The filtering function of a KN95 mask
relies on multiple components and layers working together to trap and filter airborne particles. The main parts of the filtering function of a KN95 mask include:
Outer Layer: The outermost layer of a KN95 mask is typically made of non-woven fabric. While it primarily provides structural support and durability to the mask, it also offers some protection against larger particles, splashes, and droplets by acting as a physical barrier.
Middle Filtration Layers: The heart of a KN95 mask's filtering function lies in its multiple middle layers, usually made of melt-blown fabric. These layers are responsible for capturing and filtering out small airborne particles, including dust, fine particles, bacteria, and viruses. Here's how these middle layers work:
Electrostatic Charge: Melt-blown fabric is electrostatically charged during manufacturing, creating a strong attraction to particles carrying an opposite charge. This electrostatic attraction helps trap particles even smaller than the gaps between the fibers.
Particle Capture: As air passes through the middle layers, particles are trapped by the dense network of fibers. The smaller the particle, the more likely it is to be captured due to the electrostatic forces.
High Filtration Efficiency: The melt-blown layers provide a high filtration efficiency, meaning they can filter out a significant percentage of particles, including airborne pathogens like viruses.
Inner Layer: The innermost layer of a KN95 mask is usually made of non-woven fabric as well. This layer is in direct contact with the wearer's face and is designed for comfort. It helps absorb moisture from the wearer's breath, making the mask more comfortable to wear for extended periods.
Nose Bridge: Many KN95 masks include a flexible nose bridge or metal strip that can be shaped to fit the contours of the wearer's nose. This not only improves comfort but also helps create a secure seal, minimizing gaps through which unfiltered air could enter.
Ear Loops or Headbands: KN95 masks come with either ear loops or headbands to secure the mask to the wearer's face. Proper adjustment of these straps ensures a snug fit, enhancing the mask's overall effectiveness.
Exhalation Valve (Optional): Some KN95 masks
are equipped with an exhalation valve to make exhalation more comfortable for the wearer. The valve opens when the wearer exhales, allowing air to exit more easily. However, masks with exhalation valves may not provide source control, making them less suitable for situations where protecting others is also a concern.