i had to learn about N95s when OSHA's new Silica in Construction rule went into effect a couple years ago. For them to perform as specified, there's a lot more to it than just buying and wearing one.
Fit test. A trained & licensed mask tech checks several makes and models of N95 half-masks on the user to find the best fit for that person. The user is given a card to carry showing the make & model number they'll need to use.
Quick user fit test. Once a mask is selected, the user dons one and sharply inhales as much and as quickly as possible. When properly fit, the mask will suck up hard to his face, much like a solid covering would do. The user is instructed to perform this test every time he puts it on or adjusts it to insure its performance.
Qualitative fit test. Also performed by the mask technician. The user dons and fits his mask, and is instructed to open his mouth and stick out his tongue (inside the mask). The tech then uses a nebulizer containing one of 4 approved test vapors (bitter, sweet, etc) and sprays the test vapor a specified distance from the mask, counting the metered doses until the user reports he can taste it. Each vapor type has a specified number of doses required to be acceptable. This test must be repeated annually.
The user must understand that the mask is a filter, and to be effective, 100% of their breath must pass thru it, with no leaks around the edges. That means facial hair, even a mid-day stubble, is out.
The above is what a construction worker exposed to respirable, crystalline silica dust is now required to go thru. Keep in mind that silicosis is a cumulative disease that often takes years of exposure to manifest. That bears little resemblance to virus protection, where a single exposure could prove fatal.
The N95 specification requires them to catch at least 95% of respirable particles down to 0.3 microns in size. A naked covid particle (called a virion) can run from 0.06 to 0.14 microns, plenty small enough to penetrate an N95. Fortunately, virus particles of concern (those expelled with an infected person's cough, sneeze or speech) are encapsulated in spit/phlegm/body fluids, increasing their size to above the 0.3 N95 spec. The 95% @ 0.3 spec is the minimum requirement, and most N95s actually exceed that by a decent safety margin.
N95 users in construction that do it right typically hate them. Properly fit, they're pretty hard to breath thru at rest, and really bad when working enough to breathe hard. It's bad enough that concerned employers are spending a lot of money on alternative methods (like wet saw cutting & HEPA vac attachments on concrete drills).
Bottom line, if your N95 leaks around the edge (even just a little bit), they're no better at preventing COVID19 spread than a surgical mask.