Now, I am neither a medical professional nor an epidemiologist; so, I am going to source information from people that are. I am, however, an avid craftsperson. Lately, I have been seeing DIY ('Do it yourself') projects for face masks which are supposed to protect us, as one crafter mentioned in a description on Etsy, "... when viruses and infections attack us."
Surgical Masks Vs N-95 Respirator Masks
So many people are going out of their way to empty stores of surgical masks or the type of "sick masks" that you are likely to find at your local pharmacy. These masks are designed to help prevent splashes and splatter which may contain bacteria and viruses. They are limited and do not provide full protection, but they do offer a barrier that provides some level of protection. Will surgical masks filter out the coronavirus?
The reason being is that viruses are small, and surgical masks are not good at filtering small particles out of the air. This means that coronavirus, and pretty much any other virus, can pass through fairly easily.
The N-95 Respirator masks, on the other hand, are designed specifically to cover your nose and mouth tightly. You then breathe through their filters, which filter out 95% of all particles, including small particles at 0.3 microns. This means that an N-95 mask is able to block viruses from entering when fitted properly most of the time.
Your crocheted mask is useless
So many people are trying to make homemade surgical masks and sell them on sites like Etsy to profit off of this. Please do not buy into this nonsense. It does not matter if there are "4 layers of cotton" or if there is a sleeve to add tissue paper or filter paper into, or if it is crocheted using organic cotton yarn. These WILL NOT protect you against the coronavirus or keep you from spreading the virus.
Spread can occur from virus particles attached to the cloth. If someone else touches, grabs, or shares the cloth, the virus can be transmitted. Additionally, a sick person could still force viral particles through the mesh when coughing. Healthy people that have come in contact with an infected person, can also expel viral particles from the surface of the mask. This is why hospital face masks are supposed to be disposable and not reusable. The surface could be contaminated.
What you can do
The best thing to do to prevent catching or spreading infection is to wash your hands, practice physical distancing, and keep your hands off your face.
Check out this video from the World Health Organization for more information: