The N9S type mask is one of the 9 types of anti-particulate masks certified by NIOSH (National Institute for Occupational Safety and Health). "N" means not suitable for oily particles (the fumes produced by frying are oily particles, while the droplets produced by people talking or coughing are not oily): "95" means that the filtering efficiency reaches 95% under the testing conditions specified by the NIOSH standard. . The mask is commonly used for occupational respiratory protection, including certain microbial particles (e.g., viruses, bacteria, mold, etc.). Its most important feature is that it can prevent droplet infections caused by patient body fluids or blood splashes. The U.S. Occupational Safety and Health Administration (OSHA) for healthcare organizations requires that medical personnel exposed to tuberculosis bacteria must wear a mask with an N95 standard or higher.