Also notable is that proper use of an N95 takes training. Unlike with surgical masks, N95 fit is specific (you normally get them sized when issued at a hospital). In addition, most people have bad habits around mask removal - you should always remove masks by the bands, but people tend to touch the mask surface itself. And with any mask removal, you should always wash your hands (in a particular manner that I'm sure readers are familiar with by now). Finally if, when removing a mask, the user touches the interior of the mask after touching an infected surface then reapplying the mask can lead to infection.
Not doing any of these steps can lead to infections. Simply issuing N95s to a general population might not help, if the population is improperly trained.
Surgical masks "work" by preventing the wearer from spreading diseases to others. In aggregate, this can help a population, but in specific cases it might not protect you. N95s work by protecting the wearer, with only secondary benefits to others (the N95s with "nozzles" on the mask surface provide no protection to other parties, as outflow is unfiltered).
The fit thing is difficult, because actually do it properly requires specialized equipment. But for the general population, worrying about that may be letting the perfect be the enemy of the good.
IIRC, that's one of the two methods they use. The "qualitative" gives a binary result, but there are also "quantitative" methods that measure the the actual filtration efficiency with the fit.
That qualitative test kit is probably the cheapest, but it still costs still hundreds of dollars. Though I imagine that's mainly due to low-volume production, since it doesn't seem that complicated.
There are some options for doing fit tests with cheaper equipment. Here's one that uses a humidifier and essential oil diffuser and compares them with the official testing equipment:
Surgical masks also require training. Many people wear masks below the nose. It's often said that this is "malicious compliance", but I've seen them do it outside, in times when even wearing them inside wasn't mandated.
Not doing any of these steps can lead to infections. Simply issuing N95s to a general population might not help, if the population is improperly trained.
Surgical masks "work" by preventing the wearer from spreading diseases to others. In aggregate, this can help a population, but in specific cases it might not protect you. N95s work by protecting the wearer, with only secondary benefits to others (the N95s with "nozzles" on the mask surface provide no protection to other parties, as outflow is unfiltered).