WHO gave Corona Virus, a name that is Covid-19. Last week I have published a blog about one of the protection methods, that is wearing a surgical mask. In that blog I tried to cover different aspects of mask like What is a surgical mask?, Why masks are use?, What are standards for a mask to be acceptable and What is its effectiveness against Covid-19?. Many of my readers asked me to write about a way to test a mask on the spot or at least before buying in bulk. Therefore, I have decided to write a blog on how to test a mask. Now a days Covid-19, is the most scary thing every one is talking about. How it is spreading?, how to protect from it?, how to contain the spread of this virus? and Is there any cure or vaccine for it? These are the questions almost everyone is looking answers for. Because now a days everyone is looking for a mask consequently with a boost in demand, many fakes also made their space in the market. Therefore, in this blog I will try to explain my readers how you can test a mask by yourself and judge the quality before buying. Remember, this is very important because it is directly related to your health. To make a background for those who have not red my previous blog on “Covid-19 and protection from mask” I am going to include some important contents from my previous blog those are related with testing of masks.
The structure of a surgical mask
A surgical mask is typically composed of three layers. 1) Outer-layer 2) Middle-layer 3) Inner-layer. In addition, there are elastic ear loops and aluminium metal nose strip to facilitate the better fixation of mask on the face. The main function of outer layer is to provide with primary air filtration and to somehow air regulation. the middle layer serve as a filtration barrier and the inner layer should ideally provides comfort by dissipating the heat and moisture created by exhaling breath. However, in my experience this function is not achieved with a common surgical mask. Moreover the three layers have usually three folded lines to facilitate the fit of the mask and to provide maximum coverage from nose to under jaw of the wearer. When the mask is pulled down after fixing on nose, because of the these folded portions a room in the shape of a polyhedron is crated between mouth and nose which helps to mitigate the feeling of oppression. The photo below shows the components of a mask as described above.
Surgical Mask–How to test a Surgical Mask Before Buying and using?
To test the mask, I decided to buy some from the market and test them by myself. Obviously one cannot conduct all those laboratory testings however, I can do at least some checks before using. This is important because it is related to your health. In order to do a comparative study, I bought a good quality one and a comparatively low quality.
- Mask protection level Information and packing
The two masks have same quantity in the box that is 50 masks in one box. However, the good quality mask has individually packed masks in a wrap with a lot of information on it as shown in the figure below. The information on the good quality mask tells about the standard to which this mask qualifies and the protection level. It also tells that the mask is hypoallergenic, latex free and fiber glass free. Hypoallergenic, meaning “below normal” or “slightly” allergenic. Latex free means the elastic ear loops are latex free ad fiberglass free means that there is no fiber glass is used in making the mask fabric which can be allergenic to some people. On top of that the information on the good quality mask also tells us about the bacterial and particle filtration efficiency of these masks. On the other hand, there is no such information available on the packing of the poor-quality mask. Therefore, while buying the mask you should check the packing of mask and must check the standards and other information as described above. Now let’s proceed towards other checks on the quality of mask.
2. Fit and size test
To test the fit of mask on your face the first thing you should consider is to check the size of your Nose to bottom of lower jaw bridge length and decide which size will suits you. The following figure shows how to measure your Nose to bottom of lower jaw bridge length. After knowing your size, you can check that either the mask you are going to buy fits you or not after opening of folded sections.
Once the size is measured, then you can put on the mask on your face and pull it downward to cover your Nose-lower jaw bridge. After covering the whole area just fix the aluminum nose wire on top of your nose such that there is no gap between top side of mask and your skin. After that check the sides of mask near your ear there should not be any gap between mask inner surface and your skin. Similarly check the area under lower jaw there should also be no gap between mask inner surface and your skin. This test means that the mask should provide complete seal from all sides and there should not be any gap that can possibly allow contaminant air to enter. If there are different sizes available in the market, then most important is choosing right size. However, if the right size also do not fit will and do not provide air tight seal from all sides on your face then the quality of mask in terms of fit is not acceptable.
3. Liquid droplet penetration test
After conducting the fit test you can conduct a Liquid droplet penetration (LDP) test. This is very critical because it has been established that the novel Corona Virus travels in liquid droplets and can be transmitted via liquid droplets. When an infected person sneezes and you are nearby, the virus can transmit in the liquid droplets coming out of sneezing and chances of inhaling virus by you are very high. Therefore, among all other features this is most important and must not be compromised. To test LDP, you can just put a mask on a smooth surface with the outer layer that is mostly colored side, facing toward you. Now drop some water drops by using a dropper or just by your hand. For a mask to qualify LDP test these droplets should not penetrate into the outer layer and should stay on the surface. However, remember if you will put some pressure or try to rub the water drop they will be absorbed or penetrated into the fabric, this is something to do with the surface tension of water drop and micro structure of the fabric, which I am not going to explain because it is out of scope of this blog. What you need to know is the water droplets should not be penetrated or absorbed on their own without any rubbing or any pressure.
Above is the figure of a good quality mask which I bought from the market. The poor quality mask failed the LDP test therefore, it can be stated that there are fake masks available in the market very easily. So you should be careful and must perform LDP test before using a mask especially if you are in a contagious environment where chances of inhaling virus are high.
4. Testing the three layers
After LDP, you can test the quality of mask by observing each single layer. Generally, the outer and inner layers of a mask should be spun-bonded poly polypropylene non woven fabric having a GSM of 20-25 while, the middle layer should be melt-blown with a little higher GSM of 25-30. Obviously every person cannot know the GSM of fabric just by touching or feeling it, for this one need to have a sensitive weighing balance and need to know how to calculate the GSM of a fabric. However, you can just compare the different available qualities. Just take a paper cutting knife and cut open the three layers of both masks, then compare them layer by layer. The more poor is the quality the more transparent or see through the fabric is. A good quality has enough fiber contents per unit area and do not look like a see through or transparent fabric. Below figures show a comparison of three layers of a good quality mask and a poor quality mask which I have bought from the market for comparison. The most frightening observation which I have made is that the good quality mask has a very thick filter layer that is middle layer and the poor quality mask has a very thin or an open/see through middle layer as shown in the figure below. Surely, such a poor quality mask cannot protect you from any infection. Same was the case with other two layers.
5. Strength test
After testing all above features, you can quickly conduct a strength test of a mask, the strength of mask is not so critical as compared to the other features because it is a disposable item. However, a mask should at least have enough strength so that it can be used for 8 hours continuously that is a normal period of working hours for almost every one. To test the strength just try to tear a mask with three layers altogether. You will find it difficult to tear a good quality mask because of enough fiber contents as compared to poor quality mask with too little fiber contents as shown in the figure below.