Close enough and with enough pressure you can blow a hole in almost anything. I'm usually running about 75 PSI and use a generic rubber-tipped air nozzle and squirt air from about a foot or so away. I clean the shop vac filter that way too. The specs on paper filters are for AVERAGE pore size, which means that there are pores that are considerably larger. Try looking through a K&N filter after you've cleaned and oiled it. You can see the light coming through the holes like it was a dry shake roof. If you see those holes in your paper filter, throw it away. And for pet's sake don't use the HRL disposal method in fire season. All this discussion is why I prefer oil bath air cleaners, mostly I'm cheap and they work fine.
When Mt. St. Helens blew its top forty years ago, the state patrol cars got retrofitted with big, external-mounted truck air filters with cyclone elements to spin out the dust before it went into the filter. These were mounted on the front bumper with what looked like dryer-vent hose going to the carburetor. The civilian cars with only the factory paper filters died a terrible death and ended up in wrecking yards in short order.
