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A brief introduction to N95 mask related knowledge

Update:29-10-2020
Summary:

N95 mask refers to a mask that meets the NIOSH air filt […]

N95 mask refers to a mask that meets the NIOSH air filtration rating standard "N95" specified by the National Institute of Occupational Safety and Health (NIOSH) and can block 95% of non-oily particles with a diameter of 0.3 microns or more ("N" means "Not resistant to "Oil" is the abbreviation), its biggest feature is to prevent the spread of droplets caused by the patient's body fluid or blood splash. It is the most common self-priming filter respirator. The core technology of N95 masks was developed by Cai Bingyi and Liu Chaoyu in the 1990s. They are professors and doctoral students at the University of Tennessee in the United States. In the 2003 severe acute respiratory syndrome epidemic, the 2013 mainland China air pollution incident and the 2019 coronavirus disease epidemic, the sales of N95 masks in mainland China and Hong Kong increased significantly. In addition, there are also various masks with standards close to or equivalent to N95 around the world.


After N95 masks are in contact with the air, as long as they are not used in the process of producing aerosols and are not contaminated by the patient's body fluids, they can be reused for a limited number of times, but at the same time they also increase the risk of surface contamination by pathogens. At present, OSHA does not have any standards for the disinfection of N95 masks, but NIOSH pointed out that mask manufacturers may give recommendations for the maximum number of re-uses, but in the absence of these recommendations, the maximum number of re-uses for each mask is recommended to be limited to Within five times to ensure safety. CDC recommends not to re-use under normal circumstances, but in emergency situations, such as when masks are scarce, they can be cleaned and purified and used again. People have been trying to explore the cleaning of masks, but there are also concerns that this may reduce the filtering performance of the mask or deform the mask. Researchers at Duke University have published a method for cleaning N95 masks without damaging them, that is, using vaporized hydrogen peroxide, which allows a limited number of reuses. The National Institutes of Health found three disinfection methods that can reuse N95 masks within a limited number of times: hydrogen peroxide, dry heat at 70 degrees Celsius, and ultraviolet treatment. If you use alcohol to disinfect the N95 mask, it will remove the charge in the mask, making the mask unable to absorb particulates, so alcohol cannot be used for disinfection. Steam sterilization and boiling water treatment on top of boiling water have little charge loss and are acceptable.
N95 masks were originally used in industrial industries such as mining, construction and paint, but later to prevent the spread of drug-resistant tuberculosis, they began to be used in the medical industry. In the 1990s, drug-resistant tuberculosis emerged. In order to prevent airborne transmission, N95 standards and N95 masks were widely popularized. Later, medical protection became the consensus of the industry, and the World Health Organization recommended the use of N95 masks to prevent airborne diseases.

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