Arney is correct (see my previous post). But there is more to it than that.

Now, in an ideal world the N95 is plenty good enough for filtering most harmful particles. In reality, especially if dealing with something like heavy air pollution (be it from a fire or something else) it won't last very long. The N95 is a DISPOSABLE, one-shot mask. Made of cheap materials that don't last long. What few people realize is that dust tends to be highly abrasive. It will degrade the cloth-like fiber structure quickly, clogging it at first then tearing it gradually on a micro level. All of which leaves you more and more exposed to the pollutants even though you won't know it and won't have any objective way of measuring it.

Second, the mask will degrade rapidly when in contact with sweat and body heat. Not such a big deal as long as you sit still but it becomes important if you are physically active. Moreover, strenuous activity will have a negative impact on the fit. Gaps will appear and once that happens you can forget about the 0.3 micron thing.

The N95 does what it was supposed to do pretty well but its real purpose is quite limited. Some folks seem to believe it's a quick fix for everything. Well, it's not. Also, it's called a disposable mask for a reason. Meaning that any situation that involves higher risk, longer duration exposure to irritant or harmful particles calls for a more complex and better made (and more expensive) mask.