrubbing with water and no detergent.
Currently, 6-ply masks are flooding the market to meet the demand while providing reasonable protection at a lower cost. These provide a Bacterial Filtration Efficiency and Particle Filtration Efficiency of 95% for 0.3 microns. The outer layer is a coarse particle filter and the inner layer has an antibacterial finish that ensures moisture control. These are backed by a spun bonded layer for droplet protection. The crucial part of the design is a double melt blown layer that acts as a bacteria filter and small particle filter. Like other masks, there is an adjustable nose clip and soft elastic ear loops. The two-panel design is comfortable to wear and accommodates all facial movements. It is also easy to fold and store. They are super breathable and can be hand washed and reused as many as 30 times.
With an acute shortage of mask supplies in the market, many are turning to homemade masks made out of different fabrics like cloth or sponge. Suggested materials are heavy cotton T-shirts, flannel or a tightly woven dish towel. Fabrics with a higher thread count offer a better protection. Various patterns for making a cotton mask have spread around the internet and it is suggested that one chooses a design that has at least two layers of material. While homemade masks do not match the effectiveness of other masks, they are better than wearing nothing to fight the spread of germs, especially during a pandemic situation. Cloth and sponge masks filter out about 50% of bacteria and dust pollutants and are not the best form of defence. They are also required to be washed after every use.
The clear plastic face shield might replace masks as a more comfortable and more effective deterrent to COVID-19. Face shields, which can be quickly and affordably produced and distributed, should extend to below the chin. It should also cover the ears and there should be no exposed gap between the forehead and the shield’s headpiece.
Shields have a number of advantages over masks. They are endlessly reusable; simply require cleaning with soap and water or common disinfectants; are usually more comfortable to wear than masks and form a barrier that keeps people from easily touching their own faces. When speaking, people sometimes pull down a mask to make things easier, but that isn’t necessary with a face shield, which allows visibility of facial expressions and lip movements for speech perception. Face shields are shown to reduce immediate viral exposure by 96%, but there is no indication on how well face shields help keep exhaled or coughed virus from spreading outwards from an infected wearer.
Wearing the mask
It is one thing to select the right mask, but any effectiveness is dependent on how the mask is worn. The mask should be as close to the face as possible – in most designs, a malleable metal piece makes it possible to adjust the mask on the bridge of the nose. As a protection against infectious diseases, the mask is only effective in combination with frequent and effective hand washing. Hands should be washed thoroughly before putting on the mask. The mask should not be touched during use (or hands should be washed immediately). The mask should be replaced when wet. It should be removed by unfastening from the back without touching the front of the mask and then placing it into a suitable closed container before washing hands again.
The sequence for wearing PPE is Apron or Gown, Mask, Eye Protection (if required) and Gloves. For removing PPE, the order is Gloves, Apron or Gown, Eye Protection and Mask.
Compiled by Avril Sule with inputs from Vivek Mata, MD-Charnock Equipments Pvt. Ltd and Dumindu Karunagoda, MD-W.N.J. Imports & Exports Pvt. Ltd
