FDA - An N95 respirator is a respiratory protective device designed to achieve a very close facial fit and very efficient filtration of airborne particles.
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. If properly fitted, the filtration capabilities of N95 respirators exceed those of face masks. However, even a properly fitted N95 respirator does not completely eliminate the risk of illness or death.
NIH - The structure of the virus in the cytoplasm of 3-day post-inoculation cells was examined by electron microscopy (Figure 2). Coronavirus-specific morphology was observed. Virus particle size ranged from 70–90 nm and the virus was observed in a wide range of intracellular organelles, especially in vesicles.
N95 masks are likely effective, but that's a lot different than a cloth mask. Even so, we saw many healthcare workers catch COVID, and they were wearing full PPE, including N95 masks.
According to this FDA website,N95 masks block 95% of particles down to 0.3 microns (300 nanometers).
According to this academic paper about the identification of COVID-19, posted on NIH's website, the COVID-19 virus is 70-90 nanometers in diameter.
Actual quotes from sites listed above:
FDA - An N95 respirator is a respiratory protective device designed to achieve a very close facial fit and very efficient filtration of airborne particles.
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. If properly fitted, the filtration capabilities of N95 respirators exceed those of face masks. However, even a properly fitted N95 respirator does not completely eliminate the risk of illness or death.
NIH - The structure of the virus in the cytoplasm of 3-day post-inoculation cells was examined by electron microscopy (Figure 2). Coronavirus-specific morphology was observed. Virus particle size ranged from 70–90 nm and the virus was observed in a wide range of intracellular organelles, especially in vesicles.
N95 masks are likely effective, but that's a lot different than a cloth mask. Even so, we saw many healthcare workers catch COVID, and they were wearing full PPE, including N95 masks.