Building Air Filters

We know that exposure to wildfire smoke imposes major health burdens.  Especially far from the fire, filtration can play an important role in protecting public safety.  N95 masks have a role, as does staying inside, especially if building air is effectively filtered.  Most homes have minimal built-in air filtration.  Stand-alone HEPA filters can be helpful, though they are difficult to employ for whole-home filtration.  What kinds of products (including existing and new) could facilitate whole-home air filtering?  How should residential building codes be changed to address air filtration?  What about in commercial buildings?