The N95 mask is one of nine NIOSH-approved particulate protection masks. The "N" denotes not resistant to oil. "95" means that the concentration of particles inside the mask is more than 95% lower than the concentration of particles outside the mask when exposed to a specified number of specialized test particles. The 95% value is not an average value, but a minimum value. n95 is not a specific product name, as long as the product complies with the N95 standard and passes the NIOSH review, it can be called "N95 type mask". An N95 rating means that the filter media is 95% efficient in filtering non-oily particulate matter (e.g., dust, acid mist, paint mist, microorganisms, etc.) under the test conditions specified in the NIOSH standard.
In 1992, while teaching at the University of Tennessee in the United States, Chinese-American scientist Ping-Yin Tsai led a team that developed a positively and negatively charged material that adsorbs 95 percent of microscopic particles, such as dust, bacteria, and viruses, polarizing them before they pass through the mask. This key material was soon used in the manufacture of disposable N95 masks for personal use, and in 1996 the U.S. Centers for Disease Control (U.S. Centers for Disease Control) discovered that N95 masks also attract and block viruses.