1) Unless working in an enclosed/unventilated space with heavily infected persons, lone viral particles are relatively rare and have a shorter lifetime in air than if they are in water droplet or aerosol. For someone over 90 with serious health complications a lone virus can possibly cause a problem. If you are 20 something with a robust immune system then you can probably tolerate exposure to a large viral load without any problems.
2) The smaller a particle is, the less likely it is to make contact with a respiratory tract surface on the way in and the more likely it is to be breathed out again.
On the way out, viruses are more likely to attach themselves to drops and aerosols. This means they slightly more likely to make contact with respiratory tract surfaces and more importantly be filtered so the virus sits on the inside of the mask. If the wearer is working in a high viral load area for some time, a significant viral load can then build up on the inside of the mask - this is another reason why they should not be used for too long.
3) The greatest viral loads will usually be on the largest droplets which will be mostly filtered out by even basic face coverings.
4) Viral loads on smaller (aerosols) particles will usually depends on aerosol size but most aerosols will easily filtered by P2/N95 masks.
5) P2 and N95 masks will filter considerable amounts of even <0.1 micron aerosols. They usually perform significant better than their minimum rating (95% at 0.3 microns) and the longer they are are worn, the more they clog up and the finer they filter. I have measured P2 filters with 99.8% filtration at 0.3 microns
6) P3 masks are rated for 99.97% at 0.3 micron - these also filter 99.97% at 0.2 microns and continue to perform very efficiently even at <0.1 microns.
7) The real effectiveness issue for masks is not the filter media efficiency but the reliability of the fit. This is why full face respirators are (or should be) used in COVID wards.
Some of my testing results are here
https://www.woodworkforums.com/f200/.../3#post2188384