An N95 mask is a type of respiratory protective device designed to achieve a very close facial fit and efficient filtration of airborne particles. It is considered a personal protective equipment (PPE) and is commonly used by healthcare workers, industrial workers, and the general public during situations of air pollution, infectious disease outbreaks, and other hazardous conditions. The "N" in N95 stands for "Not resistant to oil," indicating that it does not protect against oil-based particles, while the "95" indicates that it filters out at least 95% of airborne particles that are 0.3 microns in size or larger. N95 masks are made of several layers of materials, including nonwoven polypropylene, meltblown fabric, and electrostatically charged microfibers, that work together to filter out harmful particles. Proper fit and usage are essential to ensure maximum protection.