Why to use N95 mask? Science behind the scene.

To preserve from pendemic disease, airborne particles we use mask.In current situation: Due to covid-19 doctors and experts recommend to wear N95 mask because it can filter 95% including big particles to nano particle. The thread is charged to attract nano particles and high filtration quality so it is very specific than other masks.

Filteration mechanisms of N95 mask

• Inertial impaction: With this mechanism, particles having too much inertia due to size or mass cannot follow the airstream as it is diverted around a filter fiber. This mechanism is responsible for collecting larger particles.
• Interception: As particles pass close to a filter fiber, they may be intercepted by the fiber. Again, this mechanism is responsible for collecting larger particles.
• Diffusion: Small particles are constantly bombarded by air molecules, which causes them to deviate from the airstream and come into contact with a filter fiber. This mechanism is responsible for collecting smaller particles.
• Electrostatic attraction: Oppositely charged particles are attracted to a charged fiber. This collection mechanism does not favor a certain particle size.
  

In all cases, once a particle comes in contact with a filter fiber, it is removed from the airstream and strongly held by molecular attractive forces. It is very difficult for such particles to be removed once they are collected. As seen in Figure 2, there is a particle size at which none of the “mechanical” collection mechanisms (interception, impaction, or diffusion) is particularly effective. This “most penetrating particle size” (MPPS) marks the best point at which to measure filter performance. If the filter demonstrates a high level of performance at the MPPS, then particles both smaller AND larger will be collected with even higher performance.

This is perhaps the most misunderstood aspect of filter performance and bears repeating. Filters do NOT act as sieves. One of the best tests of a filter’s performance involves measuring particle collection at its most penetrating particle size, which ensures better performance for larger and smaller particles. Further, the filter’s collection efficiency is a function of the size of the particles, and is not dependent on whether they are bioaerosols or inert particles.

Reference;Niosh science.