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Everything to Know About Face Masks

What does the number 95 mean on the N95 mask? What are KN95s and KF94s? And how do they differ from a surgical mask? Speaking of which, is it better than an N95 mask? Face coverings of all sorts are a hot topic right now, and now in vain- we all want to be as protected as possible. In this article, we'll answer all those questions, and for the history enthusiasts among you, we'll also cover the origins of the N95 respirator. 

Practicality first- how many times can you use one N95 before discarding it? 

N95 face mask N95 respirators manufactured by 3M to meet the U.S standard.
There are no official expiration dates published by any manufacturer. However, there are some general guidelines published by the CDC to help you decide when the mask has to go in the trash. 
  • If there are stains or the mask is dirty, discard it. 
  • If the mask is compromised or it is deteriorating, discard it. 
  • If the mask is wet, or has been wetted, discard it. N95 masks cannot be washed or laundered. 
  • If the straps are loose and the mask doesn't fit snugly, discard it. 

face mask KF94KF94 respirator, the South Korean standard. 

In October 2020, there was a mask shortage. The CDC then published guidelines for health workers, for how to make the most out of their face masks while avoiding pathogen risks. When there aren't mask shortages, health workers use a new mask daily. The guidelines are as follows:

  • Have 5 masks in rotation, each stored in its own breathable container- either a paper or mesh bag.
  • Use one mask daily, hang it at the end of each day. 

This regimen allows 5 days for any pathogens that landed on the mask to die off. As for how long should you keep the mask in rotation, the CDC recommends 5 wears for every mask. 

How can I recognize a legitimate mask? 

KN95 face mask KN95 respirator, the Chinese standard. 
According to the San Francisco Chronicle, a legitimate N95 mask will have a manufacturer's name and model number on it. It has a layer of tight polypropylene fibers, which block 95% of airborne particles (thus the name N95) and create an electrostatic charge to enhance particle filtering. 
At this point, it is important to stress the difference between a respirator and a surgical mask. While the surgical mask is made to prevent the wearer from coughing droplets into the air, a respirator such as the N95, the KN95, or the KF94 actually filters your breath. A surgical mask fits loosely around the face while a respirator fits more snugly. 

Origins of the N95

spanish flu hospital
Medical staff wearing Wu's cotton and gauze mask. 

For many centuries, it was believed that stench and foul smells are what causes one to get sick. You can read all about how this belief changed here- The Great Stink of 1880. This logic is what led humanity to the infamous plague masks that look like beaks. These beaks were filled with incense and perfumed herbs, with the belief that as long as the doctor breathed nice smelling air, he would be protected from illness. 

But as we all know, with the progression of microbe studies we learned that it takes more than a foul odor to make a person sick- it makes contact with a pathogen. And so in 1897 surgeons started wearing the first surgical mask. It was simply a handkerchief tied around the face, meant to prevent the doctor from sneezing or coughing micro droplets into the patient's open body.

men wearing a face mask on the street, 1918Source/Men wearing a cotton and gauze face mask on the street during the Spanish flu, 1918. 

In 1910, a plague spread in Northern China. The Chinese Imperial Court brought in a doctor named Lien-teh Wu, who performed an autopsy on one patient and concluded that this plague is airborne, and not transferred by fleas, as was presumed by all. He improvised a mask of gauze and cotton that quickly spread throughout medical and army personnel and became the symbol of the plague. When the Spanish flu burst in 1918, the public was quick to sport this mask. 

At the beginning of the 1960s, a company called 3M (one of today's N95 manufacturers) was developing and experimenting with substances. They created a sturdy fiber that could be made into a non-woven fabric (like felt). They molded it to create many things, from ribbons that wouldn't tear to bra cups, and, eventually, a bubble shaped dust mask. Its shape was inspired by the bra cup. Can you see the resemblance in today's N95? 

According to Fast Company, "The first single-use N95 “dust” respirator as we know it was developed by 3M, and approved on May 25, 1972." Two decades later, in 1992, Dr. Peter Tsai found that adding static charge to the filter would draw pathogens into the filter, thus ensuring its filtering. It took several more years until the mask earned its popularity, and today, it is declared the gold standard in the USA. 

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