• Michael T. Barclay

Effectiveness of a N95 respirator

Updated: Mar 27, 2020

Ever wonder about the effectiveness of a N95 respirator against Coronavirus?

The 'N95' designation means that when subjected to careful testing, the respirator blocks at least 95 percent of very small (0.3 micron) test particles. 

According to recent medical research (reference:, the Coronavirus virions are spherical with a diameter of approximately 125 nanomicrons (0.125 microns) as depicted in recent studies by cryo-electron tomography and cryo-electron microscopy. 

Therefore, the Coronavirus is less than half the size of a particle that can be filtered by a N95 mask at 95% effectiveness.  I think that it’s safe to assume that a N95 respirator is less than 95% effective in filtering Coronavirus.  How much less is not known. 

The point is that the N95 mask alone cannot afford adequate protection against the virus.  Other measure (hand washing, isolation, distancing, etc) are necessary.

However, for an infected person wearing the N95 respirator, it can block or reduce the emissions of Coronavirus caused by sneezing or coughing.   

Also, it does keep the fingers away from the nose and mouth, which can be beneficial in avoiding infection.

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