Do oxygen and carbon dioxide move with brownian motion? And, if so, do they get trapped by N95 masks?
Health professionals are experts agree: we should be wearing masks all day when in public during the COVID-19 pandemic, and there are no serious health risks to wearing N95 respirators long-term, unless we have difficulty breathing (eg due to a disability or during strenuous exercise).
That said, I recently learned that N95 masks filter:
- At least 95% of particles that are 0.3 microns
- More than 95% of particles that are larger than 0.3 microns (this is intuitive)
- More than 95% of particles that are smaller than 0.3 microns (due to Brownian motion)
The following chart visualizes this, showing that the minimum fractional collection efficiency is at 0.3 microns. Particles that are both larger and smaller than 0.3 microns are, in fact, both easier to filter.
And, at the same time, the common argument for why masks are safe is that oxygen and carbon dioxide particles are too small to be restricted. Here's some facts about the particles in question:
- The coronavirus is approximately 0.06 - 0.14 microns in size alone 
- Coronavirus is usually attached to other particles making it effectively a larger particle around 1 micron in size or larger 
- Oxygen gas (O2) is 0.000299 microns 
- Carbon Dioxide (CO2) is 0.00065 microns 
So, the question is: do O2 (0.000299 microns) and CO2 (0.00065 microns) travel with brownian motion? And, as such, are >95% of their particles prevented from moving through surgical N95 masks?