One thing we should understand before jumping into the topic is, all those objects we find familiar today on people's face called masks are nothing but sieve plates of higher version.

                                             The evolution of protective face masks ranges from using layers of cotton gauze to layers of charged fibers. They generally filter the air filled with minute particles before entering into our nostrils. This process undergoes three mechanical mechanisms.

• Inertial impaction (collects larger particles)
• Interception (collects larger particles)
• Diffusion (collects smaller particles)

                                                       Let us not get deep into Science. Making it simple, these mechanisms are used to collect particles from smaller to a larger size (higher than 0.01µm).

WHAT MAKES N95 RESPIRATOR OUTSTANDING?

                                         The above three mechanical mechanisms cannot filter some particles. They are called as MOST PENETRATING PARTICLE SIZE(MPPS).In that case, the ordinary surgical mask will not be much efficient in its action. So we go for N95 respirators, which are specialized for filtering out such particles. They have an additional layer of charged fibers as filter media.

                                          In addition to the above three mechanisms, N95 respirators undergo a unique arrangement called 

• ELECTROSTATIC ATTRACTION

                                           Imagine a situation where your body hair is being pulled when your hand is kept in front of your TV screen. Do you remember that goosebumps?. Likewise, this mechanism works the same.

                                            Meaning, particles of opposite charges get attracted irrespective of particle size. The fiber used in N95 masks is charged enough to attract particles regardless of their capacities so that almost all particles are filtered out (even particle size less than 0.01µm). This makes N95 masks specialized in preventing the entry of microbes into the user. 

WHY 'N' AND '95'?

                                              Those numbers represent the rating based on the performance of the respirator in testing. As it filters 95% of challenge aerosol in its action, it is rated as 95.

                                             And the word 'N' in N95 comes based on the level of protection from oil aerosol. Oil aerosol are typical in a particular industrial unit, and it can remove the electrostatic charges from the charged fiber of the respirator.' N.' represents that they are not resistant to oil.