The global demand for face masks has never been as intense as it is now during the COVID-19 crisis. Almost 9 million people across the world have been infected with coronavirus, and the number is growing by the day. As the infection continues to spread, the use of masks is becoming important not only for medical professionals, but also citizens to stop the spread of the virus.
Since the virus can travel in the form of particles or droplets in the air and stays there for a longer period of time, it is advisable healthcare workers interacting with a coronavirus patient should wear a heavy-duty mask called an N95 respirator. For common citizens, a disposable medical mask is advised to be worn as a precautionary measure.
Factories across the world, particularly in China and India, have stepped up to produce these face masks in bulk to suffice the rising demand of the same. It’s imperative for factories to know the right procedure of its manufacturing right from the type of masks, raw material, accessories to the kind of technology used.
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The virus spreads when infectious aerosol particles are released during breathing and speaking by asymptomatic infected individuals. No masking maximises exposure, whereas universal masking results in least exposure to this infection. Based on function, masks can be categorised into four types – comfort mask, surgical face mask, surgical respirators and particulate respirators.
Commonly used material in mask
Most of the manufacturers who want to foray in mask production don’t have an idea about the kind of raw material that should be used in each of these masks. Below are the five types of fabrics used in making all kinds of mask for medical purpose –
Spun bond fabric for droplet protection
Spun bond fabric is made from PET and polypropylene granules and is used in inner and outermost layer of a mask. The outermost layer generally requires spun bond fabric of 40-50 GSM, while innermost layer is made up of 20-25 GSM. In N95 mask, the outermost layer is made up of 50 GSM and innermost layer is made from 20 GSM of spun bond. While in surgical masks, it is 10-15 GSM on both the layers. The biggest advantage of using this fabric is the softness that it provides on skin. Moreover, this is disposable, air permeable, waterproof and easy to switch fabric.
Meltblown filter for bacterial filtration and particulate filtration
This is composed of super thin and non-continuous fibre which is produced by melting PP granules at a high temperature, and then spraying it to a sheet form. This process makes thin continuous fibres that arrange themselves in such a way that they overlap each other to trap particles but still leave enough open space for air to pass through. Being a filtration layer, this is the most important layer in the mask. These fabrics must have Bacterial Filtration Efficiency (BFE) of at least 99 per cent and Particle Filtration Efficiency (PFE) of 95 per cent or above. Only then these fabrics can be used in respirator.
SSMMS – 5-layer composite that’s a mix of spun and meltblown
These fabrics are made by mixing spun bond and meltblown fabrics, and thus, have acquired properties of both – two layers of spun bond; two layers of melt blown and then one more layer of spun bond. Bacterial Filtration Efficiency in such blended fabrics should be around 95 per cent, while PFE will not be acquired by more than 60 per cent due to its properties. SSMMS fabrics are majorly used in comfort mask which are cost effective.
Activate carbon fabric specifically for pollution filtration
This fabric is made from high quality carbon powder and is used generally to stop inhaling of polluted air. The carbon powder is strategically placed between two non-woven fabrics with less than 2.5 PM insert. The fabric provides following properties – alkali resistance and good conductivity. Apart from the COVID-19 purpose, the fabric can also absorb various industrial exhaust gases such as benzene, formaldehyde, ammonia, and sulphur dioxide.
Hot air cotton for padding and structure
Another type of common mask is made using cotton and low melting polyester blended together by heat. It is used in a mask to provide padding in order to give structure to the mask and stability to the fibres inside it. To make this common mask suitable for a high-level virus like coronavirus, 70 GSM hot air cotton fabrics are recommended for full protection.
Two most commonly used masks and their construction differences –
Surgical mask:It is a loose-fitted, disposable mask that creates a physical barrier between the mouth/nose of the wearer and potential contaminants in the immediate environment. Its construction includes an outer layer of spun bond fabric 10-15 GSM, one middle filtration layer of SSMMS 20-25 GSM, and an innermost layer of spun bond fabric 10-15 GSM.
N95 respirator:It is designed to achieve a close facial fit and provides efficient filtration of airborne particles. Its construction includes an outer layer of spun bond fabric 40 GSM, a 75 GSM hot air cotton layer, 28 GSM 100 per cent pure meltblown fabric, an innermost layer of spun bond hydrophobic fabric 20 GSM, aluminium/plastic nose pin, and an optional respirator valve.
Accessories used for masks
Not just fabrics, medical face mask requires right type of accessories as well to provide comfort on mouth, as these are worn for a longer period of time. Below are the accessories to be taken care of while mask manufacturing –
Ear loop is the most significant accessory in a medical mask which holds it on the face. It comes in knitted and nylon spandex. Nylon spandex provides more stretchability and comfort, while, knitted ear loop is more cost-effective.
Respirator valve forces the air that the mask wearers are inhaling to be pulled through and filtered through the various layers in the mask. As a result, it gives the best efficiency of the mask in terms of respiration. It also helps trapping heat and vapour from exhaled breath which minimises the risk of misting eyewear.
Nose pin is available in both aluminium and plastic. Aluminium is used to provide higher rigidity in mask and it’s a must use accessory, especially in a cup shape mask, while plastic provides more flexibility, especially for foldable masks.
Testing of masks and respirators
As far as trade purpose of masks is concerned, no buyer (both domestic and international) will take untested products, as it’s a matter of the lives of medical fraternity fighting at the frontline against coronavirus. Therefore, mask as a whole will also undergo various testing standards to show what level of filtration it is achieving. However, most of the manufacturers are not aware of these protocols and find it a daunting task to search for the information. The below mentioned parameters of testing may solve the issue for them –
- BFE ASTM F2101: The higher the BFE rate, the better is the protection. It is designed for measuring bacterial filtration efficiency of face masks using Staphylococcus Aureus as the challenge organism. Classification of surgical masks as per BFE in European Standard EN 14683 is as follows:
- BFE ≥ 95 per cent indicates Type 1 surgical masks
- BFE≥ 98 per cent indicates the Type 2 surgical masks
- Breathing resistance EN 13274-3 – 2001 & EN 143: It is used to determine the resistance of airflow through the face mask. The surgical face mask is subjected to controlled flow of air. The difference in airflow pressure of inlet and outlet of the sample is measured and once it is measured, the difference in pressure is then divided by the surface area (in square cm) of the sample. A lower breathing resistance indicates a better comfort level to the end user.
- PFE Test: The Particle Filtration Efficiency (PFE) test evaluates the nonviable article retention or filtration efficiency of filter media and other filtration devices at sub-micron levels. This test is performed on face masks and all filter material that allows one cubic foot per minute (CFM) flow to pass through it.
Here’s the difference of properties between surgical masks and N95:
Surgical mask: Dust filtration, splash/droplet resistance and BFE – 80 per cent each, and PFE – 90 per cent
N95 respirator: Dust filtration and splash/droplet resistance – 99 per cent each, and BFE and PFE – 95 per cent each
Keep watching this space; we will be soon coming up with mask manufacturing technology in the next version of this feature. If you are a mask machine manufacturer and want to get featured here, drop a message to email@example.com to see the procedure of collaboration.
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